IMPROVED UTILISATION OF BAUHINIA ACUMINATAsdh.hueuni.edu.vn/attachments/article/1363/... · tannins (Silivong and Preston, 2015). Water spinach (Ipomoea aquatica) is cultivated for

HUE UNIVERSITY

UNIVERSITY OF AGRICULTURE AND FORESTRY

PHONEVILAY SILIVONG

IMPROVED UTILISATION OF BAUHINIA ACUMINATA

FOR GOAT PRODUCTION IN LAO PDR

SPECIALIZATION: ANIMAL SCIENCES

CODE: 9620105

SUMMARY OF DISERTATION IN ANIMAL SCIENCES

HUE, 2020

This dissertation is completed at University of Agriculture and Forestry, Hue University

Suppervised by:

1. Associate Professor Dr. Nguyen Huu Van

2. Dr. Dương Thanh Hai

1st reviewer:……………………………………………………………………………………………………………

2nd reviewer: ……………………………………………………………………………………………………………

3rd reviewer: ……………………………………………………………………………………………………………

The dissertation will be defended at the Council of dissertation assessment of Hue University,

04 Le Loi Street, Hue city, at………….on ……../………../2020

Dissertation can be further referred at:

1. National Library

2. Center for Information and Library of Hue University of Agriculture and Forestry

1

INTRODUCTION

1. PROBLEM STATEMENT

Laos is located in the central part of the Indochinese Peninsula. It is an inland state

surrounded by China, Vietnam, Cambodia, Thailand and Myanmar. Laos has a total land area of

236,800 km2. The agricultural land is limited to around 4% of total, consisting of 18

provinces/cities comprising 148 districts. Laos population has 7,028,094 people and is equivalent to

0.09% of the total world population. Laos has a distinct rainy season from May to November,

followed by a dry season from December to April. Local tradition holds that there are three seasons

(rainy, cold and hot) as the latter two months of the climatologically defined dry season are

noticeably hotter than the earlier four months. Goats are increasingly important for subsistence food

production with over 90% of the global goat population found in developing countries (Glimp,

1995; FAO, 2005; World Bank, 2013). As goats produce several livestock products with lower

inputs than cattle and buffalo, smallholder goat farmers in developing countries, particularly in Asia

and Africa, have increasingly been recruited to goat raising, with goats described as an ‘entry point’

on the ‘pathway from poverty’. Goats are considered more easily managed than cattle, especially by

resource poor farmers, including women. Goat raising offers households nutritional benefits as meat

protein for hunger alleviation, enhanced livelihoods from animal trading income, more effective

utilisation of family labour, and increased livelihood stability and resilience in rural communities

due to more self-reliance (FAO, 2005; World Bank, 2013). In Southeast Asia, goats have been of

increasing importance, particularly in countries with large Islamic populations, including Indonesia,

Malaysia, and parts of the Philippines and Thailand. However, in recent years, increasing demand

for consumption of goat meat in Vietnam and China has created opportunities for increasing

production in the Lao People’s Democratic Republic (Laos, henceforth). Currently, the government

of Laos is attempting to obtain an average meat supply for local consumption of 60kg/capita/year,

plus increased meat exports to a value of USD 50 million by 2020 (FAO, 2005). In Laos, goat

production is traditionally extensive with low inputs, and subsequently low outputs (Kounnavongsa

et al., 2010). Four major goat management systems have been described, including: free range;

semi-free range; semi-rotational grazing; and permanent grazing with or without tethering. Free

range is the most commonly observed system, although semi-free range can be found in areas where

cropping predominates (Kounnavongsa et al., 2010; Phengvichith and Preston, 2011). In most

systems, goats are herded back to the village and kept in small hutches overnight for protection,

although housing is only considered beneficial if it is kept clean (Phengsavanh, 2003). The system

used by an individual farmer will depend upon feed and labour availability plus local community

agreements, particularly related to cropping and use of common grazing areas (Kounnavongsa et al.,

2010; Phengvichith and Preston, 2011). Typically, Lao goat herds consist of 3-10 animals

(Kounnavongsa et al., 2010; Phengvichith and Preston, 2011), although there are some recent

examples of developing herds with as many as 200 animals raised on semi- and fully-commercial

farms. Approximately 551,153 goats were recorded in Laos in the 2016 agricultural census (DLF,

2016). This number is likely to be underestimated, as it is widely considered to have been

increasing rapidly due to recent expanding regional demand for goat meat, particularly from

Vietnam, with estimates that between 2,000-3,000 goats per month are being exported. Increasing

demand for consumption of goat meat in Laos and neighbouring Vietnam and China, is providing

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opportunities for smallholder farmers to increase productivity and has led to the development of

semi to full commercial production systems to capitalise on the growth in this emerging livestock

sector, particularly if biosecure transboundary trade can be enhanced (Stur et al., 2002; Windsor,

2011; Nampanya et al., 2015). However, introducing goats and expanding small goat herds where

smallholders and potential commercial operators have limited experience of small ruminants can be

exceedingly challenging. In recent years, many international development agencies have promoted

smallholder goat-raising programs with distribution of goats to untrained farmers, often

accompanied by severe mortality and morbidity problems (Windsor et al., 2017). In developing

improved systems for feeding livestock, account must also be taken of the impacts on the

environment. It is estimated that livestock presently account for some 18% of greenhouses gases

which cause global warming (Steinfeld et al., 2006). Enteric methane from fermentative rumen

digestion is the main source of these emissions. There is an urgent need to develop ways of

reducing methane emissions from ruminants in order to meet future targets for mitigating global

warming. The legume tree Bauhinia acuminata is widely distributed in many parts of Laos

specially in Luang Prabang, and it has been observed that the foliage is readily consumed by goats.

The leaves of Bauhinia acuminata have 14.5% of protein of low solubility (22%). As is the case

with foliage from most legume trees, it contains many secondary plant compounds including

tannins (Silivong and Preston, 2015). Water spinach (Ipomoea aquatica) is cultivated for human

food and also is fed to animals such as goats, pigs, ducks and rabbits. It does not appear to contain

anti-nutritional compounds and has been used successfully for goats as the only source of

supplementary protein (Phongpanith et al; 2013). It grows equally well in water or in soil. It

responds dramatically in biomass yield and protein content when fertilized. (Preston et al., 2013)

reported that the leaves contain 24% protein in dry matter (DM) and that the protein is highly

soluble (71%) and therefore easily fermentable as a source of nutrients for rumen microorganisms.

These qualities make water spinach an ideal supplement for tree foliages of low nutritive value.

Thus, (Kongmanila et al., 2007) reported that water spinach supplementation of foliages from Fig,

Jujube and Mango trees increased the DM and crude protein intake of goats, and improved the

apparent digestibility and N retention. According to Thu Hong et al., 2011, the live weight gain of

goats fed Mimosa foliage was increased 27% by supplementing with fresh water spinach. Goats fed

a sole diet of cassava foliage also responded with increased DM digestibility and N retention when

fresh water spinach was provided as a supplement (Patshoummalangsy and Preston, 2006).

Cassava (Manihot esculenta Crantz) is an annual crop grown widely in the tropical and

subtropical regions. Roots of cassava are rich in energy (75 to 85% of soluble carbohydrate) but

with minimal levels of crude protein (2 to 3% in DM). The development of the starch industry in

Lao for export to China and other neighboring countries has increased the market for cassava roots.

As a result, cassava is currently the third most important crop in Laos, after rice and maize. The

varieties used for industrial starch production are known as “bitter” varieties due to the high content

of cyanogenic glucosides that are converted into the highly toxic hydrocyanic acid when consumed

by animals and people. The cassava varieties that are planted for human consumption are known as

“sweet” varieties as they have a lower content of cyanogenic glucosides. For every tonne of roots

that are harvested there are an additional 600kg of stems and leaves. However, the farmers in the

cassava factory area have no experience in the utilization of cassava leaves as the protein

supplement to feed to animals, especially cattle. The foliage of cassava has been shown to be an

3

effective source of bypass protein for fattening steers (Ffoulkes and Preston, 1978; Keo Sath et al.,

2008; Wanapat et al., 1997). It is thus a logical forage to provide the additional protein required in

diets rich in carbohydrate but low in protein. Cassava leaves are known to contain variable levels of

condensed tannins; about 3% in DM according to Netpana et al., 2001 and Bui Phan Thu Hang and

Ledin, 2005. Condensed tannins are reported to decrease rumen methane production and increase

the efficiency of microbial protein synthesis (Makkar et al., 1995; Grainger et al., 2009). Reductions

of CH4 production of 13 to 16% have been reported (Carulla et al., 2005; Waghorn et al., 2002,

Grainger et al., 2009; Woodward et al., 2004), apparently through a direct toxic effect on

methanogens. Brewers’ grains is a byproduct derived from the industrial brewing of beer. Research

with goats (Sina et al; 2017) highlighted a major interaction between the effect of the

supplementary brewers’ grains and the nature of the basal diet. The improvement in growth rate due

to addition of brewers’ grains was 130% when the basal diet was fresh cassava foliage but only

30% when the basal diet was water spinach (Sina et al., 2017). A positive approach to the problem

of how to reduce methane emissions from live stock has been to incorporate a low level (1%) of

biochar in the diet (Sangkhom et al., 2012; Leng et al., 2012a,b,c). Biochar is the product of

incomplete carbonization of fibrous biomass at high temperatures (Lehmann and Joseph, 2009). It is

a highly porous material which gives it valuable properties as a support mechanism for biofilms that

facilitate the adsorption of consortia of micro-organisms and nutrients that may prioritize

incorporation of hydrogen into volatile acids rather than methane (Leng, 2018 personal

communication).

