i

Grazing Winter and Spring Wheat Crops Improves the

Profitability of Prime Lamb Production in Mixed-Farm

Systems of Western Australia

Eman Ali Hussein

Supervisors: Dr Dean Thomas (CSIRO)

Associate Professor Dominique Blache (School of Animal Biology, UWA)

Faculty of Nature and Agricultural Science (FNAS), The University of Western

Australia (UWA), 35 Stirling Highway, Crawley, WA 6009.

This thesis is presented to the FNAS, UWA as a partial fulfillment of the requirements

for the degree of Master of Science (Animal Science) by way of Thesis and

Coursework, Thesis Paper: SCIE 9721-9722, and formatted to the requirements of the

Animal Production Science.

July 2012

ii

Statement of candidate contribution

I, Eman Ali Hussein, declare that the thesis hereby submitted for the Master of Science

(Animal Science) by way of Thesis and Coursework degree at The University of

Western Australia is my own work and has not been previously submitted by anyone or

me at another university for any degree.

All contributions made by other individuals have been duly acknowledged.

Eman Ali Hussein

July 2012

iii

Acknowledgments

I would like to express my special thanks of appreciation to my supervisors Dr Dean

Thomas (CSIRO) and Associate Professor Dominique Blache (UWA) for their constant

support, invaluable guidance and motivation that has encouraged me to come up with

this project. I greatly appreciate help of Dr Thomas for his answers to my endless

questions and his commitment to making time for his students is gratefully

acknowledged

I am very thankful to the Commonwealth Scientific and Industrial Research

Organisation (CSIRO) for the opportunity to undertake this research within the

organisation. I wish to thank all the staff from the CSIRO Livestock Industries Division

and the staff in UWA in particular school of Animal Biology and FNAS, with the help

of their valuable suggestions, guidance and encouragement; I was able to perform this

science project. Without you this effort would not have been possible.

I thank the staff from the CSIRO Information Technology (IT) for their continued

technical help throughout the past year. I am grateful to Dr Lindsay Bell and Mr Eric

Zurcher for their time, expertise and advice with the APSIM model. In addition, I wish

to thank my friend Doraid Amanoel for his helpful suggestions and friendly

encouragement.

I am pleased to acknowledge my sponsors, AusAID, for providing Australia–Iraq

Agricultural scholarship (AIAS) and research funding for completion of this thesis.

Last but not least, I am truly appreciative to my family for their unending support and

encouragement throughout my academic years.

iv

Table of Contents Statement of candidate contribution ............................................................................. ii

Acknowledgments ......................................................................................................... iii

Table of Contents ........................................................................................................... iv

Table of Figures ............................................................................................................. vii

Abstract ............................................................................................................................ 1

Introduction ..................................................................................................................... 3

Aims .................................................................................................................................. 6

Significance and outcomes .............................................................................................. 6

Chapter One .................................................................................................................... 7

Review of the literature .................................................................................................. 7

Summary ........................................................................................................................... 7

Australian sheep industry ............................................................................................... 8

The Australian lamb industry ............................................................................................ 8

Lamb market specifications ............................................................................................... 9

Lamb production systems ............................................................................................. 10

Joining and lambing time ................................................................................................ 10

Lamb nutrient requirements ............................................................................................ 11

Feedbase in lamb production systems ............................................................................. 13

Feedbase quantity ....................................................................................................... 14

Feedbase quality ......................................................................................................... 15

Factors affecting the lamb industry ............................................................................. 17

Climate conditions .......................................................................................................... 17

Drought ........................................................................................................................... 18

Feed shortages ............................................................................................................ 20

Fluctuations in lamb price .......................................................................................... 20

Lamb finishing systems ................................................................................................. 21

Economics of lamb production ........................................................................................ 21

Management strategies to overcome feed deficit ............................................................ 22

Grazing cereal crops ....................................................................................................... 24

v

Grazing wheat crops ..................................................................................................... 24

Advantages of grazing wheat crops ................................................................................ 25

Management of animal grazing on wheat crops ............................................................. 26

Farm system simulation modelling .............................................................................. 26

Conclusion ...................................................................................................................... 27

Chapter Two .................................................................................................................. 28

Materials and Methods .................................................................................................... 28

Weather and soil ......................................................................................................... 29

Stocking rate ................................................................................................................ 30

GrassGro model .......................................................................................................... 30

Model farm and pasture management ......................................................................... 30

Livestock management ................................................................................................ 31

APSIM model .............................................................................................................. 32

Wheat crops management ........................................................................................... 32

Livestock management ................................................................................................ 33

Spread sheet analysis .................................................................................................. 34

Grazing wheat crop varieties analysis ........................................................................ 34

Gross margin ............................................................................................................... 34

Statistical analysis ........................................................................................................... 35

Chapter Three ............................................................................................................... 36

Results ............................................................................................................................ 36

The duration of cereal grazing ........................................................................................ 36

Effects of grazing wheat crops on supplementary feeding cost ...................................... 37

Effects of grazing wheat crops on lamb production enterprises profit ........................... 38

The relationship between the change in supplementary feeding cost and duration of

grazing wheats ................................................................................................................ 41

The timing of wheat cereals grazing ............................................................................... 42

Chapter Four ................................................................................................................. 45

Discussion ....................................................................................................................... 45

Profit from grazing dual-purpose winter wheat versus spring wheat cultivar ............... 47

How often will wheat crops provide a winter forage resource? ..................................... 48

vi

Estimating farm profit ..................................................................................................... 49

Key assumptions .............................................................................................................. 49

Conclusion ...................................................................................................................... 51

References: ..................................................................................................................... 53

Appendix 1 GrassGro farm system components ............................................................ 64

Appendix 2 APSIM stimulation model: farm system components and weather data file

example ........................................................................................................................... 65

Appendix 3 Grazing wheat crops output report generated using APSIM simulation

modelling ......................................................................................................................... 66

Appendix 4 Journal Formatting ...................................................................................... 67

vii

Table of Figures

Fig. 1. Typical feed gaps in two regions in Western Australia highlighted by the

shaded areas. Long term average monthly ME (MJ/ha/day) supply from pasture

(line with black circle) and the demand (line with white circle) for ME by a typical

beef cattle breeding enterprise. ................................................................................ 15

Fig. 2. The relationship between DMD and live weight change of ewe ........................ 17

Fig. 3. Green and dry feed on offer in three rainfall zones in Western Australia .......... 18

Fig. 4. The five lowest rainfalls on record in Southwest Western Australia: Bureau of

Meteorology, Western Australia Climate Services Centre 2010. ............................ 19

Fig. 5. Simulated cummulative distribution of the profitability of lamb production

enterprises (expressed as gross margin $/ha) when wheat crops were grazed at three

locations in Western Australia. Each curve comprised 50 seasons from 1960 to

2009. ........................................................................................................................ 40

Fig. 6. Simulated cumulative distribution of the profitability of lamb production

enterprises (expressed as gross margin $/ha) with or without grazing of wheat crops

(winter and spring) at three locations in Western Australia. Each curve comprised

50 season from 1960 to 2009. .................................................................................. 41

Fig. 7. The relationship between wheat crops (winter and spring) grazing days and the

change in supplementary feeding costs at the three sites of Western Australia. The

solid line is the regression line fiteed between change in supplementary feeding

costand DSE grazing crops. ..................................................................................... 42

Fig. 8. Long-term average monthly distributions of grazing wheat cereal varieties in

DSE days/ha at (a) Kojonup, (b) Wickepin and (c) Merredin. Dual-purpose winter

wheat culivar (grey fill); Spring wheat cultivar (black fill). Data were averaged for

50 seasons from 1960-2009. .................................................................................... 44  

viii

List of Tables

Table 1. Western Australian locations (high, medium and low rainfall) used in the

grazing wheat crop simulation modelling study ...................................................... 29

Table 2. Meat, wool and grain prices and other costs used in the analysis ..................... 32

Table 3. The proportion of years that wheat crops (winter and spring) are grazed and the

average duration of grazing wheat crops in those years where wheat crops grazing

opportunity occurrs in the three regions of Western Australia ................................ 36

Table 4. Supplementary feeding costs in a prime lamb enterprise without and with the

grazing of winter and spring wheat crops at three locations in Western Australia.

DP, Dual-purpose wheat variety .............................................................................. 37

Table 5. Annual farm gross margins predicted by simulation modelling. With dual-

purpose (DP) winter wheat grazing (WG), spring wheat cultivar grazing (SG) or

without grazing (NO G) ........................................................................................... 38

0

Grazing Winter and Spring Wheat Crops improves the

Profitability of Prime Lamb Production in Mixed-Farm

Systems of Western Australia

Thesis paper

Eman Ali Hussein

Supervisors:

Dr Dean Thomas (CSIRO)

Associate Professor Dominique Blache (School of Animal Biology, UWA)

Faculty of Nature and Agricultural Science (FNAS), The University of Western

Australia (UWA), 35 Stirling Highway, Crawley, WA 6009.

This thesis is presented to the FNAS, UWA as a partial fulfillment of the requirements

for the degree of Master of Science (Animal Science) by way of Thesis and

Coursework, Thesis Paper: SCIE 9721-9722, and formatted to the requirements of the

Animal Production Science.

July 2012

1

Grazing Winter and Spring Wheat Crops Improves the Profitability of

Prime Lamb Production in Mixed-Farm Systems of Western Australia

Eman HusseinA Dean T. ThomasB and Dominique BlacheC

AFaculty of Natural and Agricultural Sciences, The University of Western Australia, 35

Stirling Highway, Crawley, WA 6009, Australia. B CSIRO Animal Food and Health Sciences Division, Centre for Environment and Life

Sciences, Underwood Avenue, Floreat, WA 6014, Australia. CSchool of Animal Biology, The University of Western Australia, 35 Stirling Highway,

Crawley, WA 6009, Australia.

Abstract

Lamb production in Western Australia has historically been constrained by both within

and between season fluctuations in pasture productivity and its frequently low

availability and poor nutritive value during the autumn-early winter. Hence, there is a

need to investigate alternative feed components that could potentially mitigate feed gaps

and increase farm profitability. Grazing immature cereal crops, particularly different

varieties of wheat, has become widely used in the high-rainfall areas of southern

Australia. Recently, there has been growing interest in applying this technology in drier

parts of the mixed-farming zones of Western Australia.

A modelling study was conducted to examine farm business returns with or without the

grazing of immature wheat (winter and spring varieties) in different locations of

Western Australia. Results from a combination of the GrassGro (pasture and livestock

simulation model) and APSIM (crop simulation model) were used to evaluate the

changes in farm gross margins with the grazing of cereal crops at three locations of

Western Australia (Kojonup, Wickepin and Merredin), representing the high, medium

and low rainfalls respectively. In this simulation modelling, the lamb production system

was based on a Merino ewe enterprise producing crossbred lambs (Poll Dorset ×

Merino), which were then sold as finished lambs at 45 kg live weight. We used 50

2

years of daily-based climatic data from 1960-2009 for the three study sites. Grazing

wheat crops commenced only when green pasture biomass was less than 800 kg/ha.

The results of the simulation study suggested farm profit can increase by grazing both

winter (mean value A$ 26/ha) and spring (mean value A$ 5/ha) wheat crops across all

research locations and averaged for all years (in many seasons no crop grazing

occurred). The simulation study found that grazing the two wheat varieties (winter vs

spring) at the high rainfall location increased the profitability of the livestock enterprise

by 2.5 times more than grazing crops at both low rainfall locations (P<0.05).

On average, across all years, supplementary feeding costs were reduced at the three

locations by the inclusion of grazed winter (17%) and spring (3%) wheat crops in lamb

production system. However, the comparative reduction in the cost of supplementary

feeding varied between and within locations that integrate the two wheat cereal systems.

These variations were due to both the frequency and average duration of the grazing of

wheat crops in these regions, and the farm-stocking rate. Both wheat varieties were

frequently grazed at Merredin (65% and 31% of years for winter and spring wheat

varieties respectively), while grazing spring wheat was less frequent at the higher

rainfall location and averaged 16% of years due to a greater difference in the relative

availability of wheat crops versus pasture for grazing among regions. Overall, this study

found that wheat crops are likely to supply green feed during the winter feed shortage

(April-July) and reduce supplementary feed requirements for a short period of time in

some seasons.

Key words

Simulation, modelling, prime lamb production, spring and winter wheat, dual-purpose

wheat, farm profit, supplementary feeding.

3

Introduction:

The focus of this study is the grazing of wheat crops and its role in prime lamb

production system in Western Australia, mainly, during the period of winter feed

shortages. Over the past decade the Australian sheep industry has expanded in response

to increasing demand for lamb by domestic consumers and also through developing live

export markets (Hooper et al. 2003; Meat and Livestock Australia 2011a). During this

time the weight of lamb meat exported has more than doubled, driven by growing

demand from United States, Europe, Middle East and Asia (Meat and Livestock

Australia 2004a; Barber and Chou 2009). These increases in demand contribute

positively to the Australian financial performance. For example, in 2009/10 Australia

exported 45% of all lamb worth $932 million (Meat and Livestock Australia 2011a),

compared with $301 million for lamb exports in 1998 (Sheales 1999). Live sheep

exports from Australia are primarily sourced from Western Australia, which accounted

for approximately 82% of the national trade in 2005 (Hassall and Associated Pty Ltd

2006a).

Further, the Australian sheep production system has relied on pasture to turn-off sheep;

however, its growth is unpredictable due to seasonal conditions and climate change.

Approximately 60% of sheep producers rely on pastures to finish lambs, with a further

25% of producers using supplementary feeding and there is also a trend to use fodder

crops to finish lambs, although this practice is not common (Connell et al. 2002). In

Western Australia, annual crops and pastures are grown during the winter months when

rainfall increases, and mature during spring and early summer as temperatures and rates

of evaporation rise and rainfall decreases (Turner 2004). Hence, crop and pasture

growth is usually cut by terminal drought. In Mediterranean environments, such as in

South of Western Australia, plant growth can also be limited by high temperatures

and/or the associated high water deficits (Turner 2004).

Additionally, climate change and in particular periods of drought adversely affects not

just year-to-year productivity and influences the nature of the sheep industry. Since the

mid-1970s, the wheatbelt of Western Australia has experienced a significant decline

(21%) in winter rainfall, which is thought to be caused by a large-scale change in global

climate (Smith et al. 2000). Widespread drought in 2002–03 contributed to a substantial

4

(32%) decline in the sheep population in Australia, as drought has reduced real or

perceived carrying capacity and financial stress on farming businesses (Hooper et al.

2003). Accordingly, there are frequent fluctuations in live lamb exports due to drought

induced supply problems (Hooper et al. 2003; Keniry et al. 2003). The very limited

supply in drought years, combined with buyer competition to secure enough product to

meet demand, has resulted in increase in sheep prices (Athas 2011).

