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ENSILING CHARACTERISTICS, DIGESTIBILITY AND PALATABILITY OF TROPICAL GRASSES AS AFFECTED BY GROWTH
STAGE, CHOPPING LENGTH AND ADDITIVES
by
Sujatha Panditharatne
Dissertation submitted to the Graduate Faculty of the Virginia Polytechnic Institute and State University
in partial fulfillment of the requirements for the degree of
Doctor of Philosophy
in
Animal Science (Forage Management and Utilization)
APPROVED:
J. H. Fontenot, Co-chairman V. G. Allen, Co-chairman
R. E. Blaser
M. c. N. ~ayasuriya
K. E. Webb, Jr.
L.A. Swiger, Department Head
December, 1984
Blacksburg, Virginia
ACIC)JOWLEDGEMENTS
The author wishes to express her sincere thanks to all
individuals for their assistance and encouragement
throughout this study and her entire graduate program.
To the members of her graduate committee, Dr. J. P.
Fontenot, Dr. V. G. Allen, Dr. R.E. Blaser, Dr. K. E. Webb,
Jr., Dr. M. C. N. Jayasuriya and Dr. L. A. Swiger, the
author expresses her appreciation for their assistance.
The . .... ass1.s1..ance, guidance, patience and understanding
Dr. J. P. Fontenot has extended throughout this study is
especially appreciated. The encouragement~ guidance and
patience of Dr. V. G. Allen in conducting this study is also
appreciated. Special thanks are extended to Dr. M. C. N.
Jayasuriya, to whom the author is indebted for his technical
assistance, patience and counselling.
The author wishes to extend her special thanks to Mr.
Hugh Chester-Jones for many hours of assistance. Special
thanks are expres3ed to Professor A. S. B. Rajaguru and his
staff at Mawela Farm, Univer3ity of Peradeniya, Peradeniya,
Sri Lanka for many hours of 21.ssi sta:i.ce. Thar.ks are al so
extended to Miss Sandya Illep2ruma for her technical
assistance throughout the study.
Appreciation is expressed to the consortium for
International Agricultural Eo.ucation Development for the
scholarship awarded to the autl1cr, which made this study
ii
possible.
The author wishes to extend her sincere thanks to Miss
Laura Coater and Mrs. E. Stephens for their patience and
effort in typing this manuscript.
Finally, the author wishes to
appreciation to her parents and family,
moral support throughout this project.
convey her
for their
warmest
love and
The author lovingly
dedicates this dissertation to her parents.
iii
TABLE OF CONTENTS
ACKNOWLEDGEMENTS •
LIST OF TABLES ••
LIST OF FIGURES ••
CHAPTER I. INTRODUCTION ••
CHAPTER II. REVIEW OF LITERATURE.
Guinea Grass. • • • • . • . . Effect of Cutting Frequency on Yield Effect of Cutting Frequency on Composition Digesti~ility of Guinea Grass.
Napier Breed 21 (NB-21) • Dry Matter Yield •. Chemical Composition •• Digestibility.
Silage Additives •. Cassava Tuber Meal Coconut Oil Meal •
Fermentation Process Involved in Ensiling Tropical Forages. . . . • . . ...
CHAPTER III. JOURNAL ARTICLE I. El~SILING CHARACTERISTICS OF TWO TROPICAL FORAGES •
Summary • . . , Introduction •. Methods and Materials Results •...• Discussion •... Literature Cited.
CHAPTER I". JOURNAL ARTICLE II. EFFECT OF STAGE OF GROWTH AND CHOPPING LENGTH ON DIGESTIBILITY AND PALATABILITY OF GUINEA-'A' GRASS.
Summary •. Introduction. Methods and Materials Results and Discussion. Literature Cited •...
iv
page
ii
vi
viii
1
6
6 6 9
11
13 13 15 17
18 20 21
23
33
33 34 35 41 59 64
68
68 69 70 73 81
page
CHAPTER V. EFFECT OF CUTTING FREQUENCY ON YIELD OF GUINEA-'A' AND NB-21 FODDERS IN SRI LANKA 85
Summary. . . . 85 Introduction. . 85 Methods and Materials 86 Results and Discussion. . 88 Literature Cited. 94
GENERAL DISCUSSION 95
LITERATURE CITED 101
APPENDIX 112
VITA. . 117
ABSTRACT
V
table
1
2
3
4
5
6
7
8
9
10
11
12
13
14
LIST OF TABLES
Composition of Cassava Tuber Meal
Composition of Coconut Oil Meal.