2. THE OBJECTIVES

The study aimed at the utilization of locally available feed resources for increasing growth

performance and reducing enteric methane emissions from goats in Lao PDR. The specific

objectives were following: (i) To evaluate the of water spinach as a source of high soluble protein

and biochar on methane production in an in vitro system with substrate of Bauhinia acuminata or

Guazuma ulmifolia leaves; (ii) To evaluate the effect of water spinach as a source of high soluble

protein and biochar on feed intake, digestibility, N retention, methane emission and growth

performance of goats fed Bauhinia acuminata foliages plus molasses or dried cassava root chip as

the basal diets; (iii) To examine the effect of replacing water spinach by cassava foliage and/or

brewer’s grain on feed intake, digestibility, N retention and growth performance of goat fed

Bauhinia acuminata plus dried cassava root chip as the basal diets; (iv) To compare the sweet or

bitter of cassava leaves and biochar on gas production, methane content of the gas and methane

ml/g DM digested in an in vitro incubation.

3. THE HYPOTHESIS

(i) Water spinach, with its high content of soluble protein, would increase the rate of

fermentation and production of methane when added to forage rich in insoluble protein such as

Bauhinia acuminata or Guazuma ulmifolia leaves; (ii) The performance of growing goats fed

Bauhinia acuminata as the basal diet would be improved by supplementation with water spinach as

a rapidly fermentable protein source. Enteric methane production would be reduced by adding a low

level (1%) of biochar; (iii) Goats fed foliage of the legume tree Bauhinia acuminata would respond

positively in growth rate and feed conversion to a low-level supplement of brewers’ grains, and that

the degree of response would be greater when cassava foliage, rather than water spinach, was the

4

complementary source of protein; (iv) The methane content of the gas produced in an in vitro

fermentation would be reduced when leaves of bitter cassava replaced leaves of sweet cassava as

supplementary protein source and when 1% of biochar was added to the substrate.

4. SIGNIFICANT/INNOVATION OF THE DISSERTATION

This is the first series of study and the first sciencetific information on improving the

utilization of Bauhinia acuminata for goat production in Laos. The results presented in this

dissertation indicate that: (1) Goats fed Bauhinia acuminata responded with improved diet

digestibility, N retention and growth rate when the Bauhinia acuminata was supplemented with

water spinach; (2) But an important negative effect was that the improvement in diet digestibility by

supplementation with water spinach led to increases in methane production per unit diet DM

digested; (3) Supplementing Bauhinia acuminata foliage with leaves from a bitter variety of

cassava reduced the in vitro production of methane when compared with supplementation by leaves

from a sweet variety of cassava; (4) Ensiled brewers’ grains fed as an additive (5% as DM) to a diet

of Bauhinia acuminata improved the digestibility, N retention and growth rate of goats. The degree

of improvement was greater when the Bauhinia acuminata was supplemented with cassava foliage

instead of water spinach; (5) Biochar fed at 1% of a diet of Bauhinia acuminata and cassava foliage

was as effective as brewers’ grains in improving the growth rate of the goats.

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CHAPTER 1: LITERATURE REVIEW

There are main points following (i) Goat production in Laos; (ii) Role of goat production in

Laos; (iii) Goat nutrient and methane emission; (iv) Local available feed resources for goat in Laos.

CHAPTER 2: EFFECT OF WATER SPINACH ON METHANE PRODUCTION IN AN IN

VITRO INCUBATION WITH SUBSTRATES OF BAUHINIA ACUMINATA OR GUAZUMA

ULMIFOLIA LEAVES AND MOLASSES

INTRODUCTION

The greenhouse gases (GHG) emissions from the agriculture sector account for about 25.5%

of total global radiative forcing and over 60% of anthropogenic sources (FAO 2009). Animal

husbandry accounts for 18% of GHG emissions. Emission of methane (CH4) is responsible for

nearly as much radiative forcing as all other non-CO2 GHG gases combined (Beauchemin and

McGinn 2005). While atmospheric concentrations of GHGs have risen by about 39% since pre-

industrial era, CH4 concentration has more than doubled during this period (WHO, 2009). Reducing

GHG emissions from agriculture, especially from livestock, should therefore be a top priority since

it could curb global warming fairly rapidly (Sejian et al., 2010). Ruminants, such as cattle, buffalo,

sheep and goats, are the major contributors of total methane agricultural emissions (Leng, 1993;

Lassey, 2007; Chhabra et al., 2009). In ruminants, the H2 produced in rumen fermentation is

normally removed by the reduction of CO2 to methane. There is a need to develop feeding systems

for ruminants that will result in reduced emissions of methane gas from the enteric fermentation in

these animals. Previous research showed that methane production was less when fish meal rather

than groundnut meal was the substrate (Preston et al., 2013). The differences in methane production

appeared to be related to the solubility of the protein which was 16% in fish meal compared with

70% in groundnut meal. A similar finding was reported by Silivong and Preston (2015) who

showed that addition of water spinach to the substrate in an in vitro rumen fermentation increased

the rate of gas production and methane content in the gas. The protein in the water spinach was

highly soluble (66%). The hypothesis that underlined the present study was that water spinach, with

its high content of soluble protein, would increase the rate of fermentation and production of

methane when added to forages-rich in insoluble protein.

MATERIALS AND METHODS

Treatments and experimental design

The experimental design was a 2×4 factorial arrangement of 8 treatments with four

replications. The factors were:

- Foliage source: Bauhinia acuminata and Guazuma ulmifolia (BA and GU)

- Level of water spinach: 0, 5, 15 and 25% in substrate DM

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Preparation of substrate and the in vitro system

The in vitro system used recycled “PET” plastic bottles as flasks for the incubation and gas

collection. A simple in vitro system was used with recycled plastic bottles as flasks for the

incubation and gas collection (Diagram 1).

a. Water bath

b. Fermentation bottle (1.5liters)

c. Water storage reservoir (3liters)

d. Gas collection bottle (1.5liters)

Plastic tube (id: 4mm)

Diagram 1. A schematic view of the in vitro system to measure gas production in an in vitro incubation

- B and D bottles (1.5 liters capacity)., C bottle (3liters capacity). The B bottle containing

the substrate for fermentation was connected to the D bottle by a plastic tube (4 mm diameter). The

D bottle was marked at 50ml intervals before being suspended in the C bottle containing water.

Clay was used to cover the stoppers of the plastic bottle and junction of stopper and plastic tube to

prevent leakage of gas. The leaves from Bauhinia and Quazuma, and leaves plus stems of water

spinach, were chopped into small pieces (3-5mm) and dried at 65°C for 48h then ground with a

coffee grinder, and mixed according to the proportions shown in Table 1. The mixtures (12g DM)

were put in the incubation bottle with 960 ml of buffer solution (Table 2) and 240 ml of rumen

fluid. The rumen fluid was taken at 3.00-4.00am from the slaughter house from a buffalo

immediately after the animal was killed. A representative sample of the rumen contents (including

feed residues) was put in a vacuum flask and taken to the laboratory, and stored until 5.00am, when

the contents were filtered through a layer of cloth before being added to the incubation bottle. The

remaining air in the flask was flushed out with carbon dioxide. The bottles were incubated at 38°C

in a water bath for 24 h.

Table 1. Composition of diets (% DM basis)

BA#GU BA#GU-WS 5 BA#GU-WS 15 BA#GU-WS 25

Leaf meal# 80 75 65 55

Water spinach 0 5 15 25

Molasses 20 20 20 20

Total 100 100 100 100

# Bauhinia or Guazuma leaf meals

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Table 2. Ingredients of the buffer solution (g/liter)

CaCl2 NaHPO4.12H2O NaCl Cl MgSO4.7H2O NaHCO3 Cysteine

0.04 9.30 0.47 0.57 0.12 9.80 0.25

Source: Tilly and Terry (1963)

Data collection and measurements

Gas production was measured at 4 intervals for 6, 12, 18 and 24h by water displacement (a

calibrated recycled water bottle with the bottom removed) and at the end of each incubation, the

methane concentration in the gas was measured with a Crowcon infra-red analyser (Crowcon

Instruments Ltd, UK). Residual DM in the incubation bottle was determined by filtering the

incubation residues through cloth to estimate DM loss during incubation and drying the residue

(65°C for 72h).

Chemical analyses

The samples of foliage, water spinach and residual substrate were analysed for DM, ash and

N according to AOAC (1990) methods. Solubility of the protein in the leaves was determined by

shaking 3g of dry leaf meal in 100 ml of M NaCl for 3h then filtering through Whatman No.4 filter

paper, and determining the N content of the filtrate (Whitelaw et al., 1963).

Statiscal analysis

The data were analyzed by the general linear model option of the ANOVA program in the

Minitab software (Minitab, 2014). In the model the sources of variation were: treatments, replicates

and error.

The statistical model was: Yijk = μ + Pi + Aj + Pi*Aj+ eijk

Where: Yijk is dependent variables., μ is overall mean., Pi is the effect of foliage source

Aj is the effect of level of water spinach., (P*A) ij is the interaction between source of foliage

and source of level of water spinach and eijk is random error

RESULTS

Chemical composition

Percentages of crude protein, ash and protein solubility were higher in water spinach than in

Bauhinia acuminata and Guazuma ulmifolia leaves, but DM was lower. The protein content and

solubility in the leaves of Guazuma ulmifolia were higher than in Bauhinia acuminata, but ash was

lower (Table 3).

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Table 3. The chemical composition of feed (% in DM, except DM which is on fresh basis)

DM N*6.25 Ash Protein solubility Tannin NDF ADF

Bauhinia leaves 40.0 15.0 21.2 23.7 1.1 43.7 32.4

Bauhinia stem 38.1 12.3 4.29 - 42.7 31.5

Guazuma ulmifolia 36.0 18.4 3.9 33.3 -

Water spinach 10.6 18.5 9.7 66.4 42.3 33.3

Molasses 80.4 5.4 10.5

Source: Silivong et al., 2018

Values for the gas production, percent methane in the gas and methane produced per unit

substrate solubilized increased with length of incubation time (Table 4). Gas production and percent

substrate solubilized were increased by increasing the level of water spinach in the substrate, and

were higher for Guazuma ulmifolia than Bauhinia acuminata at each incubation interval.