The seasonal distribution of pasture production and its nutritive value varies

significantly throughout the year (Anslow and Green 1967). Thus, this variation in feed

availability induces seasonal restrictions in the feed supply for the animals, which is

commonly called a “feed gap”. The main period of feed deficit in Western Australia

occurs in autumn-early winter when both the quality and quantity available are limited

(Moore et al. 2009), or when the supply of pasture, stubbles and residues are exhausted

(Doole et al. 2009). The seasonal periods of feed deficit usually impact negatively on

the rate of forage intake as well as animal growth (Doole et al. 2009).

Metabolisable energy (ME) is the best (common) unit to measure variations in the

quality of feed (Weiss 1993). The marginal value of feed during the period of feed

scarcity can be used as an “integrative measurement” of the economic importance of

feed shortage (Ewing et al. 1989). As pointed out by Moore et al. (2009, p.737), the

marginal value of feed can be defined as “the rate at which whole-farm profit would

change per unit of extra ME supplied by the pastures on the farm at that time of year”.

This marginal value will vary depending on the type of livestock enterprise and many

other (system) factors, so typically is estimated using whole-farm economic models

(Bell 2008).

Many management approaches have been used to avoid seasonal feed shortages. These

are: strategic options that usually involve a change in lambing time, stocking rate and

selling date, and tactical responses such as grazing cereal crops, destocking and adding

nitrogen fertiliser to grassy pasture (McFarland et al. 2005; Moore et al. 2009).

The use of cereal crops such as wheat, oats and canola for the purpose of both forage

production and grain is an expanding in Australia, particularly in the high rainfall areas

of Australia (Virgona et al. 2006; Kirkegaard et al. 2007), and recently in the drier

5

environments of South and Western Australia (Moore 2009). Grazing of cereal crops

has been shown to significantly increase farm profit by providing high quality green

forage to overcome winter and summer feed shortages without major effects on grain

yield (Kirkegaard et al. 2008). Wheat is the primary cereal grain crop in mixed-farming

systems in the Western Australia Wheatbelt (Ewing et al. 2005). Increased farmer

interest in grazing wheat crops has been revealed in several studies (Moore et al. 2004;

Dove and McMullen 2009; Moore 2009). Interest in this technology also increased

among wheat growers after the 2002 drought, when scientific research concluded that

yields of grazed crops were higher than of grain-only crops (Virgona et al. 2006). In

addition, the interest in grazing wheat has also been motivated by the development of

new dual-purpose wheat varieties bred with a longer period of vegetative growth (e.g.

Triticum aestivum var. and EGA Wedgetail) compared with the common short season

grain oriented spring varieties such as Wyalkatchem and Chara (Ewing et al. 2005;

Virgona et al. 2006; Kirkegaard et al. 2007).

However, grazing of wheat crops requires careful management with regard to the

season, crop species and varieties, crop phenology, the sowing date and grazing

purposes to reduce and avoid grain yields penalties (Kirkegaard et al. 2007). This issue

are particularly applicable to spring wheat variety as they provide short grazing

opportunities due to the time difference between when there is sufficient plant biomass

for grazing and when the crop is too mature to graze without incurring of a significant

penalty in grain yield (Doole, et al. 2009; Moore et al. 2009). To date, much of the

research on grazing crops has focused on the utilization of early sowing dual-purpose

winter wheat varieties grown in high rainfall areas of Australia as they afford longer

grazing opportunities during each season (McMullen and Virgona 2009).

There is a need to investigate the availability of different feedbase components for lamb

production systems, particularly, in autumn/winter feed gaps to identify those with the

potential to reduce lamb production costs and hence increase profitability. We

hypothesized that the integration of wheat crop varieties in lamb production systems

will help mitigate the winter feed gaps and increase farm profit in Western Australia.

This study focuses on grazing two different types of wheat varieties in three diverse

rainfalls areas of Western Australia. These varieties will be referred in the rest of the

paper as “dual-purpose winter wheat” and “spring wheat”. We investigated approaches

6

to reduce winter-feed shortages and increase farm profitability. Furthermore we

attempted to evaluate new management approaches to increase farm business

profitability through reducing supplementary feed costs by providing sheep access to

high quality green feed from immature winter and spring wheat crops. In this paper, the

relevant literature is reviewed followed by a summary of the modeling frameworks used

in our study and their extension to integrate grazed crops of wheat. We then report and

discuss results of model runs investigating profitable farm management in low, medium

and high rainfalls regions of Western Australia. Finally, an analysis of the modeling

assumptions used in this study and their limitations were then presented.

Aims

The aims of this project are to investigate by simulation modeling the profitability of

grazing two wheat varieties (dual-purpose winter wheat and spring wheat) during the

period of feed shortage in Western Australia in a typical lamb production system with

the view to increase productivity and reduced lamb production costs.

Significance and outcomes

The results of this project should be beneficial by helping to provide high quality green

feed during the main feed gap to increase lamb production at a reduced cost and to

ultimately secure high value markets for WA lambs.

7

Chapter One

Review of the literature

Summary

Seasonal feed shortages are one of the major limiting factors in lamb production

systems in Western Australia. Recently, the demand for Western Australian lamb has

increased and is expected to continue to grow. Nonetheless, there is a shortage of lambs

supplied to markets particularly in autumn and early winter due to a scarcity in feed

available either in quality or quantity, or both. Lamb producers have applied many

different strategies to alleviate feed gaps such as pasture conservation, feedlotting,

perennial forage plants, fodder crops and grazing crop stubbles with supplementation to

increase productivity. However, the implementation of these lamb-production practices

is often cost prohibitive. Profitability of the whole farm or lamb enterprise can be

improved by increasing lamb production, minimizing the costs of lamb production

system and reducing the likelihood of feed gaps.

There is a growing interest in grazing grain crops in lamb production systems in

Australia. If managed appropriately, grazing crops can improve livestock productivity

without significantly affecting crop production. The management practice under

investigation in this project is the grazing of dual-purpose winter and spring wheat

varieties in different locations of Western Australia during autumn and early winter in

order to provide green feed, improve lamb productivity to target specific markets and

thus increase the profitability of lamb production system. The study will investigate the

profitability of lamb production enterprises with and without the grazing of immature

dual-purpose and the spring wheat varieties during period of winter feed shortages.

This literature review describes the Australian sheep and lamb industry and the

specifications for the marketing of prime lambs. The review examines lamb production

systems and provides a summary of the nutrient requirements of growing lambs and

how lamb performance is influenced by the quantity and quality of the available

feedbase. Factors that affect the lamb industry are discussed including climatic

conditions and seasonal feed supply deficits as problems within the prime lamb

industry. Also, the review provides an outline of lamb finishing systems and the ways

8

in which seasonal feed deficits can be reduced, with a focus on grazing two different

varieties of wheat to help fill the winter feed gap to increase farm profit.

Australian sheep industry

The Australian sheep industry has historically been dominated by outcomes in wool

markets. However, meat production is becoming an increasingly significant driver of

developments within the industry (Meat and Livestock Australia 2004b). This has been

driven by low wool returns and rising lamb returns, which has led sheep producers to

shift their interest in wool and mutton production towards lamb production (Hassall and

Associates Pty Ltd 2006b). In addition, over the past decade the Australian sheep meat

industry has expanded in response to increasing demand for lamb by domestic and

international consumers through an increased demand for young lamb in the live export

markets (Hooper et al. 2003; Meat and Livestock Australia 2011a).

The Australian lamb industry

The Australian lamb industry is important for both the supply of the domestic market

and its role in generating export income. From 1984-85 to 2007-08, lamb production

increased by 44% (Fletcher et al. 2009). The greater national and international demands

for lamb meat has resulted in the number of lambs slaughtered in Australia increasing

by 30% from 1999-2009, with around 80% of the additional sheep meat produced being

exported, (Fletcher et al. 2009; ABARE 2010).

There are two different types of markets for Australian lambs, the domestic market and

the export market (as carcasses and live exports). Both the size and the structure of

markets for Australian lamb have changed with regard to the proportion of lamb for

domestic and export markets (as meat or live).

In 2002, the domestic market accounted for approximately 68% of Australia’s lamb

production (Hooper et al. 2003). By 2010-11, Australian lamb consumption has

declined to 52% because of increases in retail prices, tight lamb supply and intense

competition from export markets. Nevertheless, with the domestic consumer

expenditure on lamb rising by 80% over the past decade (Meat and Livestock Australia

9

2012a), it is expected that the domestic consumption of Australian lamb will increase by

20% by 2016 (Meat and Livestock Australia 2012a). Similarly, Australian lamb exports

are projected to account for 51% of total lamb, compared with 48.5% in 2011(Meat and

Livestock Australia 2012b)

Live lamb exports from Australia are primarily sourced from Western Australia, with

about two million lambs exported as carcasses each year and further one million lambs

are exported live (Keniry et al. 2003; Meat and Livestock Australia 2011b). Nearly 74%

of total Australian sheep (sheep/lambs slaughtered or exported) destined for the live

export trade are sourced and loaded from Western Australia in 2007-08 (Barber 2009).

The live export industry provides a valuable alternative market for Western Australia’s

sheep producers (Keniry et al. 2003), which has led to a significant improvement in

both Australia’s economy and the financial performance of sheep producers (Meat and

Livestock Australia 2006). In 1998, Australian lamb export volumes were at

approximately AU$301 million in 1998 (Sheales 1999). Ten year later, Australia

exported 45% of all lamb produced worth $932 million (Meat and Livestock Australia

2011a). It has to be noted that over the last 10 years, the value of the export market for

Western Australia lamb producers has fluctuated. Western Australia‘s live sheep

achieved a gross value of $232 million in 2006-07 but only $188 million in 2003-04

(Barber 2009).

Both export markets and domestic markets have increase the demand for Australian

lambs therefore it is important for the Sheep industry to increase productivity and to

raise levels of quality and consistency of supply.

Lamb market specifications

The quality of live and carcass lamb specified by the market is important and there are

strong price signals. Over time, the specifications of different lamb markets have

changed. The lamb markets have become more focussed on purchasing products that

meet their accurate specifications, with demand increasing for larger leaner lambs,

which are mostly preferred by exporters (Hooper et al. 2003; Warn et al. 2006; ACIL

2009). Lambs are exported as long as they have been weaned for at least 14 days before

10

leaving the farm with body weight above 28 kg (Dowling and Wiese 2001; Barber

2009). Recently there has been increase in demand by Middle East countries such as

Jordan, Saudi Arabia and Oman for live younger sheep at 34 kg - 45 kg live weight

range (Hassall and Associates Pty Ltd 2000; Barber 2009).

The live export market demands mostly Merino and fat tailed breeds. However, the

market for slaughter lambs comprised mainly of crossbred lambs (Croker and Watt

2001). In Western Australia, crossbred lambs for slaughter are generally sired by

British breed including Suffolk, Poll Dorset and Border Leicesters (Croker and Watt

2001). Crossbred lambs grow faster than Merino lambs (up to 100 g/day), and they

require less feed to reach target weights (Dowling and Wiese 2001).

Furthermore, the lamb sale prices depend on how individual animals meet the

specification requirements such as for weight and fat cover; accordingly if a lamb fall

outsides these specifications, the price is decreased (Croker and Watt 2001; Barber and

Chou 2009). Returns from sales of lambs at market will also depend on the timing of

sales. For instance, sucker lambs being sold in spring tend to return lower price

compared with earlier sucker lambs in June, July and August (Dowling and Wiese

2001). These approaches provide feedbacks to producers and drive them to modify

their production systems to meet buyers’ requirements.

Lamb production systems

In Western Australia, lamb production systems require a consistent supply of high

quality feed to meet the lamb’s nutrient requirements in order to finish them quickly for

markets. Lamb production systems are influenced negatively by the variations in feed

supply in particular the quantity and quality of the feedbase. These variations have led

many producers to change their management practices, in particular matching the time

of lambing to the patterns of pasture production (Croker et al. 2009).

Joining and lambing time

Time of joining and consequently lambing is an important management decission in a

lamb production system, which interacts with the availability of high quality feed in

determining lamb performance. In most regions of Western Australia, ewes (mainly

11

Merino) are joined with a British breed (e.g. Poll Dorset) ram (Griffith et al. 1995).

Lambing times of ewes is typically in early winter from April to July, and lambs are

finished from August to December (Croker et al. 2009). This means that in many

seasons peak lambing occurs when Western Australia pastures are unable to meet the

feed requirements of ewes and lambs (Croker et al. 2009).

In Western Australia, some prime lamb producers join merino ewes to terminal sires for

early lambing (mid-April) to achieve a premium price in the early sucker lamb market,

however ewes require more feed in autumn where feed supply is limited (Milton et al.

2001). Nonetheless, finishing coincides with peak pasture growth in spring (Hanrahan

1994). The nutrient requirements of lactating ewes are much higher compared with dry

ewes. For example, lactating ewes require at least double their normal energy intake to

produce sufficient milk for their lambs (Milton et al. 2001; McFarland et al. 2005).

Further, the lower birth weights and growth rates of the autumn lambs are probably due

to not meeting the nutritional requirements of ewes in late pregnancy and early lactation

(McClymont and Lambourne 1958; Taplin and Everitt 1964; Mullany 1966). Therefore,

lamb growers should take into consideration the fluctuations in nutritional requirements

for both ewes and lambs when choosing the optimum mating and lambing date to

improve lamb productivity.

Lamb nutrient requirements

Meeting the nutritional requirements of lambs during the period of peak production is

one of the producer's biggest challenges. There is wide variation in the literature on the

nutrient requirements of the fast growing lamb (Jolly and Wallace 2007). The major

categories of nutrients required by lambs are energy, protein, vitamins, minerals and

water (Milton et al. 2001; McDonald et al. 2002; Freer et al. 2007). The growth rates of

young sheep during winter and spring should be in the proximity of 214 to 286

g/head/day once there is a sufficient green feed available (Devenish et al. 2001).

However, the growth of lambs is often low at the start of the growing season

(particularly during June and July period) as there is usually a limited supply of green

feed. Consequently, feed shortages will affect the profitability of livestock enterprises

by reducing the animal’s productivity over the year (Moore et al. 2009).

12

The nutrient intake by a lamb is closely related to both dry matter (DM) and nutritive

value of the feedbase expressed as mega-joules per kilogram dry matter (MJ ME/kg

DM) (Kerr 2000; Milton et al. 2001; Oddy et al. 2002). Commonly, Merino lambs

require a ration containing about 10.5-11.0 MJ/ME/kg/ of DM and 14-16% crude

protein, to achieve a sufficient energy intake to meet their growth potential (Nugent and

Milton 2004). Daily DM intake of fast growing lambs can vary between 3.8-4.2% of

their live weight (NRC 1985). For example, a 30 kg lamb growing at 200 g/day will

consume around 1.3 kg DM intake per day of high quality diet (Jolly and Wallace 2007;

Burnett and Ponnampalam 2011). However, many factors affect DM intake including

digestibility of the ration, forage preference, rumen outflow rate, protein and water

content of the feed, the pH level of the rumen fluid, the rate at which feed is degraded

and the weight and age of lambs (Milne 1991; Manso et al. 1998; Phy and Provenza

1998).