Composition of Cassava Tuber Meal and Coconut Oil Meal Used in Small Silo Study. . . . . . ...
Composition and Fermentation Characteristics of Initial Samples of Guinea-'A' and NB-21 as Affected by Stage of Growth, Small Silo Study ..•...•....
Composition of Pre-ensiled Mixtures of Guinea-'A' and NB-21 as Affected by Additives, Small Silo Study.
Fermentation Characteristics of Pre- and Post-ensiled Mixtures of Guinea-'A' and NB-21 as Affected by Stage of Growth, Small Silo Study ............ .
Fermentation Characteristics of Pre- and Post-ensiled Mixtures of Guinea-'A' and NB-21 as Affected by Additives, Small Silo Study ...........•
Effect of Period of Growth of Guinea-'A' and NB-21 Upon Dry Matter Content and Volatile Fatty Acid Concentration, Small Silo Study .....
Effect of Ensiling Various Additives Upon Dry Matter Content and Volatile Fatty Acid Concentration, Small Silo Study ................. .
Composition of Initial Samples of Guinea-'A' Grass Used in Chopping Length Study, SIT411 Silo Study ..
Fermentation Characteriitics of Pre- and Post-ensiled Mixtures as Affected by Chopping Length, Small Silo Study . . . . . . . . . . . . . . . . . . . . · • · ·
Effect of Chopping Length Upon Dry Matter Percentage and Volatile Fatty Acid Concentration, Small Silo Study
Effect of Growth Period on the Composition of Initial Samples of Guinea-'A' Grass, Large Silo Study ....
Fermentation Characteristics of Pre- and Post-ensiled Guinea-'A' Grass as Affected by Growth Period, Large Silo Study .............. , ...... .
vi
page
22
24
37
42
43
45
46
49
50
51
52
54
55
56
table
15
16
17
18
19
20
21
22
23
24
25
26
27
28
Fermentation Characteristics of Pre- and Post-ensiled Guinea-'A' as Affected by Chopping, Large Silo Study.
Effect of Growth Stage Upon Dry Matter Percentage and Volatile Fatty Acid Concentration, Large Silo Study.
Effect of Chopping Upon Dry Matter Percentages and Volatile Fatty Acid Concentration, Large Silo Study
Composition and Cell Wall Fractions of Silage in Sheep Metabolism and Palatability Trials ..••••••.••
Apparent Digestibility of Guinea-'A' Silage by Sheep.
Dry Matter Intake of Sheep Fed Guinea-'A' Silage ...•
Dry Matter Yield of Guinea-'A' and NB-21 as Affected by Length of Growth Period .••.•.•••..•.•
Dry Matter Yield of Guinea-'A' and NB-21 as Affected by Growth Period. • . . . • • . . • . • . •...
Leaf to Stem Ratio and Plant Heights of Guinea-'A' as Affected by Growth Period ....•••
Leaf to Stem Ratio and Plant Heights of NB-21 as Affected by Growth Period •.•.••.
Composition of the Mineral Mixture Used in Animal Trials. • . • • • • • . • • • • • ,
Example of Analysis of Variance, Small Silo Study
Example of Analysis of Variance, Palatability Trial.
Fermentation Characteristics of Post Ensiled Mixtures (Large Silo) ....•••....•.•.••....
vii
page
58
60
61
74
75
78
89
90
92
93
113
114
115
116
figure
1
2
3
Map of the World.
Map of Sri Lanka
LIST OF FIGCRES
Classification of Silage Additives.
viii
page
2
3
19
CHAPTER I
INTRODUCTION
The major problem which hinders expansion of the
ruminant industry in tropical countries ( figure 1) '
including Sri Lanka (figure 2), is the lack of good quality
forage throughout the year. Seasonal rainfall in most parts
of Sri Lanka results in a fluctuating supply of pasture,
thus highlighting the urgent need for forage conservation
for periods of short feed supply. Forage could be conserved
eithe~ as hay or silage depending on weather conditions. In
tropical countries, there are various advantages of silage
over hay. Hay drying is a problem in Sri Lanka, because the
periods of maximum forage production coincide with frequent
rains. Rain on cut herbage causes losses of soluble
carbohydrates,
digestible dry
protein
matter
and
by
minerals; and losses of
respiration; and microbial
decomposition. Prolonged wet weather causes molding and
results in material that is not edible.
High relative humidity, one of the characteristics of
the humid tropics, makes .... 11.. difficult to dry hay. High
humidity will permit the drying of grass only to a certain
moisture content which may be too high for safe storage of
grass as hay. Therefore, it appears to be more feasible to
make silage than hay.