Table 4. Mean values for gas production, percentage of methane in the gas, methane production (ml), DM solubilized and

methane production per unit DM solubilized according to leaf source (Bauhinia and Guazuma) and level of water spinach

Foliage

source p

Level of water spinach (%)

p SEM

Interaction

BA GU WS-0 WS-5 WS-15 WS-25 SEM P

0-6 hr

Gas production, ml 363 483 <0.001 286d 354c 476b 575a <0.001 5.1 7.2 0.574

Methane, % 8.8 9.9 <0.001 7.6d 8.9c 9.6bc 11.4a <0.001 0.2 0.2 0.673

DM solubilized, % 53.1 56.3 <0.001 49.2d 53.8c 56.4b 59.4a 0.001 0.2 0.3 0.753

Methane, ml/g DM

solubilized 5.1 7.2 <0.001 3.7d 4.9c 6.8b 9.2a <0.001 0.2 0.2 0.665

0-12 hr


Methane, % 13.8 15.9 <0.001 11.1d 13.6c 15.1bc 19.6a <0.001 0.3 0.4 0.563

DM solubilized, % 56.5 60.2 <0.001 53.2d 57.1c 59.9b 63.2a <0.001 0.3 0.5 0.756

Methane, ml/g DM


0-18 hr


9

Methane, % 18.9 21.8 <0.001 16.3d 19.5c 21.3b 24.3a <0.001 0.2 0.3 0.675

DM solubilized, % 59.4 63.5 <0.001 56.1d 60.1c 62.4bc 67.0a <0.001 0.4 0.6 0.872

Methane, ml/g DM


0-24 hr


Methane, % 24.4 27.9 <0.001 20.4d 24.8c 27.9b 31.5a <0.001 0.2 0.3 0.832

DM solubilized, % 61.8 67.3 <0.001 59.0d 64.3c 65.2bc 69.6a <0.001 0.4 0.6 0.742

Methane, ml/g DM


abc Mean values without common superscript differ at p<0.05, BA: Bauhinia acuminata, GU: Guazuma

ulmifolia, P: Probability value, WS: Water spinach

DISCUSSION

The increases in methane concentration in the gas and per unit DM solubilized, with

incubation interval, are similar to the findings reported by Outhen et al., 2011, Binh Phuong et al .,

2011) and Silivong and Preston, 2015. This is thought to be due to methane being increasingly

produced by secondary fermentation from acetate (Inthapanya et al., 2011) as the incubation

interval increased. The increases in methane production with increasing proportions of water

spinach in the substrate, and the higher methane production for treatments with Guazuma ulmifolia

leaves compared with Bauhinia acuminata leaves, were closely related to the degree of solubility of

the protein in these different combinations of substrate (Table 3). . A similar finding was reported

by Inthapanya and Preston, 2014 when cassava leaves (protein solubility 25.6%) replaced water

spinach (protein solubility 66.3%) in an in vitro incubation of urea-treated rice straw. It is not

possible to differentiate between the direct effects of increased protein solubility per and the indirect

effect of reducing the concentrations and the level of anti-nutritional factors (eg: condensed tannins)

in the substrate (Table 3) when Bauhinia acuminata was replaced by Guazuma ulmifolia, and the

level of water spinach was increased. The positive role of tannins in reducing the activity of

methanogenic bacteria has been reported by several researchers (Goel and Makkar, 2012; Soltan et

al., 2012).

CONCLUSIONS

- Increasing the length of the incubation in the in vitro rumen fermentation of leaves of

Bauhinia acuminata and Guazuma ulmifolia increased gas production, methane concentration in the

gas and methane produced per unit substrate solubilized.

- Supplementation with water spinach increased the rate of gas production, the percentage

DM solubilized, and the methane concentration in the gas and methane produced per unit substrate

solubilized on both sources of leaves.

- Gas production, methane concentration in the gas and methane produced per unit substrate

solubilized were higher when leaves of Guazuma ulmifolia replaced those from Bauhinia

acuminata.

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CHAPTER 3:

EFFECTS OF WATER SPINACH AND BIOCHAR ON METHANE EMISSIONS AND

GROWTH PERFORMANCE OF GOAT FED BAUHINIA ACUMINATA AND MOLASSES

OR CASSAVA ROOT CHIPS AS THE BASAL DIET

INTRODUCTION

Livestock are the most important source of protein food and family cash income of farmers

in Laos, and also give manure for cropping in the rural areas. Most of the production from livestock

such as goats, cattle, pigs and poultry comes from smallholders using traditional management

systems. The main feed resources for ruminants are native grasses, legumes and tree leaves that are

available in the natural grassland and forests (Phengsavanh, 2003). The conventional feeding

system for goats in Lao PDR is based mainly on the use of natural grasses. However, in the dry

season, natural pasture decreases in nutritive value and improved grasses cannot grow. Therefore, it

is important to find an alternative feeding system because purchased supplements are too expensive

for poor farmers. On the other hand, there are many trees and shrubs available. Preston and Leng,

2009 and Leng, 1997 have emphasized that in tropical countries one of the most appropriate ways

to improve feed supplies for ruminants is through utilization of tree and shrub foliages. The

negative feature of livestock is that they contribute some 18% of the greenhouse gases that are

causing global warming (Steinfeld et al., 2006). Enteric methane from fermentative digestion is the

main source of these emissions. Thus when new or modified feeding systems are being researched

the effects of these changes on enteric methane emissions should be monitored, in view of the need

to reduce methane emissions so as to meet future targets for mitigating global warming. The legume

tree Bauhinia acuminata is widely distributed in the Luang Prabang Province and it has been

observed that the foliage is readily consumed by goats. The leaves of Bauhinia acuminata have

14.5% of protein of low solubility (22%). As is the case with most foliage from legume trees, it

contains many secondary plant compounds including tannins (Queiroz Siqueira et al., 2012). The

low solubility of the crude protein in Bauhinia acuminata is indicative of the binding action of

tannins on this nutrient source (Silivong and Preston, 2015). Daovy et al., 2007 reported that water

spinach (Ipomoea aquatica) supplementation of low quality tree foliage (from Fig, Jujube and

Mango trees) increased the DM and crude protein intake of goats, and improved the apparent

digestibility and N retention. According to Thu Hong et al., 2011, the live weight gain of goats fed

Mimosa foliage was increased by supplementing with fresh water spinach at 27% of the total DM

intake. Goats fed a sole diet of cassava foliage also responded ith increased DM digestibility and N

retention when fresh water spinach was provided as a supplement (Pathoummalangsy and Preston,

2006). Molasses is a source of highly fermentable carbohydrate (contains > 50% soluble sugars)

and is very low in crude protein “<0.5% in DM” (Ffoulkes and Preston, 1978). Cassava roots have

high levels of energy (75 to 85% of soluble carbohydrate) and minimal levels of crude protein (2 to

3% CP); they have been used as a source of readily-fermentable energy (Kang et al., 2015;

Polyorach et al., 2013; Wanapat et al., 2013a,b). A positive approach to the problem of how to

reduce methane emissions from live stock has been to incorporate a low level (1%) of biochar in the

diet (Sangkhom et al., 2012; Leng et al., 2012a,b,c). Biochar is the product of incomplete

carbonization of fibrous biomass at high temperatures (Lehmann and Joseph, 2009). It is a highly

11

porous material which gives it valuable properties as a support mechanism for biofilms that may

facilitate the adsorption of consortia of micro-organisms and nutrients (Leng, 2014). In the research

reported here, it was hypothesized that: (i) the performance of growing goats fed Bauhinia

acuminata and molasses or cassava root chip as the basal diet would be improved by

supplementation with water spinach as a rapidly fermentable protein source; and (ii) that

incorporation of a low level of biochar in the diet might reduce enteric methane emissions.



The experimental plan was a 2×2 factorial arrangement in a Randomized Completely Block

Design (RCBD) with 4 treatments and there were 4 replications of the experiment 2 and 3

replications of the experiment 3.

The factors applied to a basal diet of fresh Bauhinia acuminata foliage were:

- With or without water spinach (WS and No-WS)

- With or without biochar (BC and No-BC)

Individual treatments were:

- BA = Bauhinia acuminata ad libitum

- BABC = Bauhinia acuminata ad libitum + 1% biochar on DM intake

- BAWS = 70% Bauhinia acuminata and 30% water spinach on DM basis

- BAWSBC = 70% Bauhinia acuminata and 30% water spinach + 1% biochar

Biochar was given 1% on DM intake

+ In the experiment 2: Molasses diluted with fresh water by ratio of 1:9 (1 kg of molasses

and 9 litters of fresh water) and was used as the carrier for the biochar and was given ad libitum on

all diets., In the experiment 3: Sun-dried cassava root chips were used as the carrier for the biochar.

The biochar was mixed with finely-chopped, sun-dried cassava root chips (20% biochar: 80% sun-

dried cassava root chips) which were fed at 5% of the diet (DM basis) once daily at 7.00am.

Animals and housing

- Experiment 2: Sixteen local weaned goats with initial average body weight of

11.65±3.95kg and 5-6 months of age were used. They included 4 males (non-castrated) and 12

females. These animals were purchased from Phoukhoun District LaungPrabang Province.,

Experiment 3: Twelve weaned goats (local breed) with initial average body weight of 12.1±3.7kg

and 5-6 months of age were used. They included 8 males (non-castrated) and 4 females. These

animals were purchased from Chomphet District Laungprabang Province. In both studies, goats

were housed individual pens and made from local material such as: bamboo (dimensions of width

1 m, length 1 m and height 0.9 m) and designed to collect separately feces and urine. They were

vaccinated against Pasteurellosis, foot and mouth disease and treated with Ivermectin (1ml/20 kg

live weight) to control internal and external parasites. They were adapted to the pens and the

feeds for 10 days before starting the experiment. The experiment lasted 100 days, including the

adaptation period.