The energy content of a forage affects lamb performance more than other nutrients

(Michalk and Saville 1979). For instance, in growing animals, an early sign of energy

deficiency is reduced growth, then weight loss, and ultimately death (Milton 2001;

McDonald et al. 2002). Lambs must consume an adequate amount of nutrients to meet

their maintenance requirements with any remaining nutrients available for growth

(Oddy et al. 2002). Clearly, when nutrient intake is close to maintenance, lambs will

take a long time to reach the desired market weight and only a small proportion of the

overall intake is available for growth. Conversely, lambs will reach market weight

quicker, and will use a higher proportion of their energy intake for growth, when they

are fed high quality feed due to a higher rate of nutrient intake and higher

growth:maintenance ratio for energy partitioning (Milton et al. 2001).

In small ruminants such as lambs, the amount of protein is more important than the

quality of the protein (McDonald et al. 2002). Microbial protein by itself is often

adequate to support respectable growth rates. The microbes in the rumen are able to

produce protein from non-protein nitrogen as well as from the protein in their diet

(Ramirez 1999; McDonald et al. 2002). Green pastures provide sufficient protein,

however, the quantity of protein in pastures is less as the pasture mature, especially after

the vegetative growth (Devenish et al. 2001). For example, the concentration of protein

decreased by 30% between the vegetative and reproductive stages, and by 10% between

the reproductive and senesced stage of growth (Thomas et al. 2010). The microbial

13

population in the rumen decreases when the protein intake is insufficient, therefore

fewer microbes will be available to break down the structural carbohydrates that enter

the rumen, and consequently, the feed intake and growth rate of the lambs will reduce

(Devenish et al. 2001; McDonald et al. 2002).

While energy and protein are the key nutrients that limit animal growth particularly in

fast growing animals, certain minerals and vitamins can also limit growth if they

become deficit. There is also a need for macro-minerals including calcium, chlorine,

magnesium, phosphorus, potassium, sulphur and sodium in relatively large amounts

(e.g. grams per kilogram) (Masters et al. 1993; Norman and Masters 2010).

Deficiencies in trace minerals such as copper, selenium and vitamins (cobalt B12) will

occur if pastures have not been fertilized with suitable trace fundamentals or

supplements are not provided, which will result in reduced lamb growth (Masters et al.

1993; Havilah et al. 2005; Norman and Masters 2010). In Western Australia, trace

minerals are most likely to be deficient during seasonal feed scarcities, and thus may

affect lamb health and growth (Milton et al. 2001). Additionally, feeds with an

unbalanced mineral profile (such as the high salt content of saltbushes) may have

reduced digestibility and intake and thus affect live weight gain in sheep consuming

these feeds (Thomas et al. 2007).

Further, young sheep that have experienced several months without green feed are

likely to experience vitamin deficiencies including vitamins A, E and K and vice versa

(Croker and Watt 2001). Vitamin D is synthesised in the skin provided animals are

exposed to enough sunlight (Milton et al. 2001). In addition, Milton et al. (2001, p.18)

reported, “feed produced in high rainfall environments tend to have lower levels of

vitamins and minerals because their concentrations are diluted in the fast growing

plants”. Indeed, supplying the nutrients requirements for both ewes and their lambs and

supplying them with consistent high quality feed sources during the production cycles

are important to obtain high levels of animals performance.

Feedbase in lamb production systems

While lamb production systems require a consistent supply of high quality feed, the

wide variety of feed sources that are used (feedbase) and the seasonal variation of

14

forage production in Western Australia means that the quality and quantity of the

feedbase fluctuates during the production cycle (McFarland et al. 2005). This often

leads to nutritional inadequacy with insufficient energy for maintenance rations and

protein deficiencies (Moore et al. 2009).

Lamb production systems typically rely on several sources of feed such as pasture,

forage crops, conserved forage, perennial plants (e.g. Lucerne, Medicago staiva L.),

grains (e.g. lupin) and crop stubbles (Moore et al. 2009). Jolly and Wallace (2007)

consider that, in general, metabolisable energy (ME) content is a common unit that can

be used either to measure both quality among feed sources, or to compare the nutrient

supply of pasture and the total nutrient demand for different production enterprises

(Weiss 1993; Moore et al. 2009).

Feedbase quantity

Although, there are many different components available to the grazing animal, the

quantity (such as biomass, height, density and the seasonal availability) of those feeds

may not be sufficient to supply the requirements of lambs during the peak of production

periods. The quantity of feed in a paddock is assessed by estimating the dry weight of

all above ground plant material (plant biomass; Croker and Watt 2001), and it is

estimated in kilograms of dry matter per hectare (kg DM/ha). Generally, this method is

called Feed on Offer (FOO) or Herbage Mass (HM) (Devenish et al. 2001).

Furthermore, the quantity of herbage availabledepends on the plant genotype, the

maturity of vegetation, seasonal rainfall and its distribution, environmental temperature,

soil type and fertility, disease and grazing intensity (Norman and Masters 2010). For

example, lucerne pastures are capable of producing levels of total biomass

approximately comparable with subterranean clover over a year, but the lucerne plant

material is, on average, higher feeding value because it is a perennial plant and can

grow during summer and autumn (Croker and Watt 2001).

In Western Australia, livestock feed is traditionally most scarce during late summer to

the autumn and usually extends into early winter (Fig. 1), when supplies of stubbles and

residues are exhausted (Doole, et al. 2009; Moore et al. 2009). The slow growth of

15

pastures during winter (e.g. June and July) can be attributed to low levels of light, a low

leaf area index and frosts (Devenish et al. 2001). As a result, lamb production is

negatively influenced by the restricted pasture supply during this period.

Feedbase quality

The nutritive value and feeding value of feed source are useful measures of the quality

of forage and need to be high for high levels of animal performance (Dynes et al. 2003).

The metabolisable energy of the pasture available is highly variable and can range from

5.7 to 12 MJ ME/kg DM depending on its botanical composition (e.g. proportion of

grass and legume), its stage of growth and the time of year and morphology (e.g. leaf,

stem, or dead) composition (Ulyatt 1981; Kerr 2000; Thomas et al. 2010).

For instance, the energy content of ryegrass decreased by 6% between the vegetative

and the reproductive stage compared with 21% between the reproductive and senesced

stages of plant maturity (Thomas et al. 2010). Summer pasture has lower ME content

compared with those grown in winter, and the ME of leaf and stem declines at high

temperature (Kerr 2000).

Fig. 1. Typical feed gaps in two regions in Western Australia highlighted by the shaded areas.

Long term average monthly ME (MJ/ha/day) supply from pasture (line with black circle) and

16

the demand (line with white circle) for ME by a typical beef cattle breeding enterprise (Moore

et al. 2009).

The quality of herbage is influenced by a range of factors including concentration of

energy and protein, minerals and trace elements (Ulyatt 1981). Norman and Masters

(2010) indicated that live weight of sheep increased when the pasture or forage have a

dry matter digestibility (DMD) of about 70% (see Fig. 2). Additionally, the digestibility

of young green feed in spring and winter is higher (70%-80%) than mature pastures

(below 45-60%), therefore many forage-based systems are not suitable for finishing

lambs without supplementary feeding (Milton et al. 2001). The digestibility of pastures

is often high during the growing season (winter and spring period), yet this digestibility

declines rapidly as pastures mature and senesce (Thomas et al. 2010). During this

period even non-lactating adult sheep may not be able to maintain their weight or meet

their required energy intake on dry pastures (Devenish et al. 2001).

Improved production is obtained if lambs are given access to a diet containing more

digestible energy and protein than in mature pasture such as a forage crop, high protein

rations (Kenny and Reed 1984), lupin stubble (Arnold et al. 1975), high quality hay and

perennial pasture (Kenny 1984). Clearly, lamb performance is very sensitive to

fluctuations in the quantity and the quality of their feed, which in turn influences the

consistency of lambs supplied that meet market specifications.

17

Fig. 2. The relationship between DMD and live weight change of ewe (Norman and Masters

2010)

Factors affecting the lamb industry

There are a range of factors that contribute to the consistency of lamb supplied to

markets and thus affect the prime lamb industry in Western Australia. These include

climatic conditions, drought, feed shortage and fluctuations in lamb price.

Climatic conditions

Western Australia has a Mediterranean-type climate with wet, cool winters (from June

to August) and a hot, dry summers/autumn period (from December to late March) (Hill

et al. 2005). Moreover, in regions with a Mediterranean environment, rainfall is the

major limitation to plant productivity (Fischer and Turner 1978). Rainfall increases in

autumn from March to May and reaches a peak in mid-winter and decreases rapidly

during spring (Turner 2004). The high rainfall zones (HRZ) in Western Australia are

where the annual rainfall is between 450 and 800 mm, with a pasture growing season of

7–10 months (Zhang et al. 2006). The annual rainfall of the low and medium areas in

Western Australia is between 300 and 450 mm, where wheat and other crops are

generally grown (Anderson and Garlinge 2000).

18

Further, while the winters are wet and rainfall usually adequate in the Mediterranean

climate zones, cool temperature and frost often limit plant growth in this season (Turner

2004; Hill et al. 2005). Annual crops and pastures mainly grow from late autumn to

spring (Zhang et al. 2006). The potential yield of grain crops is higher in HRZ due to

longer seasons than that in low rainfall zones, and the yield potential of dual-purpose

winter wheat can be much higher than that of spring wheat (Zhang et al. 2006). In the

HRZ of Western Australia, the higher yields, reliable rainfall, and longer growing

seasons lead to higher the returns per hectare (Nix 1975; Doole et al. 2009).

The differences in feed on offer both green and dry in three rainfall zones in Western

Australia are displayed in Fig. 3. Since the mid-1970s, the wheatbelt of Western

Australia has experienced a significant decline (21%) in winter rainfall, which is

thought to be caused by a large-scale change in global climate (Smith et al. 2000).

Consequently, many locations in Western Australian have been challenged with more

frequent and widespread droughts as a result of this decline in average rainfall.

Fig. 3. Green and dry feed on offer in three rainfall zones in Western Australia (Milton et al.

2001).

Drought

There is also recognition in the prime lamb industry of the need to increase productivity

and to raise levels of quality and stability of lamb supply during periods of drought

(Hooper et al. 2003). Major droughts have occurred many times in the past century in

19

many regions of Western Australia particularly in 1982-83 and 2002-2003, which have

had a serious impact on the livestock industries, plant production and environmental

impacts including the loss of ground cover resulting in soil degradation (IPCC 2007).

Western Australia (mainly the Southwest) also experienced very dry conditions during

2010 (Fig. 4), with much below average rainfall 357 mm in 2010 compared with 446

mm in 2001 for the Jan-Oct period in both the winter and autumn seasons (Western

Australia Climate Services Centre 2010).

Fig. 4. The five lowest rainfalls on record in Southwest Western Australia: Bureau of

Meteorology, Western Australia Climate Services Centre 2010.

A significant impact of drought is the frequent fluctuations in the supply of lamb for

exports markets (Hooper et al. 2003; Keniry et al. 2003). One example is that, over the

last decade, lamb exports increased threefold to over 124900 tonnes (carcass weight) in

2001, but drought reduced exports by 12% in 2002 (Hooper et al. 2003), due to the

lower lambing percentages and decline sheep flock. Hooper et al. (2003) reported that

drought in 2002–03 contributed to a substantial (32%) decline in the sheep population

of Australia.

20

Feed shortages

Variation in seasonal conditions and feed gaps can have direct and indirect effects on a

lamb production system. Feed shortages directly affect on livestock production by

reducing the rate of forage intake and influencing animal performance (Moore et al.

2009). For instance, short-term changes in nutrition can directly influence sperm

production, ovulation rate, embryo survival, colostrum production (Martin et al. 2004),

lamb growth rate, wool growth and quality (Thompson and Hynd 1998; Brown et al.

2002).

Further, the feed shortages in drought seasons can have indirect effects on lamb

production, which is likely to increase the number of consignments and the distance

sheep move (Croker and Watt 2001; Hassall and Associates Pty Ltd 2006a). In 2005/06,

the proportion of lamb movement from Western Australia to South Australia was up by

250% (from 100,000 to 250,000) due to a strong seasonal differential and spare abattoir

processing capacity in South Australia (Hassall and Associates Pty Ltd 2006b). During

the 2010 drought, the sheep movement from Western Australia to eastern states

primarily South Australia, Victoria and New South Wales reached around one million

sheep (Easta and Foreman 2011). Finally, the severity of the annual feed gap can have a

marked impact on the profitability of sheep enterprises due to increases in costs for

supplementary feeding. (Moore et al. 2009).

Fluctuations in lamb price

A lambs’ sale price depend on how the animal meets the specified market requirements,

particulary for weight and fat cover and if a lamb carcase falls outside these

specifications the price is decreased (Croker and Watt 2001; Barber and Chou 2009).

The decision to sell into higher carcase weight markets means that a wether lamb may

need to be at approximately 14 months of age and the sale price per kg could fall by as

much as $1.00 per kg if the wether is no longer classified as lamb when slaughtered.

(ACIL 2009).

In addition, the returns from the sales of lambs depend on the timing of sales. For

example sucker lambs being sold in spring tend to return a lower price compared with

earlier sucker lambs in June, July and August (Dowling and Wiese 2001). Peak prices

21

for lambs in Western Australia are generally received around the April-July period

when there is a supply shortage (Connell et al. 2002). For producers to supply the

market at this time of the year means that lambing needs to start in summer and early

autumn when there is a lack of pasture availability (Croker and Watt 2001; Connell et

al. 2002). Furthermore, to achieve premium market prices, many lamb producers try to

finish lambs ‘out of season’ from December to August (Croker and Watt 2001), when

green feed is often limited especially in the months of May to July.

Lamb finishing systems

A lamb finishing system is defined as a feeding system that aim to meet the specific

protein and energy requirements for optimum daily live weight gain, and also refers to

the period between weaning and reaching a marketable slaughtered weight (40-50 kg

live weight) for domestic or export markets (Burnett and Ponnampalam 2011). The

lambs are usually sold after weaning at three months of age, at around 38 kg live weight

(17 kg carcase weight) and condition score 3 or 4 (Griffith et al. 1995; ACIL 2009).

Prime lamb producers usually have two different options for marketing their lambs.

Firstly, sucker lambs that have not been weaned from their mothers before sale, and

they usually need to maintain a growth rate above 250 g/head/d to reach their minimum

target slaughter weight of 40 kg before the green feed dries off (Croker and Watt 2001).

Secondly, carryover lambs are those that are weaned from their mothers and grown out

to meet various market requirements (Croker and Watt 2001; Milton 2001), and they are

usually sold outside the spring flush of lambs. Intensive finishing of lambs can be a

high-risk enterprise, with high turnover and low margins (Goers and Jolly 2007).