1
FIG. I. MAP OF THE WORLD SHOWING, BETWEEN THE HEAVY BLACK LINES, THE REGIONS CONSIDERED TO BE IN THE TROPICS.
N
ORY ZONE (ONE RAINFALL SEASON)
WET ZONE (TWO RAINFALL SEASONS)
COCONUT PLANTATIONS ---..J.=
COLOMBO
BOUNDARY ENCLOSING TEMPERATE ZONE (AVERAGE ANNUAL TEMPERATURE< 21C)
WET
FIG. 2. MAP OF SRI LANKA.
3
ZONE
0 16 32 48 64 80 Km
4
Guinea grass, ( Panicum maximum-Jacq) ecotype 'A' in
low- and mid-country of Sri Lanka, is extremely resistant to
drought and grows . . , rapia ... y. Instead of using improved
varieties, dairy farmers utilize Guinea-'A' as the main
source of forage for their cattle. The recent trend has
been to use Guinea-' A' as a source of fodder rather than
attempting to eradicate and replace it with improved
varieties.
Napier breed 21 (NB-21), a hybrid derived from a cross
between ordinary Napier (Pennisetum purpureum, Schumac.) and
pearl millet (Pennisetum americanum, L.), has potential
value for feeding ruminants in Sri Lanka. This hybrid is
resistant to Helminthosporium fungus disease, and gives high
dry matter yields of high quality forage.
Tropical forages are low in water-soluble carbohydrates
(Catchpoole and Henzel, 1971; Wilson and Ford, 1973; Tosi,
1973; Noble and Lowe, 1973), which are important for
ensiling (Wilson a~d Ford, 1973; Wilkinson and Phipps,
1979). Research in temperate regions has shown that
increasing water soluble-carbohydrates by adding cereals or
molasses when ensi ling have resulted in increased lactic
acid fermentation (McDonald, 1981). Manioc (Manihot
esculenta, Crantz) tuber meal and coconut {Cocos nucifera,
L.) oil meal could improve fermentation since they are
readily available in Sri Lank&.
5
The present studies were conducted to investigate ( 1)
the ensiling characteristics of Guinea-'A' and NB-21 cut at
different defoliation intervals with and without additives
and (2) the effect of freque::1.cy of defoliation, with and
without chopping on digestibility and palatability of
Guinea-'A' grass.
Guinea Grass
CHAPTER II
REVIEW OF LITERATURE
Guinea grass is one of the most widely used tropical
perennial forages. According to Motta (1953) the leaves are
bright green and it grows to a height varying from 90 to 300
cm. The leaves are up to 60 cm long, 4 to 20 mm wide, with
and without pubescence, and it has a somewhat stout stem.
Its inflorescence is a panicle and establishment of grass
can be either vegetative ( from rooted sets) or from seed.
He stated that this grass is indigenous to Africa, however,
it is now grown in most parts of the world. The range of
distribution is from sea-level to altitudes of around 1982 m
(Motta, 1953); it can be grown on poor soils in regions of
low rainfall under a low standard of grassland management.
Establishment of Guinea grass is easy and it tolerates
wide ranges in soil moisture, soil fertility and pH (Oakes,
1966). Furthermore, this grass competes against weeds and
can produce high yields of forage of substantial nutritive
value. Several strains and ecotypes have been identified
due to the wide range of distribution throughout the world.
Guinea-'A' is one of the ecotypes growing in low- and mid-
country of Sri Lanka.
Effect of Cutting Frequency on Herbage Dry Matter Yield
of Guinea Grass. Guinea grass is high yielding among
6
7
tropical grasses, but varying·yields have been reported from
different countries due to variability in strains and
ecotypes, and varying systems of management under different
environmental conditions. Comparisons of such figures would
be of little value since management and climatic factors are
not given. However, these yields could give some indication
of the potentials of the grass. Numerous investigations
have shown that yields increase with length of harvest
interval (Watkins and Lewy, 1951; Vicente-Chandler et al. ,
1959; Oyenuga, 1960; Goonewardene et al., 1971).
With application of 363 kg/ha of nitrogen (N) in Puerto
Rico, Guinea grass produced 12,524, 14,879 and 19,822
k "h 1. 1 g a- yr- , dry basis, when cut at 40-, 60- and 90-d
intervals, respectively (Vicente-Chandler et al., 1959)
Oyenuga (1960) reported that the dry matter yields of
Guinea grass cut at 3, 6, 8 and 12 wk intervals were 11,974
16,065, 15,211 and 23,369 kg"ha-l.yr- 1 , respectively. He
suggested that these yields were high for Guinea grass since
no fertilizer was applied.