12

Feed and management

Molases were purchased from Vientiane Province, cassava root was purchased from farmers

around the Luangprabang District, chopped into small pieces and exposed to sunlight for 48 hours

to reduce the moisture to about 15%, Foliages of Bauhinia acuminata and water spinach were

collected daily from natural stands in the University campus. The biochar was produced by burning

rice husks in a top lit updraft (TLUD) gasifier stove (Olivier, 2010). It was ground to a particle size

that passes through a 1 mm sieve. The foliages were offered twice daily at 07:30 and 16:00h by

hanging in bunches above the feed trough.

Data collection and measurement

- Experiment 2: Live weight was recorded in the morning before feeding at the beginning

and at the end of the experiment and at intervals of 10 days during the experiment. Quantities of

feed offered and refused were recorded daily. Every 10 days, samples were taken for analysis of

DM and N. Samples of Bauhinia acuminata foliage offered and residues were separated into stem

and leaves (containing attached petioles). Representative samples of each component were analyzed

for DM, N and ash. Samples of rumen fluid were taken by stomach tube 2h after morning feeding

on the last day of the experiment. The pH value was measured immediately with a portable digital

pH meter. A drop of concentrated sulphuric acid was added prior to determination of ammonia by

steam distillation. Digestibility and N retention were recorded four times, over 5 days periods at 20

day intervals (after 20, 40, 60 and 80 days). In each collection period, samples of feeds offered and

refused were taken daily and bulked for the 5 days of each period. Urine was collected in buckets

containing 20ml of a solution of sulphuric acid (10% sulphuric acid concentrate + 90% distilled

water). Feces were collected daily and stored in the refrigerator at 4-8ºC and at the end of each

period, sub-samples were mixed together and ground with a coffee grinder. Samples of eructed

gases were measured on the last day of the experiment, in the morning 2h after feeding. The goats

were placed in a plastic-covered cage and after a period of 10 minutes for equilibration with the

surrounding air, the concentrations of methane and carbon dioxide were recorded over a 10 minute

period, using a GASMET 4030 meter (Gasmet Technologies Oy, Pulttitie 8A, FI-00880 Helsinki,

Finland)., Experiment 3: Live weight was recorded in the morning before feeding at the beginning

and at the end of the experiment and at intervals of 10 days during the experiment. Quantities of

feed offered and refused were recorded daily. Every 10 days, samples were taken for analysis of

DM and N. Samples of Bauhinia acuminata foliage offered and residues were separated into stem

and leaves (containing attached petioles). Representative samples of each component were analyzed

for DM, N and ash. Samples of rumen fluid were taken by stomach tube 2h after morning feeding

on the last day of the experiment. The pH value was measured immediately with a portable digital

pH meter. A drop of concentrated sulphuric acid was added prior to determination of ammonia by

steam distillation. Digestibility and N retention were recorded three times, over 5 day periods at 30

day intervals (after 30, 60 and 90 days). In each collection period, samples of feeds offered and

refused were taken daily and bulked for the 5 days of each period. Urine was collected in buckets

containing 20ml of a solution of sulphuric acid (10% sulphuric acid concentrate + 90% distilled

water). Feces were collected daily and stored in the refrigerator at 4-8ºC and at the end of each

period, sub-samples were mixed together and ground with a coffee grinder.

13

Chemical analyses

The sub-samples of feces and of feeds offered and refused were analysed for DM, N and ash

according to AOAC (1990) methods. Urine was analysed for nitrogen (AOAC 1990). Solubility of

the protein in the leaves was determined by shaking 3g of dry leaf meal in 100 ml of M NaCl for 3h

then filtering through Whatman No.4 filter paper, and determining the N content of the filtrate

(Whitelaw et al., 1963).

Statistical analysis

The data were analysed statistically as a Randomize Complete Block Design (RCBD) by

variance analysis (ANOVA) using the general linear model (GLM) procedure of Minitab software

version 16.0 (Minitab, 2014). The treatment least square means showing significant at difference at

the probability level of P<0.05 were compared Turkey’s pair wise comparison procedure.

The statistical model used in the experiments 2 and 3:

- Growth study was:

Yijk = μ + Bk+ Pi + Aj + Pi*Aj+ eijk

Where: Yijk is dependent variables., μ is overall mean., Bk is the effect of live weight., Pi is

the effect of protein source., Aj is the effect of biochar source., (P*A) ij is the interaction between

source of protein and source of biochar and eijk is random error

- Digestibility study was:

Yijk = μ + Ti + Pj +Ak + eijk

In where, Yijk = Dependent variables., μ = Overall mean., Ti = Treatment effect (i=1-4).,

Pj = Column effect (j=1-4)., Ak = Row effect (k=1-4) and eijk = Random error

The relationship between N intake and N retention was developed by regression analyses.

The best model was selected based on adjusted R2.

The methane to carbon dioxide ratios were used to calculate the reduction of methane

production according to the formula proposed by Madsen et al., 2010:

Ratio CH4/CO2 = (a-b)/(c-d)

Where "a" is methane concentration in mixed eructed gas plus air., "c" is carbon dioxide

concentration in mixed eructed gas plus air., "b" is methane in the air in the goat shed., "d" the

carbon dioxide in goat shed air

The relationship between N intake and N retention was developed by regression analyses.

The best model was selected based on adjusted R2.

RESULTS


The concentrations of crude protein and ash and the solubility of the protein were lower, and

of DM were higher, in Bauhinia acuminata than in water spinach (Table 1).

14

Table 1. Chemical composition of dietary ingredients (% in DM, except DM which is on fresh basis)


Bauhinia leaves 40.0 15.0 21.2 23.7 1.1 43.7 32.4

Bauhinia stem 38.1 12.3 4.29 - 42.7 31.5

Water spinach 8.16 18.3 9.74 69.4 42.3 33.3

Molasses 80.4 5.4 10.5

Cassava root chips 82.4 2.81 2.23 - - -

Biochar - - 38.3 - - -

Source: Silivong et al., 2018

- Experiment 2:

Feed intake, growth rate and feed conversion

DM intake expressed as a percentage of live weight was not affected by supplementation

with biochar or water spinach (Table 2).

Table 2. Mean values of feed intake by goats fed Bauhinia acuminata supplemented with water spinach (WS)

or biochar (BC) or not supplemented

PS

p

BCS

P SEM

Interaction

WS No-WS BC No-BC SEM p

DM intake, g/d

Molasses 213 224 0.004 218 219 0.67 2.52 14.4 0.369

Bauhinia 149 229 <0.001 164 214 <0.001 3.07 35.69 0.719

Water spinach 161 0 <0.001 82.0 79.2 0.025 0.87 6.25 0.683

Biochar 2.47 2.85 <0.001 5.31 0 <0.001 0.03 0.4 1 0.371

Total 526 455 <0.001 469 512 <0.001 3.77 47.67 0.558

Per kg LW 32.9 33.1 0.21 32.8 33.2 0.016 0.13 0.6 0.923

N*6.25, % in DM 12.5 10.3 11.5 11.5

BC: Biochar, BCS: Biochar source, d: day, g gram, Kg: Kilogram, LW: live weight, P: Probability

value, PS: Protein source, SEM: Standard error of the mean with dferror: 9, WS: Water spinach.

15

Daily live weight gain and feed conversion were improved by feeding water spinach and by

supplementation with biochar (Table 3). There was a close relationship between live weight gain

and feed conversion ratio.

Table 3. Mean values for live weight, live weight change, feed DM intake and DM feed conversion for goats

fed a basal diet of Bauhinia acuminata foliage and molasses

PS

p

BCS

p SEM

Interaction


Live weight, kg

In wt, kg 12.9 12.2 0.598 11.8 13.3 0.263 0.87 1.22 0.571

Fin wt, kg 18.6 15.3 0.019 16.5 17.4 0.495 0.87 1.22 0.382

LWG, g/d 51.4 28.7 <0.001 43.7 36.5 0.047 2.32 3.28 0.543

DMI, g/d 526 455 <0.001 469 512 <0.001 3.77 47.67 0.558

FCR, g/g 10.7 16.2 0.014 11.4 15.5 0.055 1.34 1.90 0.580

BC: Biochar, BCS: Biochar source, DMI: DM intake, FCR: DM feed conversion, Fin wt: Final

weight, In wt: Initial weight, Kg: Kilogram, LWG: Live weight gain, P: Probability value, PS: Protein

source, SEM: Standard error of the mean with dferror: 9, WS: Water spinach.

Apparent digestibility and N retention

Supplementing the basal diet of Bauhinia acuminata and molasses with water spinach

increased the apparent digestibility of DM, OM and crude protein, but there were no differences due

to biochar (Table 4). Daily N retention, N retention as percent of N intake and of N digested were

all improved by supplementation with water spinach. There was a tendency for biochar to improve

daily N retention (p=0.082) and this effect was significant when N retention was expressed as a

percent of N intake or of N digested.