Therefore, the factors that drive profit in the system need to be considered carefully in

order to implement strategies to diminish risk within these areas. The following section

will outline these factors.

Economics of lamb production

Careful management of lamb production systems in relation to feedbase and seasonal

outcomes will drive the profitability of lamb production systems. The efficiency at

which lambs convert feed to live weight gain versus a range of costs include livestock

22

health and processing, pasture establishment and maintenance and feed conservation

costs further influence profitability (Griffith et al. 1995; Norman and Masters 2010).

Feed is a major cost of lamb finishing systems (Milton 2001). For example, feed costs

in feedlot system an account for around 60% of the total costs of finishing lambs (Jolly

and Wallace 2007).

Further, if the expenses incurred to finish lambs exceed the price margin, the system

will be unprofitable. The price margin is defined as the difference between the price of

purchasing lambs that enter the finishing system and the sale price of finished lambs to

target markets (Goers and Jolly 2007).

The length of time that a lamb spends on feed to get to the target market weight can

impact significantly on the profitability of mixed farming systems, primarily during

periods of feed deficiency (Norman and Masters 2010). Finishing lambs in summer or

early autumn/winter is costly due to the shortage of green feed in these seasons; but this

varies depending on which finishing system is used (Croker and Watt 2001). So, getting

an appropriate feeding system during these periods of feed shortage to finish lambs is

important for optimising lamb growth rates and the potential return to the producer.

Management strategies to overcome a feed deficit

There are many ways to alter the feed supply to alleviate feed gaps: These include

strategic responses, tactical responses and by increasing the supply of forages including

perennial pasture based systems, feedlotting and fodder crops (Moore et al. 2009).

Nevertheless, all these systems have their limiting factors and the implementation of a

particular lamb finishing system is often cost prohibitive.

To overcome the periods of extended feed scarcity, “growers tend to adopt low-input

agronomic strategies that result in low returns per hectare, but reduce risk” (Moore et al.

2009). Strategic options include changing stocking rate, shearing time, mating and

lambing time and selling stock (Moore et al. 2009). Another option is ‘tactical

agistment’ such as adjustments to nitrogen application to grassy pasture, grazing a

cereal crop, changing enterprise selection and destocking practices (Moore et al. 2009).

Nitrogen fertiliser can be applied to crops or pasture with earlier sowing to boost growth

and to lift the protein level in feed consumed by livestock (Doole et al. 2009). Tactical

23

responses have the potential to make substantial improvements in expected returns

(Kingwell et al. 1993).

Additionally, lambs producers tend to use different feeding management practices to

decrease feed gaps. The first, perennial pasture finishing systems which typically

include the use of species such as lucerne, chicory, phalaris, perennial ryegrass and

native grasses that are summer active (Croker and Watt 2001). Perennial pastures have

some growth activity throughout the year and this is especially important in summer

when annual pastures are not growing (Moore et al. 2006). However, the production of

summer and autumn perennial pasture such as lucerne and chicory in Mediterranean

environments (such as Northern and Avon regions in Western Australia) can be risky

due to the extremely variable rainfall (Moore et al. 2009).

Moreover, feedlotting has been used widely as an alternative option for production

feeding during a seasonal drought and/or during the period of feed deficit, to bring

unfinished lambs up to market specifications (Milton et al. 2001). While feedlotting

gives producers the flexibility to finish lambs irrespective of seasonal conditions, other

options may be more profitable, and should be considered (Goers and Jolly 2007). As

well, grain finishing involves financial risk; in particular lamb deaths, shy feeders,

unexpected changes in market prices for lambs and grain, the costs associated with

labour, feeder equipment, health, shearing and transport (Milton et al. 2001; Jolly and

Wallace 2007).

In addition, forage crops, such as oats (Bell 2008) and sorghum (Roberston et al. 2005),

can be of significant value by providing winter forage in parts of Western Australia.

However, growing summer crops (e.g. sorghum) may be risky and is rarely economic

(Robertson et al. 2005). This type of intervention relies on availability of either rainfall

or stored soil water to grow the forage crops (Moore et al. 2009). Further, Moore et al.

(2009) showed that forage shrubs can play a valuable role in alleviating feed gap due to

their capacity to tolerate extended dry and hot conditions over summer and provide

green feed in autumn. Recently, there has been growing interest in the integration of

dual-purpose cereal crops in mixed farming regions in Australia (Virgona et al. 2006;

Kirkegaard et al. 2007) and particularly in drier environments of South and Western

Australia (Moore 2009).

24

Grazing cereal crops

Dual-purpose (DP) cereals are defined as crops that are sown to provide green forage to

fill winter feed gaps as well as for grain production (McCormick et al. 2011). The use

of cereal crops such as wheat, oats and canola for the purpose of both forage production

and grain is an expanding technology in Australia. This practice can provide extra

income by providing high quality forage and grazing opportunities to help overcome the

winter and summer feed gaps without major effects on crops yield (Kirkegaard et al.

2008). Virgona et al. (2006) reported that interest in dual-purpose crop varieties

increased further among wheat growers after the 2002 drought when there were reports

of higher yields of grazed crops compared to crops that produced only grain.

Likewise, the interest in grazing wheat crops practice is motivated by the development

of new wheat cultivars bred with longer period of vegetative growth include Triticum

aestivum var. and Enterprise Grains Australia (EGA) Wedgetail, compared with the

widespread short season grain oriented varieties such as spring varieties Wyalkatchem

and Chara (Ewing et al. 2005; Virgona et al. 2006; Kirkegaard et al. 2007).

Grazing wheat crops

Wheat crops are the primary enterprise in many mixed-farming systems in the

Wheatbelt of Western Australia (Ewing et al. 2005). Wheat crops are mainly grown to

harvest for grain in Western Australia and stubbles, hay, and grazed crops are also used

as a source of feed for sheep (Doole et al. 2009). When compared to spring wheat

cultivars, dual-purpose winter wheat is slow maturing and so has a relatively long

period for grazing before initiating reproductive growth (Moore 2009).

Also, dual-purpose winter wheat can be sown early (March to April), as they remain

vegetative during the coldest time of the year when there is a risk of frost damage

(which usually occurs in late winter), and they are able to recover from grazing to

produce grain (Virgona et al. 2006). Dual-purpose winter wheat varieties suit areas with

a long growing season and usually an early and reliable autumn break (Doole et al.

2009). Moore et al. (2009) indicated that spring wheat cultivars provides a short period

for grazing in the drier parts of Western Australia when the shoot mass was 1000 kg/ha,

25

however, to increase the grazing period of spring wheat cultivar, the shoot mass has to

be below this amount to avoid the removal of reproductive meristems.

Advantages of grazing wheat crops

Grazing wheat crops is a valuable resource and an attractive management option to

farmers for several reasons:

First, grazing wheat crops have value in filling seasonal feed gaps (Kelman and Dove

2009). Additionally, Moore (2009) found that grazing wheat cultivars could provide a

winter-feed resource particularly during the May-July period, when growth of pastures

is generally less than livestock requirements. Furthermore, growth rates from early

sown dual-purpose winter wheat can be as great as 100 kg/ha/DM/day in mid/late

autumn and average growth 30–60 kg/ha/DM/day through to the end of grazing. In

contrast, pastures at that time of the year often grow at 5–10 kg/ha/DM/day and even as

low as 1.0 kg/ha/day in colder areas, while growth rates from late sowings (e.g. late

autumn) are usually 10–20 kg/ha/DM/day, and even as low as 1.0 kg/ha/day in colder

areas (Freebairn 2005). The slow growth of pastures during winter (e.g. June and July)

can be attributed to low levels of light, a low leaf area index, plant genotype and frosts

(Devenish et al. 2001).

Second, grazing of wheat crops in productive environments can reduce stubble load and

simplify ease of sowing in the subsequent season (Baumhardt et al. 2009; Harrison et

al. 2011). Third, both experimental and modelling studies have shown that grazing

wheat crops are more profitable than grain-crops as a result of generating income from

both livestock and crop resources which in the long term alleviates risk (Moore 2009).

However, the profitability from grazing wheat crops could be different in Western

Australia since the climatic conditions are generally different to the Eastern states where

most of the previous studies have been conducted.

Yields of the spring wheat cultivar (Yitpi) were generally greater than those of the

corresponding dual-purpose winter type such as EGA Wedgetail in Western Australia

environment (Miyan and Clune 2008). Similarly, Moore (2009) pointed out that the

grain yield of dual-purpose winter wheat cultivars were lower than those of spring

26

varieties in Western Australia. Moore (2009, p.766) explained “the main limitation to

yield of dual-purpose cultivars in Western Australia regions is a combination of warmer

winter temperatures slowing vernalisation with earlier terminal drought, which together

shorten the grain-filling period of the dual-purpose cultivar and prevent it from

expressing its higher yield potential”.

Finally, the forage from grazing wheat crops is of high digestibility and crude protein

content, and is thus conducive to high livestock production (Dove et al. 2002; Dove and

McMullen 2009). For example, wheat crop has in vitro mean DM digestibility of 80%,

a mean crude protein content of 22.4% and energy content of 12 MJ ME/kg DM

(Milton et al. 2001; Doole et al. 2009). The expected live weight gains of young sheep

grazing early sown wheat are 200-300 g/d (Kirkegaard et al. 2008; Burnett and

Ponnampalam 2011).

Management of animal grazing on wheat crops

Grazing can have a negative impact on cereal crop production depending on the timing

and duration of defoliation, seasonal conditions, and the impact of grazing on the water

use efficiency of the crop (Ewing et al. 2005; Virgona et al. 2006). Given that grazing

intensity and grazing duration influence wheat grain yield, it is important to indicate

that grazing animals should be removed before wheat reached Zadok’s growth stage 31

(Kirkegaard et al. 2008). Livestock grazing dual-purpose winter wheat might face

deficiencies in sodium, however, this deficit can be simply and economically resolved

resulting in sharp increases in the frequency and consistency of animal production from

grazed wheat crops (Dove and McMullen 2009; Moore et al. 2009).

Farm system simulation modelling

Farm system modelling provides a reasonable way of representing relationships in

grazing systems so that complex interactions (interactions between pastures, animals

and the environment) and their effects on each other can be quantitatively assessed

(Finlayson et al. 1995). Over the last decade, there has been an increase in the use of

models in research programs, both independently and in combination with experimental

27

work (Moore 2009). Recently, a modelling study by Doole et al. (2009) indicated that

grazing wheat crops may provide a valuable source of feed in high rainfall zones in

Western Australia which can partially fill winter feed gap, and allow annual pastures to

establish more vigorously thereby increasing farm profitability. Therefore, there is an

opportunity to investigate the possibility of using dual-purpose winter wheat and spring

wheat cultivar in lamb production systems during the winter feed gap and evaluate lamb

productivity, production costs and enterprise profitability when using these crops.

Conclusion

Feed gaps impact significantly on improving sheep productivity and thus reduce farms

profitability. It is clear that meeting demands for both domestic lamb and live exports

markets during the period of winter feed shortage is difficult, expensive and may

involve some interacting complexities. This literature review has addressed some

approaches to alleviate these feed gaps. Overall, previous studies suggest there may

well be scope for using winter and spring wheat cultivar to partially fill the winter feed

gap with green feed and reduce the need for supplementary feeding while also

minimizing pressure on the pasture feedbase. Further, grazing wheat crops might have

the potential to finish lambs quickly to market by supplying high quality green feed

during feed scarcity.

28

Chapter Two

Materials and Methods

A simulation experiment was conducted using the GrassGro biophysical model (version

3.2.0) and the Agricultural Production Systems Simulator (APSIM version 7.3) to

investigate the effect of grazing winter and spring wheat cultivars on the profitability of

Merino ewe enterprise at three sites in Western Australia. In order to cover the range of

annual rainfalls in Western Australia, simulations were carried out for three regions,

representing the high rainfall (Kojonup), the medium rainfall (Wickepin) and the low

rainfall zones (Merredin) of Western Australia’s grain growing region (Table 1).

The GrassGro simulation model developed by CSIRO is a pasture grazing systems

model (Donnelly et al. 1997; http://www.grazplan.csiro.au, verified 29 March 2012).

GrassGro integrates soil characteristics (e.g. soil water holding capacity) and historical

daily climate data (rainfall, maximum and minimum temperature, potential

evapotranspiration and solar radiation) for the chosen time interval (years) within the

specific site and allows for the requirement of pasture species combinations to be

simulated over time (Alford et al. 2006). A number of components in the GrassGro

model were used to describe each portion of the biophysical (climate, soils and farm

management (paddocks) pasture, livestock), managerial (such as stocking rate, soil

fertility, pasture grazing rotation and reproductive management), and economic values

within the farm system under consideration (Mokany et al. 2010). This model generates

data outputs using reporting templates that can be modified. However, wheat crops are

not available in the GrassGro plant component.

Therefore, a simplified crop and Merino ewe enterprise was also simulated using the

APSIM model (using a comparable genotype and stocking rate). APSIM’s modelling

capability is primarily developed for cropping systems, with crop modules available for

the majority of the grain and fiber crops such as wheat, which grown in temperate and

tropical areas (Keating et al. 2003). The objective function of the APSIM model in this

study was to obtain the standing biomass parameters for both winter and spring wheat

crops, present at each day between sowing and harvesting, by running a series of

simulation experiments for the three study sites. Accordingly, from APSIM and

29

GrassGro data outputs, summaries are generated using Microsoft Excel 2010 to

calculate the profitability of the farm enterprise and crop grazing days at each site for

the chosen period (50 years). Each of these models have been applied and published

widely in the analysis of a variety of agricultural problems (Moore et al. 1997;

Donnelly et al. 2002; Keating et al. 2003; Robertson et al. 2009).

Weather and soil

Historical weather data for the three sites of Western Australia were obtained in each

model as Patched Point datasets from the SILO database

(http://www.longpaddock.qld.gov.au/silo, verified 21 March 2012). Simulations were

run from 1958 to 2009; only the 50 years from 1960 to 2009 were included in the

analysis of results, in order to prevent the initial setup conditions affecting the

outcomes. The average annual rainfalls during this period were numerically different for

Kojonup, Wickepin and Merredin respectively (Table 1). Soil in the APSIM model was

a deep sand soil (Buntine No 146; Australian Soil Resource Information System 2006).

For the GrassGro simulations, however, paddocks were assigned sandy soil type

(Binnu-Uc5.22) supporting five different soil fertility scalars (0.7, 0.75, 0.8, 0.85 and

0.9) as described by Mokany et al. 2010. In order to create paddock replication within

the three Western Australia’s regions, we used similar components for each paddock but

with differing soil fertility. Each year, soil water was not reset, so that soil water at

sowing in each year reflected the previous year’s water balance and plant productivity.