Oakes ( 1966), in dry tropics, found that the harvest
interval affected yield significantly during 3 of the 5 yr.
With N fertilization the mean dry matter yields were 39,576,
44,059, 47,767 and 51,476 kg"ha 1 ·yr- 1 for harvest intervals
of 2, 3, 4 and 6 mo, respectively.
Goonewardene and Appadurai (1971), studied frequency of
8
defoliation on the rate of regrowth and the output of
herbage dry matter per unit of land for Guinea 'B', which is
a popular ecotype in Sri Lanka. They have shown that
lengthened harvest interval increased yield of forage dry
matter. Pandi tharatne et al. ( 1978) showed the same trend
of increased dry matter yields with decreased frequency of
defoliation in Guinea grass-ecotype 'A'. The mean yields of
herbage dry matter were 8,745, 24,000 and 40,594
kg"ha- 1 ·yr- 1 for defoliation frequency of 15-, 30- and 45-d,
respectively.
Thomas ( 1976), working in the Malawi, reported dry
matter yield for nine cultivars of Guinea grass ranged from
8,067 to 17,238 kg/ha in the first season after
establishment, when the plots were. sampled at 28 d
intervals, cut to a height of 10 cm. Furthermore, Guinea
grass cv. 'Ntchisi', a local collection, produced the
largest mean dry matter of 9,303 kg/ha, whereas, cv.
'Coloratum' produced the lowest mean dry matter of 4,993
kg/ha for the three seasons. According to the above
results, a wide variation in yields for cultivars subjected
to similar management practices could be expected.
Omaliko (1980) reported that the mean dry matter yield
of Guinea grass was highest when the sward was cut every 10
wk and least when cut every 3 wk. According to his results,
increasing the intervals from 3 to 4 or from 4 to 5 wk but
9
not from 5 to 6 or from 6 to 8 wk, significantly increased
the total dry matter yield.
Effect of
Composition of
normal trend in
Frequency of Defoliation on Chemical
Guinea Grass. Guinea grass follows the
grasses, with a decrease of percent crude
protein with increased stage of growth, and a corresponding
increase in soluble carbohydrate and crude fiber. Several
workers have shown that the crude protein percentages of the
dry matter varies from around 11.5 at the young leafy stage
to about 4.0 at a mature stemmy stage (Vicente-Chandler et
ai., 1959; Oyenuga, 1960; Oakes, 1966; Goonewardene and
Appadurai, 1971; Thomas, 1976; Panditharatne et al., 1978).
Vicente-Chandler et al. (1959) of Puerto Rico, reported
that the protein content of Guinea grass decreased with
increasing length of harvest interval, averaging 7. 8, 6. 2
and 4.9%, dry basis, respectively, when cut at 40, 60 and 90
d. Furthermore, the dry matter content of the grass
increased with the length of harvest interval, averaging
20.2, 23.8 and 30.4%, when cut at 40, 60 and 90 d,
respectively.
with increased
Lignin content of Guinea grass also increased
length of harvesting intervals. Devendra
( 1977) in Malaysia reported 16. 7% crude protein and 28. 2%
fiber for var. Coloniao when cut at 21 d of age.
Oyenuga (1960), found that percentage crude protein was
inversely related to the length of cutting intervals, while
10
the percentage of dry matter and soluble carbohydrate were
directly related to the stage of maturity of Guinea grass.
The crude fiber values were high, a characteristic of
tropical fodder grasses, and were not consistent. The mean
crude protein of Guinea grass was about 12% when cut every 3
wk, declining from this value by about 45% to 6.4% when cut
every 12 wk.
Oakes (1966) recorded that the protein content of
Guinea grass dee lined with harvest interval. The percent
protein was 6.5, 5.2, 4.6 and 4.2 for defoliations of 2-,
3-, 4- and 6-mo, respectively. Goonawardene and Appadurai
( 1971), showed that Guinea grass cv. 'B' had the highest
crude protein at a 20 d growth cycle. The crude protein
content increased with frequency of defoliation from 10 to
20 d, and showed a rapid decline thereafter.
Thomas (1976) reported average crude protein
percentages of dry matter for six cultivars of Guinea- grass
ranged from 12.4 to 13.2, when harvested at 28 d intervals.
He stated that the crude protein content did not vary
appreciably among seasons or among cultivars.