Table 4. Mean values of apparent digestibility and N balance in goats fed Bauhinia acuminata and molasses

supplemented with water spinach (WS) and biochar (BC) or not supplemented (No-WS; No-BC)

PS

p

BCS

p SEM

Interaction


Apparent digestibility, %

DM 72.0 64.5 <0.001 69.1 67.5 0.100 0.68 1.68 0843

OM 75.0 67.4 <0.001 71.5 70.9 0.579 0.74 2.10 0.591

N*6.25 69.2 43.8 <0.001 55.0 57.9 0.294 1.98 6.48 0.502

16

N balance, g/day

Intake 11.1 7.0 <0.001 8.8 9.3 0.296 0.32 1.04 0.502

Feces 3.2 2.3 <0.001 2.5 3.0 0.021 0.16 0.53 0.583

Urine 1.8 1.4 <0.001 1.4 1.8 0.007 0.09 0.29 0.371

Retention 6.1 3.4 <0.001 4.9 4.5 0.082 0.16 0.41 0.719

N retention as:

% N intake 55.0 50.0 0.008 56.2 48.8 <0.001 1.32 3.73 0.324

% N digested 76.8 72.1 0.009 77.1 71.7 0.003 1.25 3.76 0.440

BC: Biochar, BCS: Biochar source, DM: Dry matter, Kg: Kilogram, N: Nitrogen, OM: Organic

matter, P: Probability value, PS: Protein source, SEM: Standard error of the mean with dferror: 9, WS: Water

spinach

Rumen ammonia, pH and methane to carbon dioxide ratio

Rumen pH did not differ among the diets (Table 5). Rumen ammonia, which was high on all

diets, was increased by supplementation with water spinach but was not affected by biochar.

Table 5. Mean values of rumen pH and ammonia, and ratio of methane to carbon dioxide in eructed breath

of goats fed Bauhinia acuminata and molasses supplemented with water spinach (WS) and biochar (BC) or

not supplemented (No-WS; No-BC)

PS

p

BCS

p SEM

Interaction


Rumen pH 7.08 7.03 0.465 7.04 7.06 0.756 0.05 0.063 0.727

NH3, mg/liter 397 298 <0.001 347 347 0.999 9.70 13.71 0.935

CH4:CO2 0.0211 0.0292 0.043 0.0243 0.0260 0.641 0.003 0.0036 0.800

BC: Biochar, BCS: Biochar source, CH4: Methane, CO2: Carbon dioxide, NH3: Ammonia, pH:

Percentage of hydrogen ion, P: Probability value, PS: Protein source, SEM: Standard error of the mean

with dferror: 9, WS: Water spinach.

The ratio of methane to carbon dioxide in eructed breath of the goats was lower in the

eructed breath of the goats supplemented with water spinach and not affected by supplementation

with biochar.

- Experiment 3:

Feed intake, growth rate and feed conversion

DM intake was increased 38% by supplementation with water spinach and by 5% from

feeding of biochar (Table 6).

17

Table 6. Mean values of feed intake by goats fed Bauhinia acuminata and cassava root chips supplemented

with water spinach (WS) or biochar (BC) or not supplemented

PS

p

BCS

p SEM

Interaction


DM intake, g/d

Cassava root chips 56.7 49.3 0.092 43.3 62.7 <0001 3.14 14.21 0.463

Bauhinia 350 335 0.009 361 325 <0.001 3.95 52.19 0.671

Water spinach 127 0

62.8 63.9 0.431 1.02 14.58 0.940

Biochar 2.76 3.05

5.81 0

0.38 0.478

Total 536 388 <0.001 472 451 0.009 5.81 60.01 0.572

Per kg LW 36.8 27.1 <0.001 31.8 32.2 0.244 0.26 1.79 0.609

N*6.25, % in DM 14.2 12.4 13.2 13.4

BC: Biochar, d day, BCS: Biochar source, g: gram, Kg: Kilogram, LW: Live weight, P: Probability

value, PS: Protein source, SEM: Standard error of the mean with dferror: 6, WS: Water spinach

Daily live weight gain was improved 120% by supplementation with water spinach and by

27% due to biochar (Table 7). Water spinach improved DM feed conversion by 27%. There was a

close relationship between live weight gain and feed conversion.

Table 7. Mean values for live weight, live weight change, feed DM intake and DM feed conversion for goats

fed a basal diet of Bauhinia acuminata foliage and Cassava root chips

PS

p

BCS

p SEM

Interaction


Live weight, kg

In wt, kg 12.0 12.9 0.579 12.6 12.3 0.813 1.06 1.5 0.669

Fin wt, kg 17.5 15.4 0.164 17.1 15.8 0.372 0.96 1.36 0.749

LWG, g/d 60.9 27.5 <0.001 49.4 39.0 0.002 1.64 2.33 0.304

DMI, g/d 536 388 <0.001 472 451 0.009 5.81 60.01 0.572

FCR, g/g 9.0 14.8 0.041 11.0 12.8 0.481 1.68 2.37 0.852

BC: Biochar, BCS: Biochar source, DMI: DM intake, d: day, FCR: DM feed conversion, Fin wt:

Final weight, g: Gram, In wt: Initial weight, Kg: kilogram, LWG: Live weight gain, P: Probability value, PS:

Protein source, SEM: Standard error of the mean with dferror: 6, WS: Water spinach

18

Apparent digestibility and N retention

Apparent digestibility coefficients were increased by water spinach supplement for DM, OM

and crude protein and by biochar for DM and OM (Table 8). Daily N retention and N retention as

percent of N intake and N digested were all improved by supplementation with water spinach and

biochar.

Table 8. Mean values of apparent digestibility and N balance in goats fed Bauhinia acuminata and cassava

root chips supplemented with water spinach (WS) and biochar (BC)or not supplemented (No-WS; No-BC)

PS

p

BCS

p SEM

Interaction



DM 71.3 63.2 <0.001 68.9 65.6 0.009 0.88 2.20 0.288

OM 74.3 67.1 <0.001 71.9 69.4 0.031 0.80 2.05 0.301

N*6.25 77.0 50.7 <0.001 66.0 61.6 0.217 2.48 9.18 0.762

N balance, g/day

Intake 12.3 8.1 <0.001 10.6 9.9 0.217 0.40 1.47 0.762

Feces 3.6 2.5 <0.001 2.9 3.1 0.020 0.08 0.17 0.078

Urine 2.2 1.8 0.008 2.0 2.1 0.740 0.10 0.34 0.525

Retention 6.5 3.8 <0.001 5.7 4.7 0.023 0.30 1.11 0.614

N retention as:

% N intake 52.0 45.1 <0.001 52.3 44.8 <0.001 1.32 4.56 0.424

% N igested 73.9 66.3 <0.001 73.0 67.2 <0.001 0.74 2.21 0.515

BC: Biochar, BCS: Biochar source, DM: Dry matter, N: Nitrogen, P: Probability value,

PS: Protein source, SEM: Standard error of the mean with dferror: 6, WS: Water spinach

pH and Rumen ammonia

The rumen pH was not affected by supplements of water spinach and biochar (Table 9).

Rumen ammonia was high for all diets and was increased by supplementation with water spinach,

but was not affected by biochar. There was a close relationship between live weight gain and rumen

ammonia concentration.

19

Table 9. Mean values of rumen pH and ammonia in goats fed Bauhinia acuminata and cassava root chips

supplemented with water spinach (WS) and biochar (BC) or not supplemented (No-WS; No-BC)

PS

p

BCS

p SEM

Interaction


Rumen pH 7.04 7.01 0.683 7.01 7.04 0.683 0.05 0.06 0.759

NH3, mg/liter 405 286 <0.001 354 337 0.422 14.17 24.04 0.975

BC: Biochar, BCS: Biochar source, mg: Milligram, NH3: Ammonia, P: Probability value, pH:

Percentage of hydrogen ion, PS: Protein source, SEM: Standard error of the mean with dferror: 6, WS: Water

spinach

DISCUSSION

The results of this experiment agree with the findings of: (i) Kongmanila et al., 2011 that

supplementation with water spinach increased the digestibility of Mango foliage growing goats; and

(ii) Phongpanith et al., 2013 who reported that water spinach supplementation increased the

digestibility and N retention of goats fed Muntingia foliage. Presumably the high solubility of the

protein in water spinach furnished amino acids and peptides required by micro-organisms for

efficient rumen digestion, and that these were limited in the Bauhina acuminata foliage because of

its low protein solubility. In contrast with the report by Leng et al., 2014, that biochar reduced

methane emission from cattle fed urea-treated rice straw, in the present experiment with goats fed

tree foliage there was no effect of biochar on methane emissions. However, in agreement with these

authors, the biochar had a positive effect on growth performance.

CONCLUSIONS

- Goats fed Bauhinia acuminata foliage and molasses or cassava root chip, supplemented

with water spinach, grew faster and had better DM feed conversion, and higher apparent

digestibility of DM and crude protein, and higher N retention, than goats fed only Bauhinia

acuminata foliage and molasses or cassava root chip, but were higher on daily gain and had better

DM feed conversion when goat fed Bauhinia acuminta and cassava root chips than Bauhinia

acuminata and molasses as the basal diet.

- The higher value of rumen ammonia in goats fed water spinach reflected the greater

solubility of the crude protein in the water spinach.

- Supplementing the basal diet of Bauhinia acuminata and molasses with water spinach led

to a reduction in the methane/carbon dioxide ratio in the eructed breath of the goats.

20

CHAPTER 4: EFFECT OF REPLACING WATER SPINACH (Ipomoea aquatic) BY

CASSAVA (Manihot esculenta Crantz) FOLIAGE AND/OR BREWER’S GRAINS ON FEED

INTAKE, DIGESTIBILITY, N RETENTION AND GROWTH PERFORMANCE IN GOAT

FED BAUHINIA ACUMINATA PLUS CASSAVA ROOT CHIPS AS THE BASAL DIET

INTRODUCTION

Research by Silivong and Preston (2015) showed that the growth rate of goats fed foliage of

the legume tree Bauhinia acuminata was increased by supplementation with fresh water spinach

and biochar. The protein in water spinach is very soluble (Silivong and Preston, 2015) and it is

thought that its role in improving the utilization of foliages of low digestibility, such as Bauhinia

acuminata, is because the water spinach acts as a source of readily available nitrogenous

compounds for rumen micro-organisms (Silivong and Preston 2015, 2016). The positive role of

biochar as a supplement in ruminant diets is thought to reflect another feature of ruminant nutrition,

namely as a support mechanism for biofilms that host consortia of micro-organisms facilitating the

utilization of nutrients with major benefits for the process of rumen fermentation (Leng, 2014). In

this role, it appears that biochar is acting as a “prebiotic”, by promoting synergism between

nutrients and micro-organisms in the animal’s digestive system. A similar synergism appears to be

the explanation for the beneficial effects on growth rates of cattle (Binh et al., 2017) and goats (Sina

et al., 2017) of small proportions in the diet of brewers’ grains, a byproduct derived from the

industrial brewing of beer. The research with goats (Sina et al., 2017) highlighted a major

interaction between the effect of the supplementary brewers’ grains and the nature of the basal diet.