Table 1. Western Australian locations (high, medium and low rainfall) used in the

grazing wheat crop simulation modelling study

Site Latitude Longitude Mean annual rainfall*(mm)

Kojonup 33º50'S 117º09'E 528

Wickepin 32º80'S 117º50'E 403

Merredin 31º29'S 118º17'E 319

*Rainfalls data were averaged over 1960-2009.

30

Stocking rate

In this study, farm stocking rate or potential carrying capacity in Dry Sheep Equivalent

(DSE) was determined according to the total annual rainfall for each site, using the

equation developed by French (1987):

Potential stocking rate (DSE/ha) = [(Annual rainfall mm - 250) x 1.3] /25 (1)

French indicated that potential stocking rates for a property increased by 0.7 - 1.3

DSE/ha for every 25 mm rainfall in excess of 250 mm (French 1987). In this study,

however, a value of 1.14 DSE/ha for every 25 mm over a 250 mm rainfall was used

instead according to the top 20% farms in Southwest Western Australia in 2010-11

(DPI 2011). In all simulations, the value of one DSE corresponds to a wether in average

body condition score at a weight of 50 kg. DSE grazing days was calculated according

to Standing Committee on Agriculture (1990):

DSE grazing days = FEin / 8.8 MJ ME (2)

Where:

FEin is total flock ewes metabolisable energy (ME) intake (MJ ME/ha/day)

8.8 is the ME required for maintenance of 50 kg Merino wether of medium breed size

consuming a diet of 10 MJ ME/kg DM (Standing Committee on Agriculture 1990).

GrassGro model

Model farm and pasture management

This simulation model was based on a Merino ewe enterprise grazing an annual

ryegrass (Lolium rigidum Gaud.) and subterranean clover (Trifolium subterraneum L.)

pasture at three locations in Western Australia (Appendix 1). The biophysical model

farm comprised a 700-ha paddocks assigned for annual pasture and two 1-ha feedlot

paddocks (one to grow lambs to market specifications and other for ewe maintenance

feeding as required). Given that the wheat crop cannot be grazed in GrassGro model,

this was substituted with a ‘lucerne pellets’ supplement to create a grazing wheat

31

parameter in the GrassGro plant component, which had a metabolisable energy

concentration of 12.3 ME MJ/kg reflecting the wheat crops’ ME. The farming system

was replicated 5 times; one of five soil fertilities rates. Annual pastures grazing events

occurred when the total green herbage biomass was exceeding 800 kg/ha at each

location.

Livestock management

The stimulated paddocks supported a Merino ewe enterprise producing crossbred lambs

(Poll Dorset × Merino). The weight of a mature ewe in average condition was set at 50

kg. Ewes aged 1-2 years were mated to Dorset rams (breed standard reference weight 60

kg) on 4 October each year at rate 50 ewes for one ram. First-cross ewe replacements

for this system were purchased on 1 December aged 18 months and weighted 45 kg

with condition score of 2.5. Mature ewes were sold on 29 November when they reached

age 5 years and 8 months. The shearing date for ewes was 20 November each year and

weaners were shorn on 29 September. Lambing occurred on 1 March and lambs were

weaned on 20 May each year and could graze the wheat crops from this time. All male

weaners were castrated. In the simulation study, young sheep (ewes and wethers) were

sold either on 7 July at age 18 weeks or at a target weight of 45 kg as finished lambs by

1 October. The ewe-stocking rates were 8.5 at Kojonup, 4.6 at Wickepin and 2.1

animals/pasture ha at Merredin.

Ewes were fed a grain ration consisting of 20% lupins and 80% barley in feedlot

paddocks to maintain their body condition whenever their condition score fell below 2.

Young stock were fed the same ration but in a feedlot to maintain their body condition

score above 1.5. Flock ewes were supplemented with lucerne pellets ad libitum in a

feedlot from 1 April to 1 August when the total pasture green dry matter fell below 800

kg/ha, and ended when green herbage DM biomass exceeded this amount. Weaners

were fed a grain supplement in a feedlot from 1 August to 1 October at a feeding rate

set so the lambs would reach a market target weight of 45 kg by 1 October. Additional

details on the commodity prices used in the analysis are given in Table 2.

32

Table 2. Meat, wool and grain prices and other costs used in the analysis

* based on the value of farm-gate sales revenue from each product class using 2004–

2008 mean commodity prices reported by Australian Bureau of Agricultural Resource

Economics (Thomas et al. 2010)

APSIM model

The crop model was run to simulate daily values for zadok’s stage, green biomass and

animal grazing start and end days for grazing the wheat crops using daily weather data

for the chosen years and management rules for crop and livestock (Appendix 2). The

simulation was used to determine which days in each year that wheat crops were

available for grazing for each site based on zadok’s stage (GS < 31) and wheat green

biomass (> 200 kg/ha for spring wheat cultivar and > 500 kg/ha for the dual-purpose

winter wheat variety).

Wheat crops management

Two management systems for wheat cultivars (winter and spring) were described using

‘rule-based coding’ in the APSIM program. The dual-purpose winter wheat cultivar

‘Wedgetail’ was selected for use in this study, which has the advantages of higher grain

Commodity Units Price

Meat Finished lambs $/kg live weight 6.65

Adult ewes $/head 212

Rams $/head 500

Cast for age $/kg 119

Wool Ewes $/kg 0.08

Lambs $/kg 0.08

Grain Lupin $/tonne 200

Barley, crushed $/tonne 300

Lucerne pellets $/tonne 280

Others Pasture management $/ha 62

Shearing costs (adults) $/head 6

Shearing costs (lambs) $/head 5

33

quality than many dual-purpose wheat varieties (Miyan and Clune 2008). Spring wheat

cultivar ‘Wyalkatchem’ was chosen on the basis of local common use. Both wheat

varieties were planted at 150 plants/m2 with row spacing of 250 mm and sowing depth

of 30 mm.

Sowing time was controlled by a sowing rule. Each year, ‘Wyalkatchem’ was sown

from 25 April and Wedgetail from 15 March, after at least 10 mm of rain had occurred

over no more than 5 days, and crops were sown irrespective of rain on 1 July if there

had been no prior opportunity, for both wheats cultivates. The amount of starter

fertiliser at sowing applied each year for both wheat crops was 150 kg/ha of urea-

Nitrogen (N) fertiliser. Surface organic matter was reset to 1000 kg/ha of wheat stubble

each year.

Livestock management

In the APSIM model, livestock component was used only to create a grazing event in

the wheat crops when grazing opportunities existed each year (Appendix 3). The

livestock enterprise at each of the three locations was based on Merino ewes, with

standard referencing weight 50 kg at 12 months of age at the time of first grazing.

Merino ewes were purchased when the amounts of FOO were exceeding 200 kg/ha and

500 kg/ha for the spring wheat cultivar and the dual-purpose winter wheat

correspondingly, and were sold when animals reached 50 kg. Stocking rate at each site

was 12.7 at Kojonup, 6.9 at Wickepin and 3.1 DSE/ha at Merredin. Wheat grazing

commenced when wheat biomass was more than 200 kg/ha for spring wheat cultivar

and 500 kg/ha for dual-purpose winter wheat variety, but crops were only grazed up

until they reached Zadoks growth stage GS31. This threshold is critical since grazing

beyond this phenological stage significantly delays wheat crop regrowth and recovery

from defoliation (Virgona et al. 2006).

34

Spread sheet analysis

Grazing wheat crop varieties analysis

Given that we assumed lucerne pellets represented the winter and spring wheat cultivar

forage in the GrassGro model, a combination of Microsoft Excel version 2010 and the

modelling outputs was used to determine flock ewes’ daily crop intake each year at

three sites. Two scenarios (crops grazed and crops ungrazed) were assumed to obtain

total crop metabolisable energy intake (MJ/ha/day), grazing wheat crops values ($/ha),

and durations of grazing days (DSE/ha) every year. If the green biomass of the dual-

purpose winter wheat crop was greater than 500 kg/ha within the period of wheat

Zadoks stage below 31, and if the total pasture green biomass was more than 800 kg/ha,

animals were allowed to graze winter crops ‘grazed treatment’. Conversely, if both

crops and pastures biomass was less than the specified levels, flock ewes were fed with

lucerne pellets in the feedlot paddocks and the animals in all treatments were considered

to be not grazing crop. Similar assumptions were used for grazing the spring wheat

cultivar, except that the grazing of this cultivar commenced when the shoot mass of the

wheat crops reached 200 kg/ha.

The total ewe flock ME intake of wheat crop MJ/ha/day (GWi) was calculated as below:

GWi = (12.3 × MEi × n) / 700 ha (3)

Where:

12.3 is the ME content (MJ/kg DM) of lucerne pellets

MEi is total flock ewes wheat crop ME intake per day

n is total number of flock ewes per hectare

700 is the crop area being grazed

Gross margin

The GrassGro model was used to calculate the gross margins (GM) of farm and

enterprise based (pasture and livestock), using 2011 Australian commodity prices

(ABARE 2011). GM was determined as gross revenue minus variable farm costs. The

farm revenue ($/ha) was from the sales of livestock and wool. Farm profit from the

yield of wheat grain was not included in this study. In order to evaluate farm profit with

35

and without grazing wheat crops, several criteria were applied. The value of grazed

wheat crops was determined as the annual total metabolisable energy (ME) of wheat

crops that was consumed per hectare multiplied by the cost of ME intake ($/MJ) each

year.

Annual wheat (winter and spring) grazing value (GWv) was calculated:

GWv = GWi × c (4)

Where:

GWi is ME wheat intake per year (MJ/ha/year)

c is the cost of lucerne pellets per MJ intake (0.23 $/MJ)

Years with less than 7 days grazing of wheat crops were considered to be practically not

worth grazing, and were assigned a zero value for number of days of crop grazing. The

gross margin from grazing of crops was calculated as the summation of the marginal

value of grazing wheat crops and farm gross margin.

Statistical analyses

A three-way ANOVA (repeated measures) analysis using GenStat (GenStat 2010) was

conducted to determine the effect of location (high, medium and low rainfalls) ×

wheat type (winter and spring) x time (across 50 years) on farm gross margin.

Treatments with and without grazing of the winter and spring wheat cultivar were

used as the significant variables (factors) and the five soil fertility scalars (0.7, 0.75,

0.8, 0.85 and 0.9) were used as nominal factors. In this simulation experiment, time

(years) was used as replicates. Residual plots were examined for the ANOVA test to

ensure that the assumptions of normality and homogeneity of variance were

appropriate. Tukey’s multiple comparison tests using GenStat were conducted to

determine the differences between the individual mean values of the gross margin in

the interaction between location and both treatment groups.

36

Chapter Three

Results

The duration of cereal grazing

The opportunity for grazing the two wheat cereal crops varied among the three Western

Australian locations. According to the rules used in the simulations, the location where

wheat crops grazing opportunities occurred most often was at the driest site, with

grazing of the dual-purpose winter wheat crop in 65% of years and the spring wheat

cultivar in 31% of years (Table 3).

Table 3. The proportion of years that wheat crops (winter and spring) are grazed and the

average duration of grazing wheat crops in those years where wheat crops grazing

opportunity occurrs in the three regions of Western Australia

Location DSE grazing days

(day/ha) Duration of grazing days

(days) Proportion of years crops

are grazed (%) DP winter wheat

Kojonup 433 25 55 Wickepin 201 21 50 Merredin 132 29 65

Spring wheat cultivar Kojonup 242 16 15 Wickepin 127 15 22 Merredin 50 13 31

In contrast, the grazing opportunities of the dual-purpose winter wheat cultivar were

least frequent at Wickepin (50% of years), and for the spring wheat cultivar at Kojonup

(15% of years) (Table 3). The long-term average for the crop grazing days shown in

Table 3 indicted that the duration of grazing days (for the two wheat types) fluctuated

37

between and within locations. At Merredin, the duration of grazing days was more

variable (13 to 29 days) when spring wheat cultivar and dual-purpose winter wheat crop

were grazed respectively. The duration of wheat crops grazing days was consistently

longer (1.7 times) with winter variety than the corresponding spring variety at each site

(Table 3).

Effects of grazing wheat crops on supplementary feeding cost

Supplementary feed costs where grazing of winter and spring crop was permitted were

reduced across locations (from A$ 358/ha to A$ 306/ha and to A$ 347/ha for total

supplement costs respectively). The reduction in costs varied among locations and

depended on the variety of wheat crops grazed (Table 4). For example, the grazing of

dual-purpose winter wheat crop reduced the total costs of supplementary feeding by

15% at Kojonup and 19% at Merredin. Whereas, at these locations, supplementary

feeding cost declined by 3% when the spring wheat cultivar was grazed. In addition, the

reduction in annual cost for supplementary feeding was 5.3 times greater at Kojonup

when dual-purpose winter wheat was grazed compared with the spring wheat cultivar

(A$ 85/ha v. A$ 16/ha; Table 4).

Table 4. Supplementary feed costs in a prime lamb enterprise without and with the

grazing of winter and spring wheat crops at three locations in Western Australia. DP,

Dual-purpose wheat variety

Location Total supplement costs

without grazing crops $/ha

Total supplement costs with grazing crops

$/ha

Change in supplement

cost $/ha

DP winter wheat

Kojonup 559 474 85 Wickepin 339 302 37 Merredin 178 144 34

Spring wheat cultivar Kojonup 559 543 16 Wickepin 339 327 12 Merredin 178 172 6

38

There were meaningful variations in the change of supplementary feed costs across each

of the regions by grazing wheat crops (Table 4). These variations ranging from A$

34/ha at Merredin to A$ 85/ha at Kojonup with the use of dual-purpose winter wheat,

and from A$ 6/ha at Merredin to A$ 16/ha at Kojonup with the grazing of spring wheat

cultivar. The simulation modelling results indicated that despite the greater reduction in

supplementary feed cost at Merredin, it has a corresponding lower increase in total farm

profit.

Effects of grazing wheat crops on profit from lamb production enterprises

The integration of dual-purpose winter wheat and a spring wheat cultivar in a lamb

production system increased farm profit among the three locations of Western Australia

(P<0.001; Table 5). However, the farm returns from grazing wheat crops varied across

locations and wheat types. More specifically, when the grazing of dual-purpose winter

wheat was permitted, farm profit increased by A$ 43/ha at Kojonup, A$ 19 /ha at

Wickepin and A$ 17/ha at Merredin. In contrast, the grazing of a spring wheat cultivar

increased the annual farm profitability from A$ 2/ha Merredin at to A$ 7/ha at Kojonup

(Table 5).

Table 5. Annual farm gross margins predicted by simulation modelling. With

dual-purpose (DP) winter wheat grazing (WG), spring wheat cultivar grazing (SG)

or without grazing (NO G)

*Values representing the profitability of grazing the two wheat varieties at Western

Australia locations were calculated over 50 years. Differences between the mean values

in both treatment groups were tested for significance using Tukey’s multiple

comparison tests (P<0.05) in GenStat.

Location

*Gross margin ($/ha) Change in gross margin ($/ha)

No G WG SG WG SG

Kojonup 1094a 1137b 1101a 43 7

Wickepin 576c 595c 581c 19 5

Merredin 221d 238d 223d 17 2

Mean 630 657 635 26 5

39

The relative profitability of lamb production enterprises differed across seasons between

the three study sites as indicated by a location × time (years) interaction (P<0.001).

Using the simulated cumulative distributions of farm profit, the profitability of

enterprises varied within and between locations each year, when wheat crops were made

available for grazing at each of the sites (Fig. 5). For example, over 50 years, farm

returns varied at each of the three site, ranging from A$ 831/ha to A$ 1377/ha at the

high rainfall area, from A$ 377/ha to A$ 758/ha at the medium rainfall and from A$

143/ha to A$ 327/ha at the low rainfall location. There was an interaction between

wheat varieties and time (i.e fluctuations in seasonal rainfalls) on the annual farm

profitability (P<0.001).

Cumulative distribution of farm profit values ($/ha) by grazing wheat crops are

presented in Fig. 6. The value of grazing dual-purpose winter wheat crops varied from

year-to-year. For instance, the simulations predicted that enterprise returns were the

lowest in 1977 (A$ 513/ha) and the highest in 1999 (A$ 822/ha) by grazing dual-

purpose winter wheat. Similarly, there were seasonal variations in farm profit when

spring cultivar was grazed, ranging from A$ 518/ha to A$ 762/ha.

40

Fig. 5. Simulated cummulative distribution of the profitability of lamb production enterprises

(expressed as gross margin $/ha) when wheat crops were grazed at three locations in Western

Australia. Each curve comprised 50 seasons from 1960 to 2009.

Across all Western Australia regions, the average marginal value of grazing dual-

purpose winter wheat was 5 fold higher than that of grazing the spring wheat cultivar

(mean value A$ 26/ha versus A$ 5/ha; Table 5). There was no interaction between

region and grazing of wheat crops on the overall GM of lamb production enterprises (P

= 0.59). Farm GM for the Wickepin site did not differ for spring wheat cultivar and

dual-purpose winter wheat variety (A$ 238/ha v. A$ 223/ha; Table 5). Nevertheless, a

significant three-way interaction was observed between the grazing wheat crops ×

location × time (year), which increased the complexity of the analysis to assess the key

effect of the treatments under investigation.

0

200

400

600

800

1000

1200

1400

1600

0.00 0.20 0.40 0.60 0.80 1.00 1.20

The

prof

itabi

lity

of la

mb

prod

uctio

n en

terp

rises

with

gr

azin

g w

heat

cro

ps ($

/ha)

Cumulative probability

Kojonup Wickepin Merrdin

41

Fig. 6. Simulated cumulative distribution of the profitability of lamb production enterprises

(expressed as gross margin $/ha) with or without grazing of wheat crops (winter and spring) at

three locations in Western Australia. Each curve comprised 50 season from 1960 to 2009.

The relationship between the change in supplementary feeding cost and duration

of grazing wheats

There was a negative correlation between supplementary feeding costs and grazing days

obtained from grazing wheat varieties (Fig. 7). The cost of supplementary feeding

reduced linearly with duration of wheat crops (winter and spring) grazing days. Each

DSE grazing day (days/crop ha) obtained from the dual-purpose winter wheat crop

reduced supplementary feeding cost by (A$ 0.21/ha, A$ 1.28/ha and A$ 1.70/ha) at

Kojonup, Wickepin and Merredin respectively (High, Medium and Low rainfall

locations). For the spring wheat cultivar, the predicted decrease in supplementary

feeding cost for each DSE grazing day was (A$ 0.06/ha, A$ 0.58/ha and A$ 0.75/ha) at

the three of Western Australia’s sites mentioned above correspondingly.

500

550

600

650

700

750

800

850

0.00 0.20 0.40 0.60 0.80 1.00 1.20

The

prof

itabi

lity

of l

amb

prod

uctio

n en

terp

rises

with

gr

azin

g w

heat

cro

ps ($

/ha)

Cumulative probability

without grazing wheat crops DP Winter Wheat Spring wheat cutivar

42

Fig. 7. The relationship between wheat crops (winter and spring) grazing days and the change in

supplementary feeding costs at the three sites of Western Australia. The solid line is the

regression line fitted between change in supplementary feed cost and DSE grazing crops.

The timing of grazing wheat cereals

Based on the assumptions highlighted in this study, the early sowing date of a dual-

purpose winter wheat crop meant that a large percentage of total grazing days

opportunities (in DSE/ha) fell in April-July at Kojonup and Wickepin, while at

Merredin grazing days fell in April-August (Fig. 8). As a result, only a small proportion

of the grazing of dual-purpose winter wheat crop was before weaning (20 May), and the

quantity of grazing days attributed to lactating ewes was low.

Across study sites, the requirement to reach 500 kg/ha biomass for the dual-purpose

winter wheat was most in July at both Kojonup and Wickepin (1081 and 238 DSE

y = 0.3898x - 2.8576 R² = 0.99859

y = 0.3828x + 0.3098 R² = 0.99871

y = 0.3927x - 0.5088 R² = 0.99863

y = 0.3972x + 0.0696 R² = 0.99995

y = 0.3974x - 0.0471 R² = 1

y = 0.3975x + 0.023 R² = 0.99993

0

100

200

300

400

500

600

700

0 200 400 600 800 1000 1200 1400 1600

Dec

reas

e in

sup

plem

enta

ry fe

edin

g co

st ($

/ha)

Average wheat grazing (DSE days/ha)

DP Winter wheat (Kojonup) DP Winter wheat (Wickepin) DP Winter wheat (Merredin) Spring wheat cultivar (Kojonup) Spring wheat cultivar (Wickepin) Spring wheat cultivar (Merredin)

43

grazing days/ha respectively), while in Merredin was on June (147 DSE days/ha) and

August (197 DSE days/ha). However, for the spring wheat cultivar, a substantial

proportion of the total grazing days fell in the June and August period (147 and 197

DSE days/ha). In the three Western Australia sites, the total amount grazing (DSE/ha)

was generally greater when a dual-purpose winter wheat crop was grazed than the

corresponding spring wheat cultivar. For example, there were about 4 times more

grazing days with the dual-purpose winter wheat were higher compared with spring

wheat cultivar at Kojonup (1081 vs. 258 DSE days/ha on July; Fig. 8).

44

0

200

400

600

800

1000

1200

April May June July Augest

DSE

graz

ing

days

/ha

Month

(a)  

0

200

400

600

800

1000

1200

April May June July August

DSE

graz

ing

days

/ha

Month

(c)  

0

200

400

600

800

1000

1200

April May June July August D

SE

graz

ing

days

/ha

Month

(b)  

Fig. 8. Long-term average monthly distributions of grazing wheat cereal varieties in DSE

days/ha at (a) Kojonup, (b) Wickepin and (c) Merredin. Dual-purpose winter wheat culivar

(grey fill); Spring wheat cultivar (black fill). Data were averaged for 50 seasons from 1960-

2009.

45

Chapter Four

Discussion

The inclusion of grazing wheat crops in a mixed-farming system generally reduced farm

supplementary feeding cost and improved farm gross margin in the three wheatbelt

regions of Western Australia, even at the driest site. The profitability of lamb

production enterprises was generally lower when both wheat crops were excluded from

grazing at the three sites of Western Australia. However, the profitability of farms

varied across study sites and grazing wheat systems over time. A substantial proportion

of total grazing days on wheat crops fell during the period of winter feed shortage. The

evidence from this simulation support the hypothesis that integrating grazing wheat

crops in lamb production systems will increase farm profit and partially fill the winter-

feed gap across a range of regions in Western Australia, and reduce supplementary

feeding costs.

Grazing wheat crops for several weeks during winter-feed gap period can be a potential

alternative to traditional feeding at this time, which is costly. Moreover, winter and

spring wheat crops are an important low-cost source of feedbase that could provide

green forage when annual pasture has not grown enough to be grazed and when grazing

is managed carefully so that yield penalties are avoided (Doole et al. 2009; Moore

2009).

The frequency of grazing both wheat crops generally varied over time across the rainfall

gradient for the locations due to an interaction between wheat type and time (years).

Nevertheless, the proportion of years where dual-purpose winter wheat was grazed was

comparatively high, even at the low rainfall site. It was hypothesised that the returns

from grazing wheat crops would be increased steadily every year at each location.

However, year-to-year variation in the relative availability of pastures due to seasonal

fluctuation in rainfalls had a significant effect on the utilisation of cereal wheats for

grazing. For example, at the low rainfall location, dual-purpose winter wheat was

grazed more frequently (65% of years) than high rainfall area (55% of years) because

winter pasture availability was low at the time when crops reached growth stage (GS30)

and were available for grazing. Therefore, grazing wheat crops will be most valuable

46

and practicable in years where pasture growth is expected to be low due to decline in

the annual rainfalls or during seasons with low winter rainfall.

The model outputs indicate that grazing the two wheat crops is a profitable practice

across the three rainfall locations. However, the largest returns from grazing wheat

crops were in the high rainfall site. A wide range of factors could explain the larger

increases in farm profit with the grazing of wheat crops in the high rainfall site. First,

the profitability of grazed wheat crops is not surprising since wheat and pasture biomass

productions is typically much greater in the high rainfalls region, relative to the low

rainfalls location, thus yielding more feed available to livestock. Secondly, the

variations in stocking rates across study regions were a driver of farm profit. A higher

average number of grazing days (433 DSE days/ha) obtained by grazing the dual-

purpose winter wheat were at the highest rainfall site, with stocking rates of 8.5 head/ha

compared with the driest site (132 DSE days/ha with stocking rate 2.14 head/ha).

Hence, the extra forage from a dual-purpose wheat crop will permit the highest relative

increases in stocking rates and thus increases farm profit in the high rainfall area.

The effects of stocking rate on the value of grazing wheat crop have been addressed by

several studies that have assessed the economic benefits of the utilization of wheat crops

in mixed-farming systems. For example, Moore (2009) demonstrated that the decreases

in stocking rate resulted in decreased total production of lamb and wool per ha when the

wheat crops were grazed (i.e. lamb production was decreased from 122 kg LW/ha to 99

kg LW/ha when stocking rate decreased from 4.3 to 3.5 ewes/ha in Merredin with

grazing of wheat crops). Similar findings were reported by Bathgate (2008) where farm

profit was increased by approximately A$ 8,000 by grazing when stocking rates

increased from 11 DSE/ha to 14 DSE/ha. In addition, Amjad et al. (2006) and Dove and

Salmon (2005) found that wheat crops could cope well with a grazing pressure of 25

DSE/ha without affecting grain yield. In contrast to previous studies, this study did not

explore the whole-farm economic value from grazing wheat crops and the value of

grazing these wheat crops with different stocking rates was also not explored, as the

stocking rate was maintained constant in the simulations modelling. Both topics are

consequently worthy of further examination.

47

The requirement for supplementary feeding was affected by the proportional increases

in grazing days obtained from wheat crops in the western regions. The highest reduction

in supplementary feedg cost achieved by grazing winter and spring wheat crops were at

the wettest site in Western Australia. The reason was that in high rainfall site, the

grazing intensity with dual-purpose winter wheat (433 DSE days/ha) and spring wheat

cultivar (242 DSE days//ha) was greater than in low rainfall region (132 and 50 DSE

days/ha respectively), which positively led to a greater reduction in supplementary feed

requirement in this region. Overall, the model output suggests that although grazed

wheat crops is an attractive and a profitable technology in high rainfall location, there

may well be scope for expanding the use of these cultivars into low rainfall location

particularly in years when pasture biomass production decreases due to low growing-

season rainfalls and long feed gaps. In addition, winter wheats are poorly adapted to this

type of season and crop yield could be negligible. As such in the driest part of Western

Australia, the inclusion of wheat crops in the farming system should not be regarded as

a replacement for supplementary feeding of livestock, but mainly as an adjunct to feed

supply.

Profit from grazing dual-purpose winter wheat versus a spring wheat cultivar

The profitability of lamb production enterprises was influenced by an interaction

between time (years) and the grazing systems of wheat crops. The model indicated that

over time, the profit from grazing the dual-purpose winter wheat cultivar was higher

than that of grazing spring wheat across all study locations. Dual-purpose winter wheat

is slow maturing and therefore offers a relatively long period for grazing before growth

stage reaches shoot mass GS30 (Moore 2009). Dual-purpose winter wheat can be sown

early (from late February to June), and that would have a result in higher yield without

increasing frost risk due to a strong vernalisation requirement (Barrett-Lennard et al.

2011). In our model, the window opportunity of grazing spring wheat cultivar was on

average shorter (15 days) when compared to grazing the dual-purpose winter wheat

variety (25 days). Thus, the requirements for supplementary feeding were higher (13%)

by grazing spring wheat cultivar and this may have affected the annual profitability of

lamb production enterprises.

48

An on-farm trial (Barrett-Lennard et al. 2011) and a simulation-modelling study of

grazed spring wheat cultivar (Moore 2009) conducted in the Western Australia

wheatbelt reported a similar number of grazing days from a spring wheat cultivar. In

contrast to dual-purpose winter wheat variety, early sowing of spring wheat cultivar can

be limited by the risk of frost damage if plants mature too early, which usually occurs in

late winter and, then, the plants are not able to recover from grazing to produce grain

(Virgona et al. 2006). Hence, grazing dual-purpose winter wheat suits areas with a long

growing season and usually an early and reliable autumn break (Doole et al. 2009). The

grazing of spring wheat is a relatively inflexible feed source that can only be utilized at

a particular time of the year in Western Australia. Further analysis of these modelling

outcomes is needed to determine whether the profit improvements are realistic, to

identify management challenges and risks associated with the inclusion of grazing

wheat crops in farming system and to identify more flexible grazing rules that capture

increased farm profit.

How often will wheat crops provide a winter forage resource? Based on simulation rules, winter and spring wheat crops will likely provide

opportunities for grazing during the winter-feed gap at all three sites in Western

Australia. The grazing of both wheat crops provides an affordable feed source from

April to early August at the study sites, when the majority of livestock is expected to be

in poor body condition following the autumn/winter feed gap. The value of grazing

wheat crops during the period of feed shortages has been reported in several studies

(Doole et al. 2009; Moore et al. 2009). For example, Doole et al. (2009) demonstrated

that per hectare whole-farm profit increased by 11% with the grazing of spring wheat in

the Great Southern regions.

Additionally, grazing wheat crops occurred less frequently at high rainfall location

where pasture productivity was high at the time when crops were available for grazing.

The time difference between pasture versus cereal crops grazing commencement is

shorter at high rainfall site than that of low rainfall location and vice versa (Thomas and

Moore 2011). Another modelling study showed that the grazing opportunity of spring

wheat crop was short or rare in the drier parts of Western Australia before the initiation

of reproductive stage and before the crop reached a shoot mass of 1000 kg/ha due to

49

quick phenological growth in the absence of vernalisation requirement (Moore 2009).