The improvement in growth rate due to addition of brewers’ grains was 130% when the basal diet

was fresh cassava foliage but only 30% when the basal diet was water spinach (Sina et al., 2017).

The hypothesis that was tested in the present experiment was that goats fed foliage of the legume

tree Bauhinia acuminata would respond positively in growth rate and feed conversion to a

supplement of brewers’ grains, and that the degree of response would be greater when cassava

foliage, rather than water spinach, was the complementary source of protein.


Experimental treatments and design

The basal diet was fresh foliage from the legume tree Bauhinia acuminata fed ad

libitum, supplemented with biochar (1% of diet DM) and cassava root chips (4% of diet DM).

The treatments in a 2×2 factorial arrangement were:

Source of protein-rich foliage:

- 30% of DM feed intake (Water spinach: WS)

- 30% of DM feed intake (Cassava foliage: CF)

Supplementary brewers’ grains:

- 4% of DM feed intake (Brewer’s grains: BG)

- No supplement (No-BG)

21

In the digestibility study the design was a 4×4 Latin Square with 4 male goats and 4 periods

each of 12 days: 7 days for adaptation and 5 days for collection of feed refusals, feces and urine.

The goats (local breed) weighed 15.5±0.65 kg and were 5-6 months of age. They were purchased

from farmers around Luangprabang city. They were housed individually in metabolism cages made

from bamboo (dimensions of width 0.8 m, length 0.9 m and height 1 m), designed to collect

separately feces and urine. In the growth study the design was a Randomized Completely Block

Design (RCBD) with 4 replications of the two factors in a 2×2 factorial design, with sixteen goats

(balanced males and females) with initial body weight of 14.4 ± 1.45 kg and 5-6 months of age.

They were housed in individual pens made from wood and bamboo. In both studies, the goats were

vaccinated against Pasteurellosis and Foot and Mouth disease and were de-wormed before the start

of the experiment.

Feeding and management

In both studies: Foliages of Bauhinia acuminata and water spinach (Ipomoea aquatica) were

collected daily from natural stands in and around the University campus. Cassava (Manihot

esculenta Crantz) foliage was collected daily from a demonstration plot in the Department of

Animal Science Farm. Cassava root was harvested from the demonstration plot in the department of

Animal Science Farm. It was chopped into small pieces and exposed to sunlight for 48h to reduce

the moisture to about 15%. Brewers’ grains were purchased from a brewery in Vientiane city. The

biochar was produced by burning rice husks in a top lit updraft (TLUD) gasifier stove (Olivier,

2010). It was ground to a particle size that passes through a 1 mm sieve. The biochar was mixed

with the cassava root chips and fed from a plastic bucket. Bauhinia acuminata foliage, water

spinach and cassava foliage were hung in bunches above the feed trough. Fresh feeds were offered

twice daily at 07:30 and 16:00h. Water was freely available.

Measurements

Metabolism study

Live weight was recorded in the morning before feeding at the beginning and at the end of

each period. Feeds offered, and refusals were collected daily during the 5 days of the collection

period. Urine was collected in buckets with 20 ml of a solution of sulphuric acid to ensure a pH of

less than 4 (10% sulphuric acid concentrate + 90% distilled water). Feces and urine were collected

daily and stored in the refrigerator (4-8ºC) until the end of each period, when sub-samples were

mixed together.

Growth study

Live weight was recorded in the morning before feeding at the beginning and at 10-day

intervals until the end of the 90-day experiment. Live weight gain was calculated from the linear

regression of live weight (Y) on days from the start of the experiment (X). Feed consumption was

recorded daily. Refusals were collected from individual animals every morning before offering new

feed. Samples of Bauhinia acuminata, water spinach and cassava foliage (offered and residues)

were separated into stems and leaves (containing attached petioles). Representative samples of each

component were stored at -18°C until they were analysed. Samples of rumen fluid were taken on

the last day of the experiment, using a stomach tube.

22

Chemical analyses

The samples of feeds offered and refused were analysed for DM, NDF, ADF, N and ash

according to AOAC (1990) methods. The pH of rumen fluid was measured with a digital pH meter,

prior to addition of sulphuric acid for subsequent analysis of ammonia by steam distillation (AOAC,

1990) and VFA by high pressure liquid chromatography (Water model 484 UV detector; column

novapak C18; column size 3.9 mm x 300 mm; mobile phase 10 mM H2 PO4 [pH 2.5]) (Samuel et

al., 1997). Solubility of the protein in the diet components was determined by extraction with M

NaCl (Whitelaw et al., 1961).


Metabolism study

The data were analyzed by the general linear model (GLM) in the ANOVA program of the

Minitab software (Minitab, 2014).

The statistical model used in the digestibility study was:

Yijk = μ + Ti + Pj + Ak + eijk

In where, Yijk = Dependent variables., μ = Overall mean., Ti = Treatment effect (i=1-4)., Pj =

Column effect (j=1-4)., Ak = Row effect (k=1-4)., eijk = Random error

Growth study

The statistical model was:

Yijk = μ + Bk + Pi + Aj + P i*Aj+ eijk

Where: Yijk is dependent variables., μ is overall mean., Bk is the effect of live weight., Pi is

the effect of foliages source (water spinach and cassava foliage)., Aj is the effect of brewers’ grains

source., (P*A)ij is the interaction between source of foliages and source of brewers’ grains and eijk is

random error

RESULTS

Chemical composition of diet components

The low values for solubility of the protein in the leaves of Bauhinia acuminata and cassava,

and the high values for the leaves of water spinach (Table 2), are in agreement with previous

observations (Silivong and Preston, 2016) and are assumed to reflect different levels of tannin-rich

compounds in the leaves of all three species.

23

Table 2. Chemical composition of dietary ingredients (% in DM, except DM which is on fresh basis)

DM N*6.25 Ash Protein solubility, % NDF ADF

Bauhinia leaves 40.0 15.0 21.2 23.7 43.7 32.4

Bauhinia stem 38.1 12.3 4.29 - 42.7 31.5

Cassava leaves 32.1 22.2 4.48 31.4 48.7 34.4

Cassava petiole 16.8 16.7 6.39 - 48.3 38.6

Cassava root chips 82.4 2.81 2.23 - - -

Water spinach 8.16 18.3 9.74 69.4 42.3 33.3

Brewers’ grains 28.7 27.2 38.1 - 40.7 29.5

Biochar - - 38.3 - - -

Metabolism study

The two factors had contrasting effects on digestibility of DM and on daily N retention

(Table 3). Supplementation with brewers’ grains increased the digestibility of DM but the effect

was more pronounced when cassava foliage was the source of additional protein as compared with

water spinach. Daily N retention was similar for both foliages in the absence of brewers’ grains but,

when brewers’ grains were added, N retention was greater with cassava than with water spinach.

Table 3. Mean values of apparent digestibility and N balance in goats fed Bauhinia acuminata supplemented with

water spinach or cassava foliage, with (BG) and without (No-BG) brewers’ grains

Items

CF WS SEM p

No-BG BG No-BG BG SEM SEM

Foliage*BG P Foliage P BG

P

Foliage*BG


DM 68.4 74.9 69.9 72.3 0.60 0.86 0.558 <0.001 0.035

N balance, g/day

Intake 14.0 14.8 13.8 14.1 0.45 0.63 0.474 0.414 0.619

Feces 4.8 3.8 4.7 4.5 0.34 0.48 0.545 0.199 0.393

Urine 2.9 2.3 2.5 2.2 0.28 0.40 0.47 0.245 0.715

Retention 6.28 8.78 6.64 7.48 0.25 0.35 0.208 <0.001 0.037

N retention as:

% N intake 44.8 59.5 48.2 53.0 1.80 2.54 0.555 0.002 0.073

% N digested 68.6 79.2 73.0 78.1 2.12 2.99 0.585 0.022 0.368

BG: Brewer’s grain, CF: Cassava foliage, d: day, g: Gram, No-BG: Non-Brewer’s grain, P:

Probability value, SEM: Standard error of the mean with dferror: 0, WS: Water spinach

24

Growth study

The Bauhinia acuminata foliage accounted for two thirds of the total DM consumed (Table 4).

Other components were in similar proportions in each of the diets, except for the brewers’ grains

which was slightly higher (5% of diet DM) compared with the planned level of 4% of diet DM.

Addition of the brewers’ grains resulted in a small increase in diet crude protein content from 13.6 to

14.2% and from 13.8 to 14.5%, for the cassava foliage and water spinach treatments, respectively.

Table 4. Mean values of feed intake by goats fed Bauhinia acuminata plus cassava root chip supplemented with water

spinach or cassava foliage and/or brewer’s grain

Items

CF WS SEM p

No-BG BG No-BG BG SEM SEM Foliage*BG P Foliage P BG P Foliage*BG

DM intake, g/d

Bauhinia 395 403 380 384 1.94 2.74 <0.001 0.026 0.483

Water spinach - - 171 171 0.39 0.55 - 0.988 0.988

Cassava foliage 49 54 - - 0.43 0.60 - - -

Brewer’s grain - 0.8 - 1.5 0.12 0.16 0.045 - 0.045

Cassava root chip 1.6 2.5 2.2 2.3 0.10 0.14 0.130 <0.001 0.009

Biochar 7.9 8.1 8.0 8.1 0.02 0.03 0.130 <0.001 0.009

Total, g/day 583 628 591 627 2.55 3.61 0.375 <0.001 0.221

DM intake g/kg LW 34.4 35.2 34.0 35.6 0.10 0.15 0.911 <0.001 0.010

BG: Brewer’s grain, CF: Cassava foliage, d: day, g: Gram, Kg: Kilogram, LW: Live weight, No-

BG: Non-Brewer’s grain, P: Probability value, SEM: Standard error of the mean with dferror: 9, WS: Water

spinach

There was an interaction between the effects of the two dietary factors on DM intake,

growth rate and DM feed conversion (Table 5). When the protein-rich foliage was from cassava, the

supplement of brewers’ grains increased the DM intake and the growth rate and improved the feed

conversion but did not affect these criteria when the supplementary protein source was water

spinach. This result is in line with the findings of Sina et al., 2017 who supplemented brewers’

grains (5% of diet DM) to goats fed fresh cassava foliage or water spinach, as the sole diet. In that

study there was a 129% increase in live weight gain when brewers’ grains were added to cassava

foliage, compared with only 25% improvement on the water spinach diet.

25

Table 5. Mean values for live weight, live weight change, DM intake and DM feed conversion for goats fed Bauhinia

acuminata supplemented with cassava or water spinach foliage, with or without brewers’ grains (interaction effects)

Items

CF WS SEM p

No-

BG BG

No-

BG BG SEM

SEM

Foliage*BG

P

Foliage P BG

P

Foliage*BG

Live weight, kg

Initial 14.4 14.5 14.5 14.4 0.39 0.54 0.893 0.822 0.964

Final 20.7 20.9 20.1 21.4 0.59 0.83 0.826 0.134 0.378

Daily gain, g/day 58 83 68 75 2.61 3.69 0.858 0.001 0.032

DM intake, g/kg LW 34.4 35.2 34.0 35.6 0.10 0.15 0.911 <0.001 0.010

DM feed conversion 10.1 7.6 8.8 8.4 0.19 0.27 0.397 <0.001 0.002

BG: Brewer’s grain, CF: Cassava foliage, d: day, g: Gram, Kg: Kilogram, LW: Live weight, No-BG:

Non-Brewer’s grain, P: Probability value, SEM: Standard error of the mean with dferror: 9, WS: Water spinach

The higher values for rumen ammonia on the diets with water spinach (Table 6) were to be

expected in view of the greater solubility of the protein in water spinach compared with cassava

foliage (Table 2). However, on all diets, ammonia levels were sufficiently high to support normal

rumen function. On each foliage source, rumen ammonia values were higher when brewers’ grains

were included in the diet. There were minor differences in molar proportions of the VFA, and the

Ac:Pr ratio, apparently related to the treatments; however, the small order of magnitude of the

differences means they are unlikely to be of importance in relation to animal performance.

Table 6. Molar VFA proportions in rumen fluid from goats fed Bauhinia acuminata supplemented with water spinach

or cassava foliage, with and without brewers’ grains

Items

CF WS SEM p

No-BG BG No-BG BG SEM SEM

Foliage*BG

P

Foliage P BG

P

Foliage*BG

Molar %

Acetic 65.55 64.93 66.28 64.85 0.20 0.28 0.263 0.003 0.174

Propionic 24.83 23.50 24.08 24.60 0.21 0.29 0.56 0.196 0.008

Butyric 9.63 11.58 9.65 10.80 0.05 0.07 <0.001 <0.001 <0.001

Ac:Pr ratio 2.64 2.76 2.75 2.64 0.03 0.04 0.862 0.949 0.017

Rumen pH 7.06 7.05 6.99 6.90 0.02 0.03 0.01 0.166 0.233

NH3, mg/liter 186 194 215 232 1.31 1.85 <0.001 <0.001 0.003

BG: Brewer’s grain, CF: Cassava foliage, NH3: Ammonia, No-BG: Non-Brewer’s grain, P:

Probability value, pH: Percentage of Hydrogen Ion, SEM: Standard error of the mean with dferror: 9, VFA:

Volatile Fatty Acids, WS: Water spinach

26

DISCUSSION

We propose that the interaction in the degree of improved animal performance, according to

whether the brewers’ grains were added to the diet with cassava foliage, compared with the diet

containing water spinach, was because the brewers’ grains act as a prebiotic when included in diets

containing potentially toxic elements such as the cyanogenic glucosides present in cassava foliage.

A similar explanation can be applied to the effects of “Kilao” (the byproduct from the

fermentation/distillation of “rice wine”) in increasing growth and feed conversion of cattle fed

ensiled cassava root and cassava foliage (Sengsouly and Preston, 2016). The improved performance

appears to be manifested by increased diet digestibility and improved biological value of the

digested protein. The greater response to brewers’ grains when cassava foliage was fed, compared

with water spinach, could be because of enhanced capacity to detoxify the cyanogenic glucosides

present in cassava foliage as reported by Binh et al., 2017.

CONCLUSIONS

- Supplementing growing goats with brewers’ grains (5% of diet DM) increased diet

digestibility and the biological value of the absorbed protein, resulting in improvement of live

weight gain of 44% and in DM feed conversion of 25% when the basal diet was a legume tree

foliage (Bauhinia acuminata) and the protein supplement was cassava foliage. Comparable data

when water spinach was the protein supplement were relative improvements of 11 and 5%.

- It is proposed that brewers’ grains, a fermented byproduct from brewing “beer”, act as a

prebiotic when added to a diet containing potentially toxic elements such as the cyanogenic

glucosides present in cassava foliage.

27

CHARPTER 5: EFFECT OF SWEET OR BITTER CASSAVA LEAVES AND BIOCHAR

ON METHANE PRODUCTION IN AN IN VITRO INCUBATION WITH SUBSTRATES OF

BAUHINIA ACUMINATA AND WATER SPINACH (Ipomoea aquatica)

INTRODUCTION

Reducing GHG emissions from agriculture, especially from livestock, is a priority in order

to reduce global warming (Sejian et al., 2010). Ruminants - cattle, buffalo, sheep and goats - are the

major contributors of methane emissions from the agriculture sector (Lassey, 2007). There is

therefore a need to develop feeding systems for ruminants that will result in reduced emissions of

methane gas from the enteric fermentation in these animals. Promising ways to do this are: (i) by

the feeding of biochar (Leng et al., 2012) derived from the carbonization of fibrous wastes (Orosco

et al., 2018); and (ii) using as protein supplement the foliage from bitter as opposed to sweet

cassava (Phuong et al., 2012). Cassava products contain cyanogenic glucosides which liberate

hydrocyanic acid (HCN) when emzymically degraded. Cyanogenic glucosides exist as linamarin

and lotaustralin in unbruised leaf (Makkar et al., 1995; Grainger et al., 2009). When the cellular

structure is broken, the glucoside is exposed to extracellular enzymes such as linamarase which

gives rise to toxic hydrocyanic acid. In studies on biodigestion of cassava residues it was shown that

the HCN liberated in the digestion process was toxic to methanogenic bacteria (Smith et al., 1985;

Rojas et al., 1999). It is therefore postulated that a similar process could take place in the rumen of

cattle fed cassava products, which could be an advantage as a strategy for reducing greenhouse gas

emissions from ruminant animals. Cassava varieties are generally categorized into “sweet” varieties

suitable for human consumption, and “bitter” varieties more appropriately used for industrial

production of starch. It is understood that the ‘bitter” varieties are so-called because they have

higher concentrations of cyanogenic glucosides making them potentially toxic to humans and

animals. The objective of the research described in this paper was to combine both of these factors

as a means to reduce methane production in goats fed foliage from the legume tree Bauhinia

acuminata supplemented with foliage from water spinach.



The experimental design was a 2*2 factorial arrangement of 4 treatments with four

replications. The factors were: - Source of cassava leaves: Sweet (SC) or bitter (BC) variety

- Biochar: With (Bio) or without (NoBio) biochar

Table 1. Composition of substrate (% DM basis)

SC-Bio SC-NoBio BC-Bio BC-NoBio

Sweet cassava leaves 24 25

Bitter cassava leaves 24 25

Biochar 1 1

Bauhinia leaves 60 60 60 60

Water spinach leaves 10 10 10 10

Cassava root chips 5 5 5 5

28

Preparation of substrate and the in vitro system, data collection, measurements and

chemical analyses were refered of the experiment 1 in the chapter 2.


The data were analyzed by the general linear model option of the ANOVA program in the

Minitab software (Minitab, 2014). In the model the sources of variation were: treatments, replicates

and error.

The statistical model was:

Yijk = μ + Pi + Aj + Pi*Aj+ eijk

Where: Yijk is dependent variables., μ is overall mean., Pi is the effect of cassava leaves.,

Aj is the effect of biochar source., (P*A)ij is the interaction between source of cassava leaves

and source of biochar and eijk is random error

RESULTS


Protein solubility was lowest in Bauhinia acuminata, was lower in bitter than in sweet

cassava leaves and highest in water spinach leaves (Table 3).

Table 3. The chemical composition of substrate ingredients (% in DM, except DM which is on fresh basis)


Bauhinia leaves 35.6 14.7 6.6 23.4 1.1 43.7 32.4

Bauhinia stem 38.1 12.3 4.29 - 42.7 31.5

Sweet cassava leaves 32.1 22.2 4.48 31.4 48.7 34.4

Sweet cassava petiole 16.8 16.7 6.39 - 48.3 38.6

Bitter cassava leaves 32.44 20.1 5.5 31.0

Cassava root chip 35.4 3.2 3.4

Water spinach 10.6 18.5 9.7 66.4

Biochar - - 38.3

The linear increase in methane concentration in the gas with duration of the incubation (Table

4) is similar to the trends observed by Outhen et al., 2011; Binh Phuong et al., 2011; Inthapanya et al.,

2011 and Silivong and Preston, 2015 who used the same in vitro fermentation model. These results

indicate that there is a lag time either in the growth of organisms that ferment carbohydrate to VFA

and hydrogen, and/or in the growth of those that convert hydrogen to methane.