However, Moore (2009) suggested that to increase the window of opportunity for

grazing spring wheat, the shoot growth mass has to be lower than assumed in his study

and if the removal of reproductive meristems is to be avoided.

In comparison to Moore’s study, the shoot growth mass in our study was much lower

(200 kg/ha) and the sowing time of spring wheat was earlier (25 April) than that

assumed (1000 kg/ha by 1 May) by Moore (2009). This indicates that even with low

wheat shoot biomass; spring wheat cultivars could potentially provide a green feed over

a short period during winter-feed shortage. Lamb producers in low rainfall area should

benefit from the extra green forage provided by grazing both wheat crops when there is

a lack of feed in winter.

Estimating farm profit

Biophysical modelling with GrassGro was effective to estimate the level of

supplementary feeding required each season (from 1960 to 2009) for lamb production

system and in the three sites of Western Australia. Additionally, APSIM and GrassGro

models outputs predicted seasonal wheat crops and pastures growth rates respectively

for the chosen locations, and the variations in seasonal conditions from year to year

were also included. From a theoretical standpoint, the use of these types of models to

evaluate the productivities of pastures and crops, production costs and enterprises

profitability seems to be valid. In this model, the diverse costs ($/ha) associated with a

lamb production system can be estimated and included in the gross margin analyses.

This may be useful to calculate the outcomes to several possible scenarios and help the

farmer to choose a number of preferred options for further analysis, and to assess

financial and practical outcomes.

Key assumptions

As with any modelling study, this analysis makes several important assumptions. First,

we have only examined the production of pasture green biomass in the GrassGro model

with constant pasture species, which may have had an effect on the production of green

biomass and the level of crop grazing that was predicted in the simulation study. Other

50

pasture species could produce less biomass during the time when wheat crops have

grown enough to be grazed, which would create a longer opportunity for grazing.

Our simulations for the three sites of Western Australia were performed for a relatively

long period (1960-2009). A long period of time was chosen in order to sample a wide

range of possible climatic conditions, and to assess the profitability of lamb production

enterprises without or with the grazing of wheat crops under variable seasonal

conditions. The same analysis implemented on shorter periods of time may have

produced different results.

In our simulations, all prices were maintained constant over the 50 years. The use of

different prices and costs scenarios would affect the gross margins determined by the

simulations. For example, reduced or increased grain, lamb and wool sales prices and

other costs would generally impact on farm profitability differently, or the relative

values between locations and cultivar would have remained consistent though.

Furthermore, the value of grazing wheat crops during the winter period allows for the

potential to spell pastures, which can then be used by livestock at a later stage

(Nicholson et al. 2008; Doole et al. 2009; Moore et al. 2009). Placing livestock on

wheat crops in winter will have indirect effects by deferring grazing of the main pasture

area, resulting in higher pasture availability in the following spring and summer, which

could lead to substantial increases in profitability (Mokany et al. 2008). For instance,

the opportunity to graze livestock on winter crops for a month (from June 15 to July 15)

would increase gross margins by A$ 2.40/DSE by an additional 14% pasture

availability with grazing crops relative to continuous pasture (Nicholson et al. 2008).

However, the extra income from deferred pasture grazing was not included in our

simulation modelling because GrassGro does not support the wheat crop model.

In reality, producers in the mixed-farming systems may move animals into pasture later

than we assumed in the model (greater than 800 kg/ha DM), most probably in a good

seasons and at the time when wheat crops developed a reliable mass for grazing during

winter. In contrast, without the inclusion of the grazing wheat crops in a lamb

production system, lamb producers would need to move their animals into pasture

earlier than the time assumed in this study (less than 800 kg/ha). Further simulation

studies could examine the possible consequence of deferring pasture grazing by grazing

51

wheat crops on the profitability of lamb production enterprises. It is important to note

that based on the rules set for this study for the grazing of wheat crops, grain yields

penalties are likely to be negligible.

The profitability of grazing wheat crops depended on the grazing rules used in the

model, and any changes in these rules would significantly affect the value of wheat

crops determined in the simulations. For example, GrassGro does not support a crop

model in its plant management component. We used supplementary feeding of lucerne

pellets in the GrassGro plant model in place of wheat crops in this study, and it is likely

that a different plant model will change the output values for the study simulations. For

example, the quality and the quantity of wheat crops changed over time (Nicholson and

Falkiner 2009; Frischke 2011) while the corresponding supplementary feeding remained

the same, which may significantly impact on livestock productivity and farm

profitability. Frischke (2011) demonstrated that the amount of dry matter (DM 393

kg/ha vs. DM 164 kg/ha) and the value of grazing wheat (A$ 62/ha vs. A$ 23/ha)

increased with later grazing of GS 30 than GS 14 respectively. Nevertheless, the

approximated method used in this study provides an attractive outline to estimate the

potential value of grazed wheat crops in lamb production enterprises.

Conclusion

The study investigated the effects of grazing wheat crops (winter and spring) on the

profitability of lamb production enterprises in three different locations in Western

Australian, across a high to low rainfall transect. A modelling study was chosen because

the relative value of grazing wheat crops on mixed farms can be influenced by multiple

factors that are difficult to measure using other techniques. The results of our simulation

study suggested that grazing wheat crops could be a profitable strategy to compensate

the early winter feed gap by reducing supplement any feeding costs for a short period in

autumn. The grazing of both wheat varieties has the potential to generally reduce farm

supplementary feeding costs, and may be valuable in seasons with low pasture

productivity. Grazing of a dual-purpose winter wheat variety will be a valuable strategy

to producers in the high rainfall zones due to high wheat biomass production. Moreover,

farmers in the driest parts of the Western Australia Wheatbelt should also benefit from

grazing winter and spring wheat crops particularly in years with late pasture

52

establishment, but must consider potential yield penalties if they choose a dual-purpose

winter wheat variety. The window of opportunity for grazing the dual-purpose winter

wheat will be greater than that for the grazing of spring wheat cultivars. This is because

the dual-purpose winter wheat variety can be sown early and then produce green feed

for a long period before pasture mass reaches 800 kg/ha in a late season. Future

simulation studies could examine and identify more flexible grazing rules, which would

enhance the farm profitability by improving livestock production and wheat crops yield.

The profitability of grazed winter and spring wheat crops for each farm will be

different, as profit depends on all the possible combinations such as location, climatic

conditions, enterprise attributes (livestock breed and management) and wheat sowing

time and capacity. However, there are some general rules that help farmers to appreciate

the impacts and benefits from grazing wheat crops, at different times and for different

durations and intensities. Each individual producer will need to consider these pros and

cons and determine the best fit for their farm. Nonetheless, this type of investigation of

the farm profitability using a modelling study has the potential to enable livestock

producers to make a tactical decision with regards to seasonal weather conditions and to

help to better manage their animals by grazing wheat during periods of feed shortage.

53

References:

ABARE (2010) Australian lamb: Financial performance of slaughter lamb producing

farms, 2007–08 to 2009. Canberra. 10, 10.1.

ABARE (2011) Australian commodity statistics-2011. (Australian Bureau of

Agriculture and Resource Economics: Canberra).

ACIL (2009) A review of adjustments that would be required if live sheep exports from

Western Australia ceased. ACIL Tasman. Economic Policy Strategy.

Alford AR, Cacho OJ, Griffith GR (2006) A Bio-Economic Model of a Northern

Tablelands Cattle Grazing Enterprise. I. Specification and Validation of the

Model.

Amjad M, Sharma D, Curtis B, Anderson WK (2006) Dual purpose long season winter

wheats to improve productivity in Western Australia. In 'Proceedings of the 13th

Australian Agronomy Conference. 10-14 September 2006', Perth, Western

Australia, p. 9.9.

Anderson WK, Garlinge JR (2000) The wheat book: principles and practice.

Department of Agriculture, Western Australia: South Perth.

Anslow RC, Green JO (1967) The seasonal growth of pasture grasses. The Journal of

Agricultural Science 68 (01), 109-122.

Arnold G, Maller R, Charlick A, Hill J (1975) Lupin crops in pastoral systems for

weaner sheep in a Mediterranean environment. Agro-Ecosystems 2, 99-116.

Athas S (2011) Australian sheep industry projections 2011-mid-season update. Meat

and Livestock Australia.

Australian Soil Resource Information System - ASRIS (2006) Australian Collaborative

Land Evaluation Program (ACLEP) and CSIRO. Available at

http://www.asris.csiro.au/index_other.html (Verified on 27 July 2012)

Barber M (2009) The value of live sheep exports from Western Australia: A review of

adjustments that would be required if live sheep exports from Western Australia

ceased. ACIL Tasman Economics Policy Strategy.

Barber M, Chou Y (2009) Australian Live sheep exports: Economic analysis of

Australian live sheep and sheep meat trade. ACIL Tasman Pty Ltd. Reliance

104.

54

Barrett-Lennard P, Quinlan R, Taylor S, Warren G (2011) Grazing crops in winter has

little or no impact on grain yield and quality. Crop Updates, Perth 2011.

Bathgate A (2008) Effect of grazing winter crops on the most profitable enterprise mix.

the Grain and Graze Program on grazing winter crops. Grazing Winter Crops

Roadshow. Workshop Notes. Grain and Graze. March 2008. pp80

Baumhardt R, Schwartz R, Greene L, MacDonald J (2009) Cattle Gain and Crop Yield

for a Dryland Wheat-Sorghum-Fallow Rotation. Agronomy Journal 101, 150–

158.

Bell LW (2008) Simulating options for managing seasonal and annual variations in feed

supply of mixed crop/livestock systems in sub-tropical Australia, In

Multifunctional grasslands in changing world. In ‘Proceeding of the joint

meeting of 21st international grassland congress and 8th international rangelands

congress’, Hohhot, China, (Eds Organization Committee of the IGC/IRC) p.198.

Guangdong People's Publishing House.

Brown D, Crook B, Purvis I (2002) Differences in fibre diameter profile characteristics

in wool staples from Merino sheep and their relationship with staple strength

between years, environments, and bloodlines. Australian Journal of Agricultural

Research 53, 481-492.

Burnett V, Ponnampalam E (2011) Specialist Forages – Lamb Finishing Guidelines.

Agriculture Department of Primary Industries. Victoria, Australia.

Connell P, Hooper S, Helali S (2002) Australian Prime Lamb Industry 2002. Report of

the Australian Agricultural and Grazing Industries Survey of Prime Lamb

Producers.

Croker K, Curtis K, Speijers J (2009) Times of Lambing in Australian Flocks – 2005 to

2007. Department of Agriculture and Food, Western Australia: Wool Desk

Report –2009.

Croker K, Watt P (2001) The Good Food Guide for Sheep. Department of Agriculture

Western Australia, South Perth.

Devenish K, Hyder M (2001) Grazing Annual Pastures in The Good Food Guide for

Sheep. Eds Croker K, Watt P. Department of Agriculture, South Perth.

Donnelly J, Freer M, Salmon L, Moore A, Simpson R, Dove H, Bolger T (2002)

Evolution of the GRAZPLAN decision support tools and adoption by the

grazing industry in temperate Australia. Agricultural Systems 74(1), 115-139.

55

Donnelly J, Moore A, Freer M (1997) GRAZPLAN: Decision support systems for

Australian grazing enterprises—I. Overview of the GRAZPLAN project, and a

description of the MetAccess and LambAlive DSS. Agricultural Systems 54(1),

57-76.

Doole GJ, Bathgate AD, Robertson MJ (2009) Economic value of grazing vegetative

wheat (Triticum aestivum L.) crops in mixed-farming systems of Western

Australia. Animal Production Science 49, 807-815.

Dove H, Holst P, Stanley D, Flint P (2002) Grazing value of dual-purpose winter

wheats for young sheep. Animal Production in Australia 24, 53-56.

Dove H, McMullen KG (2009) Diet selection, herbage intake and liveweight gain in

young sheep grazing dual-purpose wheats and sheep responses to mineral

supplements. Animal Production Science 49, 749-758.

Dove H, Salmon L (2005) Whole-farm focus needed for grazing wheat. . Farming

Ahead, No. 156, pp 50-52.

DPI (2011) South West farm project moniter summary results 2010/2011. The

Department of Primary Industries.

Dowling E, Wiese S (2001) Sheep Meat Enterprises in Western Australia: In The Good

Food Guide for Sheep. Department of Agriculture Western Australia, South

Perth.

Dynes R, Henry D, Masters D (2003) Characterising forages for ruminant feeding.

Asian Australian Journal of Animal Scineces 16, 116-123.

Easta IJ, Foreman I (2011) The structure, dynamics and movement patterns of the

Australian sheep industry . Australian Veterinary Journal 89, 477..489.

Ewing M, Pannell D, Morrison D (1989) Pastures and profit in an Australian ley

farming system. In Proceedings of the XVI international grassland congress, 4–

11 October 1989, Nice, France.pp. 1349–1350.

Ewing MA, Flugge F, Kingwell R (2005) The benefits and challenges of crop-livestock

integration in Australian agriculture. CRC for Plant-Based Management of

Dryland Salinity SEA, Working paper no.2003, Perth. New directions for a

diverse planet. Proc. 4th Int. Crop Sci. Congr 26.

Finlayson JD, Cacho OJ, BywaterAC (1995) A simulation model of grazing sheep: I.

Animal growth and intake. Agricultural Systems 48, 1-25.

Fischer R, Turner NC (1978) Plant productivity in the arid and semiarid zones. Annual

Review of Plant Physiology 29, 277-317.

56

Fletcher S, Buetre B, Morey K (2009) The value of the red meat industry to Australia.

ABARE research report 09.13 for the Australian Government: Department of

Agriculture, Fisheries and Forestr. Canberra.

Freebairn B (2005) Productive dual purpose winter wheats. NSW Department of

Primary Industries. Agnote, ISSN 1034-6848.

Freer M, Dove H, Nolan J (2007) Nutrient requirements of domesticated ruminants.

CSIRO publishing pp.296.

French RJ (1987) Future Productivity on our Farmlands. In ' Proceedings of Fourth

Australian Agronomy Conference, Latrobe University'.

Frischke A (2011) Early winter grazing of crops intended for grain. BCG Season

Research Results.

GenStat (2010) 'GenStat for Windows 13th Edition: version 13.3.0.5165.' (VSN

International Ltd).

Gibberd MR, Turner NC, Loveys BR (2000) High vapour pressure deficit results in a

rapid decline of leaf water potential and photosynthesis of carrots grown on free-

draining, sandy soils. Australian Journal of Agricultural Research 51, 839-848.

Goers H, Jolly S (2007) A producers guide to production feeding for lamb growth. Meat

and Livestock Australia Limited. ISBN: 9 7817 4191 1060.

Griffith G, Vere D, Bootle B (1995) An integrated approach to assessing the farm and

market level impacts of new technology adoption in Australian lamb production

and marketing systems: the case of large, lean lamb. Agricultural Systems 47,

175-198.