29

Table 4. Mean values for gas production, percentage of methane in the gas, DM digested and methane

production per unit DM digested, according to source of cassava leaves (sweet SC or bitter BC) and with

(Bio) or without ( NoBio) biochar

CL

p

Bio

p SEM

Interaction

SC BC Bio NoBio SEM p

0-6 h

Gas, ml 640 581 0.001 614 608 0.654 9.62 13.59 0.787

CH4, % 9.5 8.4 0.007 8.9 9.0 0.724 0.24 0.35 0.724

DM digested, % 54.9 46.4 <0.001 52 49.3 0.021 0.72 1.01 0.687

CH4, ml/g DMD 9.2 8.8 0.407 8.8 9.3 0.349 0.36 0.51 0.584

0-12 h

Gas, ml 871 815 0.001 849 838 0.382 8.76 12.40 0.921

CH4, % 17.5 16.2 <0.001 16.6 17.1 0.015 0.13 0.19 0.192

DM digested, % 61.1 50.8 <0.001 57.9 54.0 <0.001 0.46 0.65 0.061

CH4, ml/g DMD 20.9 21.7 0.156 20.4 22.2 0.006 0.39 0.55 0.265

0-18 h

Gas, ml 991 829 <0.001 945 875 0.005 14.5 20.49 0.905

CH4, % 22.9 20.7 <0.001 21.1 22.5 0.003 0.27 0.39 0.435

DM digested, % 66.2 55.0 <0.001 62.4 58.8 <0.001 0.45 0.64 0.102

CH4, ml/g DMD 28.5 26.2 <0.001 26.6 28.1 0.006 0.33 0.46 0.192

0-24 h

Gas, ml 1,438 1,314 0.002 1,410 1,341 0.056 22.9 32.44 0.792

CH4, % 28.5 25.8 <0.001 26.9 27.5 0.028 0.18 0.26 0.180

DM digested, % 72.6 59.4 <0.001 68.4 63.6 <0.001 0.53 0.75 0.499

CH4, ml/g DMD 47.1 49.3 0.048 46.7 49.7 0.012 0.70 0.99 0.920

BC: Bitter cassava leaves, Bio: Biochar, CL: Cassava leaves, P: Probability value, SEM: Standard

error of the mean with dferror: 9, SC: Sweet cassava leaves.

30

The methane content of the gas was reduced when leaves of bitter cassava replaced leaves of

sweet cassava as protein source and when 1% of biochar was added to the substrate. The magnitude

of the differences was relatively small but consistent for all incubation times. The proportion of the

substrate DM that was digested during the incubation was increased when biochar was included in

the substrate and reduced when the protein supplement was from bitter compared with sweet

cassava. Addition of biochar reduced the production of methane per unit substrate digested.

However, there was no consistent trend for effects of bitter versus sweet cassava. As was to be

expected the production of methane per unit substrate digested increased linearly with duration of

the incubation.

DISCUSSION

The reduction in production of methane when leaves of bitter cassava replaced those from

sweet cassava has been reported in several in vitro incubations (Phuong et al., 2012; Binh et al.,

2018) and appears to be a direct effect of the higher HCN levels in the bitter varieties being toxic to

methanogens (Smith et al., 1985). However, the major reduction (18%) in digestibility in the 24h

incubation, when leaves from bitter cassava replaced those from sweet cassava, has not previously

been reported; in fact, the opposite effect was observed by Phuong et al., 2012. The logical

assumption is that the reduced digestibility reflected a more general HCN toxicity on the activity of

all rumen microbes. The reduction in methane production due to biochar was much less than has

been observed in previous studies. A reduction of 13% was recorded by (Phuong et al., 2012; of 8%

by Vongkhamchanh et al., 2015; and 12% by Binh et al., 2018). The implication is that the sample

of biochar used in this experiment may have been of inferior quality in terms of its relative surface

area: weight ratio (and hence its capacity to support microbial communities in biofilms [Leng,

2017]). This stresses the need for a simpler quality test than the standard “BETS” ratio (for which

the measuring equipment is not available in laboratories in Lao PDR).

CONCLUSIONS

(i) Increasing the length of the incubation from 6 to 24h in an in vitro rumen fermentation

increased methane concentration in the gas and methane produced per unit substrate DM digested.,

(ii) The methane content of the gas was reduced when leaves of bitter cassava replaced leaves of

sweet cassava as protein source and when 1% of biochar was added to the substrate. The magnitude

of the reduction due to biochar was relatively small but consistent for all incubation times., (iii) The

proportion of the substrate DM that was digested during the incubation was increased when biochar

was included in the substrate and reduced when the protein supplement was leaf meal from a bitter

compared with a sweet cassava variety.

GENERAL CONCLUSIONS

(i) It was confirmed that goats fed a tannin-rich tree foliage, such as Bauhinia acuminata,

responded with improved diet digestibility, N retention and growth rate when the Bauhina

acuminata was supplemented with a highly fermentable vegetable plant such as water spinach

(Ipomoea aquatica)., (ii) An important negative effect was that the improvement in diet digestibility

by supplementation with water spinach led to increases in methane production per unit diet DM

digested. The increase in methane production was postulated as being due to the much higher

solubility of the protein in water spinach compared with the Bauhinia acuminata., (iii) The methane

31

concentration of the gas in in vitro rumen incubations increases linearly with the length of the

fermentation., (iv) Supplementing Bauhinia acuminata foliage with leaves from a bitter variety of

cassava reduced the in vitro production of methane when compared with supplementation by leaves

from a sweet variety of cassava., (v) It is postulated that the cyanogenic glucosides present in

greater concentration in the leaves of bitter than in sweet cassava could be the reason for the

reduction in methane production., (vi) Ensiled brewers’ grains fed as an additive (5% as DM) to a

diet of Bauhinia acuminata improved the digestibility, N retention and growth rate of goats. The

degree of improvement was greater when the Bauhinia acuminata was supplemented with cassava

foliage instead of water spinach., (vii) Biochar fed at 1% of a diet of Bahinia acuminata and

cassava foliage was as effective as brewers’ grains in improving the growth rate of the goats.

IMPLICATIONS

(i) Bauhinia acuminata foliage can support growth rates of >60 g/day in local goats when it

is supplemented with foliage from a sweet variety of cassava foliage., (ii) Water spinach also

improves growth rates of goats fed Bauhinia acuminata foliage but is not recommended as this

practice will result in increased production of rumen methane., (iii) Ensiled brewers’ grains and

biochar fed to goats as additives (5% for brewers’ grains; 1% for biochar) probably act as

“prebiotics” to improve growth performance and assist in detoxification in the animal of the

products from enzymic breakdown of secondary plant compounds such as cyanogenic glucosides.

FURTHER RESEARCH

Cassava foliage is an important supplement to improve productivity of goats browsing on

native trees and shrubs with the probability that this practice will also reduce enteric methane, an

important greenhouse gas. Cassava foliage is available in large quantiles in Lao PDR when the roots

are harvested for industrial starch production; It can also be produced by repeated harvest at 3-4

month intervals when the crop is grown for forage production. Varieties grown for starch

production have been selected for high yield but this is also associated with higher levels of

potentially toxic cyanogenic glucosides that give rise to toxic HCN when consumed by animals.

Biochar is the carbon-rich byproduct of the carbonization of fibrous biomass by pyrolysis at high

temperatures (700-900°C). It is an important component of strategies to reduce global warming as

when applied to the soil the carbon in the biochar is not oxidized. This process is thus a natural way

to sequester carbon from the atmosphere, an essential feature of activities required in order to

reduce the risks of climate change. To respond to the opportunities and multiple benefits from: (i)

feeding of cassava foliage as a protein supplement for goats browsing on trees and shrubs; and (ii)

the associated use of biochar as a dietary additive, it is proposed that research should be prioritized

to: (i) Definition of the relative roles of sweet and bitter varieties as supplements in the feeding

system of goats and other ruminant animals., (ii) The production of biochar at farm level from

fibrous crop byproducts (eg: cassava stems) and its role as a “prebiotic” feed additive in conserving

animal health and improving productivity, especially in diets based on cassava foliage.

32

PUBLICATION LIST

I. Silivong, P., Preston, T.R., Van, N.H. and Hai, D.T., 2018. Brewers’ grains (5% of diet

DM) increases the digestibility, nitrogen retention and growth performance of goats fed a

basal diet of Bauhinia accuminata and foliage from cassava (Manihot esculenta Crantz) or water

spinach (Ipomoea aquatica). Livestock Research for Rural Development. Volume 30, Article #55.

Retrieved May 3, 2018, from http://www.lrrd.org/lrrd30/3/siliv30055.html

II. Silivong, P., Preston, T.R., Van, N.H. and Hai, D.T., 2018. Effect of sweet or bitter

cassava leaves and biochar on methane production in an in vitro incubation with substrates

of Bauhinia acuminata and water spinach (Ipomoea aquatica). Livestock Research for Rural

Development. Volume 30, Article #163.

http://www.lrrd.org/lrrd30/9/psivil30163.html

http://www.lrrd.org/lrrd30/3/siliv30055.html

http://www.lrrd.org/lrrd30/9/psivil30163.html

Documents

IMPROVED UTILISATION OF BAUHINIA ACUMINATAsdh.hueuni.edu.vn/attachments/article/1363/... · tannins (Silivong and Preston, 2015). Water spinach (Ipomoea aquatica) is cultivated for