Hanrahan P (1994) Drought feeding and management of sheep. A guide for farmers and

land managers. Victorian Government. Department of Primary Industries.

Catchment and Agriculture Services.

Harrison MT, Evans JR, Dove H, Moore AD (2011) Dual-purpose cereals: can the

relative influences of management and environment on crop recovery and grain

yield be dissected? Crop and Pasture Science 62, 930-946.

Hassall and Associates Pty Ltd (2000) Economic contribution of the live export

industry. Meat and Livestock Australia: Sydney, Australia.

Hassall and Associates Pty Ltd (2006a) The Live Export Industry; Value, Outlook and

Contribution to the Economy.

57

Hassall and Associates Pty Ltd (2006b) The Structure and Dynamics of the Australian

Sheep Industry. Department of Agriculture, Fisheries and Foresty. NSW: ABN

95 001 211 007.

Havilah E, Warren H, Lawrie R, Senn A, Milham P (2005) Fertilisers for Pastures. State

of New South Wales-NSW Department of Primary Industries.1st ed. ISBN 0

7347 1646 X.

Hill N, Zhang H, Trezise T, Young J, Moyes N, Carslake L, McTaggart R, Turner NC,

Anderson W, Poole M (2005) Successful Cropping in The High Rainfall Zone

of Western Australia. Crop research and extension in the zone. The Department

of Agriculture Western Australia.

Hinton DG, Lacey E, CSIRO (2006) Running a small flock of sheep. ISBN:

0643092757, CSIRO.

Hooper S, Blias A, Ashton D (2003) Australian Prime Lamb Industry. ABARE

Research Report 03.2, Canberra.

IPCC (2007) Climate Change 2007: Synthesis Report. An Assessment of the

Intergovernmental Panel on Climate Control. p. 52.

Jolly S, Wallace A (2007) Best practice for production feeding of lambs: a review of the

literature. Meat and Livestock Australia Limited. Locked Bag 991. North

Sydney NSW 2059.

Keating BA, Carberry PS, et al. (2003) An overview of APSIM, a model designed for

farming systems simulation. European Journal of Agronomy 18(3–4), 267-288.

Kelman WM, Dove H (2009) Growth and phenology of winter wheat and oats in a dual-

purpose management system. Crop and Pasture Science 60, 921-932.

Keniry J, Bond M, Caple I, Gosse L, Rogers M (2003) Livestock export review: final

report. Department of Agriculture. Fisheries and Forestry, Canberra, Australia.

Kenny P (1984) The growth of weaner sheep on clover or grass pastures during summer

in Western Victoria. Australian Journal of Experimental Agriculture and Animal

Husbandry 24, 144–149.

Kenny P, Reed K (1984) Effects of pasture type on the growth and wool production of

weaner sheep during summer and autumn. Australian Journal of Experimental

Agriculture and Animal Husbandry 24, 322–331.

Kerr P (2000) A guide to improved lamb growth. Palmeston North, New Zealand: New

Zealand Sheep Council.

58

Kingwell RS, Pannell DJ, Robinson SD (1993) Tactical responses to seasonal

conditions in whole-farm planning in Western Australia. Agricultural

Economics 8, 211-226.

Kirkegaard J, Sprague S, Marcroft S, Dove H, Duff C (2007) Grazing oilseed brassicas–

an economic and agronomic evaluation for Australian conditions. In

‘Proceeding. 15th Austraila. Research Assembly on Brassicas’ (Geraldton, 10-

14 September) 50-56.

Kirkegaard JA, Sprague SJ, Dove H, Kelman WM, Marcroft SJ, Lieschke A, Howe GN,

Graham JM (2008) Dual-purpose canola—a new opportunity in mixed farming

systems. Australian Journal of Agricultural Research 59, 291-302.

MansoT, Mantecón A, Giráldez FJ (1998) Animal performance and chemical body

composition of lambs fed diets with different protein supplements. Small

Ruminant Research 29, 185-191.

Martin GB, Rodger J, Blache D (2004) Nutritional and environmental effects on

reproduction in small ruminants. Reproduction, Fertility and Development 16,

491-501.

Masters D, Purser, D, Yu S, Wang Z, Yang R, Liu N, Lu D, Wu L, Ren J, Li G (1993)

Mineral nutrition of grazing sheep in northern China. I. Macro-minerals in

pasture, feed supplements and sheep. Asian-Australasian Journal of Animal

Science 6, 99-105.

McClymont GL, Lambourne J (1958) Interactions between planes of nutrition during

early and late pregnancy. In ‘Proceedings of the Australian Society of Animal

Production’ 2: 135.

McCormick JI, Virgona J, Kirkegaard JA (2011) Exploring opportunities for dual-

purpose canola in south–eastern Australia using crop simulation models, 17th

Australian Research Assembly on Brassicas (ARAB). Wagga Wagga, NSW.

(Eds D Luckett, D MacCaffery, H Raman, R Raman) pp. 184–188. (NSW

Department of Primary Industries: Orange).

McDonald P, Greenhalgh J, Morgan C (2002) ‘Animal nutrition’. Addison-Wesley

Longman Ltd.

McFarland I, Curnow M, Hyder M, Ashton B, Roberts D (2005) Feeding and

management sheep in dry times. the Department of Agriculture and Food

Western Australia (DAFWA) and Primary Industries and Resources South

Australia (PIRSA). Bulletin 4697. ISSN 1833-7236.

59

McMullen KG, Virgona JM (2009) Dry matter production and grain yield from grazed

wheat in southern New South Wales. Animal Production Science 49, 769–776.

Meat and Livestock Australia (2004a) Australian Lamb: Australian Sheep Industry.

Available at:

http://adl.brs.gov.au/data/warehouse/pe_abarebrs99001116/PC12848.pdf.

(verified 24 March 2012).

Meat and Livestock Australia (2004b) Australian sheep industry productivity Available

at http://adl.brs.gov.au/data/warehouse/pe_abarebrs99001116/PC12848.pdf.

(verified 24 March 20120).

Meat and livestock Australia (2006) Fast Facts 2006: Australia’s Sheep Meat industry.

Sydney: Australia.

Meat and livestock Australia (2010) Australia’s Sheep Meat Industry. Available at:

http://www.mla.com.au/About-the-red-meat-industry/Industryoverview/Sheep.

(verified 4 April 2012).

Meat and livestock Australia (2011a) Australia's sheepmeat industry. Available at:

http://www.mla.com.au/About-the-red-meat-industry/Industry-overview/Sheep.

(verified 9 April 2012).

Meat and livestock Australia (2011b) Australian livestock export statistical review

2010/2011.

Meat and Livestock Australia (2012a) MLA Australian sheep industry projections 2012

- mid-season update: 5 MLA sheep industry projections mid-season update -

Australian lamb market. Available at http://www.mla.com.au/Prices-and-

markets/Trends-and-analysis/Sheepmeat-and-lamb/Forecasts/MLA-Australian-

sheep-industry-projections-2012-mid-season-update/5-MLA-sheep-industry-

projections-mid-season-update-Australian-lamb-market.

Meat and Livestock Australia (2012b) MLA Australian sheep industry projections 2012

: 6 MLA sheep industry projections mid season update - lamb exports.

Available at http://www.mla.com.au/Prices-and-markets/Trends-and-

analysis/Sheepmeat-and-lamb/Forecasts/MLA-Australian-sheep-industry-

projections-2012-mid-season-update.

Michalk D, Saville D (1979) Supplementary feeding of range sheep. Journal of Range

Management 422-429.

Milne JA (1991) Diet selection by grazing animals. In ‘Proceedings of the Nutrition

Society’ 50, 77-85.

60

Milton J (2001) Lot-Feeding Prime Lambs: The Good Food Guide for Sheep.

Department of Agriculture, South Perth.

Milton J, Paterson J, Roberts D (2001) Principles of Ruminant Nutrition: The Good

Food Guide for Sheep Department of Agriculture, South Perth.

Miyan S, Clune S (2008) Effects of grazing on wheat grain yield and quality in Western

Australia. Global issues paddock action. In ‘Proceeding of the 14th Australian

Agron’. Adelaide, Australia.

Mokany K, Moore AD, Graham P, Simpson RJ (2010) Optimal management of

fertiliser and stocking rate in temperate grazing systems. Animal Production

Science 50(1), 6-16.

Mokany K, Salmon E, Moore (2008) A Grazing dual-purpose cereals during winter can

boost pasture production and profitability. pp. 132-137.

Moore AD (2009) Opportunities and trade-offs in dual-purpose cereals across the

southern Australian mixed-farming zone: a modelling study. Animal Production

Science 49, 759-768.

Moore AD, Bell LW, Revell DK (2009) Feed gaps in mixed-farming systems: insights

from the Grain and Graze program. Animal Production Science 49, 736-748.

Moore AD, Salmon L, Dove H (2004) The whole-farm impact of including dual-

purpose winter wheat and forage brassica crops in a grazing system: a simulation

analysis. In New directions for a diverse planet. In ‘Proceedings of the 4th

international crop science congress, Brisbane, Australia, 26 September–1

October 2004’. (The Regional Institute Ltd: Gosford, NSW) Available at

http://www.cropscience.org.au/icsc2004/symposia/6/3/693_mooread.htm.

Moore G, Sanford P, Wiley T (2006) Perennial pastures for Western Australia.

Department of Agriculture and Food, Government of Western Australia,

Bulletin No. 4690.

Mullany PD (1966) The influence of time of lambing on the performance of fine wool

merino ewes. In ‘Proceeding of The Australian Socity of Animal’. 6:198.

Nicholson C, Falkiner S (2009) The Impact Of Grazing At Different Growth Stages On

Drymatter, Grain And Stubble Of Two Wheat Varieties - Mininera, Vic.

Cropping & Grazing, Grain & Graze Trials. www.sfs.org.au.

Nicholson C, Kessell D, Miyan S, Clune S, Sage B, Martin T, Dean G, Falkiner S,

Mickan F, Watson W, Ashton BA, McInerney E, Prance T, Shahzad Z, Sait K,

Drew J, Barrett-Lennard P, Wiley T, Dove H, Salmon L and Bathgate A (2008)

61

Free food for thought. Grazing Winter Crops RoadshowWorkshop Notes. The

Grain and Graze Program on grazing winter crops.

Nix H (1975) The Australian climate and its effects on grain yield and quality.

Australian field crops 1, 183-226.

NRC (1985) National Research Council. Nutrient requirements of sheep, Subcommittee

on Sheep Nutrition, Committee on Animal Nutrition, Board on Agriculture,

National Research Council. National Academy Press: Washington, D.C., USA.

Norman H, Masters D (2010) Animal production from extensive grazing system.

Department of Agriculture and Food.

Nugent T, Milton J (2004) Merino feedlotting fills supply gap. Farming Ahead:

Livestock, Lambs: No.145.

Oddy V, Sainz R, Freer M, Dove H (2002) Nutrition for sheep-meat production. Sheep

nutrition 237-262.

Phy TS, Provenza FD (1998) Eating barley too frequently or in excess decreases lambs'

preference for barley but sodium bicarbonate and lasalocid attenuate the

response. Journal of Animal Science 76, 1578.

Ramirez RG (1999) Feed resources and feeding techniques of small ruminants under

extensive management conditions. Small Ruminant Research 34, 215-230.

Robertson M, Bathgate A, Moore A, Lawes R, Lilley J (2009) Seeking simultaneous

improvements in farm profit and natural resource indicators: a modelling

analysis. Animal Production Science 49(10), 826-836.

Robertson M, Gaydon D, Hall D, Hills A, Penny S (2005) Production risks and water

use benefits of summer crop production on the south coast of Western Australia.

Australian Journal of Agricultural Research 56, 597-612.

Sheales T (1999) Australian lamb production and global traade prospects. In 'Lamb

Industry Convention and Exhibition 1999. Sydney'. Volume 99.22 (ABARE

project 1676).

Smith I, McIntosh P, Ansell T, Reason C, McInnes K (2000) Southwest Western

Australian winter rainfall and its association with Indian Ocean climate

variability. International Journal of Climatology 20, 1913-1930.

Standing Committee on Agriculture (1990) Feeding Standards for Australian Livestock.

Melbourne: CSIRO Publications.

62

Taplin DE, Everitt GC (1964) The influence of pre-natal nutrition on post- natal

performance of Merino lambs. In ‘Proceeding of The Australian Society of

Animal Production. 5: 72’.

Thomas DT, Finlayson J, Moore AD, Robertson MJ (2010) The profitability of grazing

crop stubbles may be over-estimated by using metabolizable energy intake from

the stubble. Animal Production Science 50, 699–704.

Thomas DT, Milton J, Revell C, Ewing M, Dynes R, Murray K, Lindsay D (2010)

Preference of sheep among annual legumes is more closely related to plant

nutritive characteristics as plants mature. Animal Production Science 50, 114-

123.

Thomas DT, Moore AD (2011) Intergrating dual-purpose wheat to reduce supplement

feeding in mixed crop and livestock farms in south-western Australia. In

'Proceeding of the 8th International Symposium on the Nutrition of Herbivores.

Aberystwyth, Wales, UK, 6-9 Septemper. p.533'.

Thomas DT, Rintoul AJ, Masters DG (2007) Increasing dietary sodium chloride

increases wool growth but decreases in vivo organic matter digestibility in sheep

across a range of diets. Australian Journal of Agricultural Research 58, 1023-

1030.

Thompson A, Hynd P (1998) Wool growth and fibre diameter changes in young Merino

sheep genetically different in staple strength and fed different levels of nutrition.

Australian Journal of Agricultural Research 49, 889-898.

Turner NC (2004) Sustainable production of crops and pastures under drought in a

Mediterranean environment. Annals of Applied Biology 144, 139-147.

Ulyatt M (1981) The feeding value of herbage: can it be improved. New Zealand

Agricultural Science 15, 200-205.

Virgona JM, Gummer FAJ, Angus JF (2006) Effects of grazing on wheat growth, yield,

development, water use, and nitrogen use. Australian Journal of Agricultural

Research 57, 1307-1319.

Warn L, Webb Ware J, Salmon L, Donnelly J, Alcock D (2006) Analysis of the

profitability of sheep wool and meat enterprises in southern Australia. Final

report for project 1, 6.

Weiss W (1993) Predicting energy values of feeds. Journal of Dairy Science 76 (6),

1802-1811.

63

Western Australia Climate Services Centre (2010). A very dry year so far in southwest

Western Australia, Bureau of Meteorology, Special Climate Statement 21.

Zhang H, Turner N, Poole M, Simpson N (2006) Crop production in the high rainfall

zones of southern Australia-potential, constraints and opportunities. Australian

Journal of Experimental Agriculture 46, 1035-1050.

64

Appendix 1

GrassGro farm system components

65

Appendix 2

APSIM stimulation model: farm system components and weather data file example

66

Appendix 3

Grazing wheat crops output report generated using APSIM simulation modelling.

67

Appendix 4

Journal Formatting: Animal Production Science