Panditharatne et al. (1978), working with Guinea grass
cv. 'A', showed that the mean crude protein in herbage dry
matter increased significantly with age up to 30-d, and
declined rapidly thereafter. The crude protein was 10. 7,
13.2 and 9.9%, dry basis, when cut at 15-, 30- and 45-d,
11
respectively. On the other hand, Thomas et al. (1980)
showed that the mean crude protein of Guinea grass was
decreased from 7.5 to 7.2%, dry basis, when the frequency of
defoliation was increased from 30 to 45-d, whereas crude
fiber increased from 29.1 to 31.6%, respectively.
Digestibility of Guinea Grass. Digestibility affects
not only the efficiency of utilization of forages but also
the voluntary intake. Thus, it is very important for
efficient livestock production. Wilson and Ford (1971)
reported that tropical grasses were lower in alcohol- and
water-soluble sugars and in vitro dry matter digestibility
and higher in starch and structural (cell wall)
carbohydrates than Lolium perenne cultivars. The in vitro
dry matter digestibility of Guinea grass var. trichoglume
plant tops was about 71% at day/night temperature regime of
32.2/26.7 C, and the content of total non-structural
carbohydrates (alcohol-soluble and 60 C water-soluble plus
starch) was 27.5% on dry weight basis. Starch contents of
16 to 19% of dry weight were recorded by Wilson and Ford
(1971) for Guinea grass at 32.2/26.7 C.
In another study, Wilson and Ford (1973) showed that
temperate grasses accumulated much higher concentrations of
soluble carbohydrates than the tropical grasses. The
alcohol-soluble sugars were mainly glucose and fructose in
both temperate and tropical species, whereas the 100 C water
12
extracts were fructose for temperate species, and glucose
and galactose for tropical grass. They obtained 7.5 to 15%
of total alcohol-soluble carbohydrates in Guinea species.
The in vitro dry matter digestibility of Guinea grass var.
trichoglume harvested 18 d after the fifth leaf stage was
about 73.5% at day/night temperature regime of 32/24 C. All
of · these experiments were
environmental conditions and
Wilson (1973) reported that
digestibility of Guinea grass
59. 8%, and cell wall content,
71. 2% when harvested at 58-d
confined to controlled
very young plant material.
the in vitro dry matter
var. trichoglume tops was
on a dry matter basis, was
of age under a controlled
environment. Wilson and Ford (1971) and Wilson (1973)
concluded that the carbohydrate composition is one of the
factors which influences digestibility. Noble and Lowe
( 1974) reported a value of . 2 to 3. 5% of total alcohol-
soluble carbohydrates for Guinea grass var. Gatton in
Southeast Queensland.
Thomas ( 1976), working with six cul ti vars of Guinea
grass, reported that the digestible organic matter of
forages ranged from 60. 5 to 64. 2% when harvested at 28-d
intervals. According to Devendra (1977), the organic matter
digestibility for Guinea grass var. Serdang and Colonio,
recorded at 16 to 19, 21 to 28, 28 to 35, 35 to 42 and 42 to
49 d-of-age was 68.1, 69.3; 67.4, 67.5; 63.5, 57.3; 63.2,
13
60.8; 61.0 and 63.2%, respectively, for the two varieties.
Tosi (1973) showed that the water-soluble carbohydrate (WSC)
content of Guinea grass was about 1.74%, on wet basis
(6.26%, dry basis).
Napier Breed 21 (NB-21)
NB-21 is a tall perennial, resembling sugar-cane in
growth habit; it has deep roots to tap water from the lower
soil horizons. It is adapted to reasonably well-drained
soils but grows profusely on fertilized sandy soils. This
fodder can be propagated from stem cuttings consisting of
three to four nodes, or by division of rootstocks.
According to Dhanapala et al. ( 1972) NB-21 has juicy, non-
hairy foliage of high digestibility that grows rapidly.
This hybrid is resistent to Helminthesporium fungus disease,
and gives high dry matter yields of high quality forage.
Herbage Dry Matter Yield of Napier Hybrids. There are
many hybrids between Napier grass and other grasses which
differ in disease resistance, yield, leafiness and other
characteristics. Information on NB-21 is lacking. The
values for other Napier hybrids will also be included in
this review since it could give some indication of the
potential of the fodder.
It is generally accepted that lengthened harvest
interval increases yields of forage dry matter (Goonewardene
and Appadurai, 1971; Mani and Kothandaraman, 1980; Sanghi
14
and Raj, 1983). Goonawardene and Appadurai ( 1971) repo_rted
that the yield of Pusa Giant Napier hybrid (Pennisetum
purpureum. Schumac x Pennisetum typhoidem, Riche) decreased
with frequent cutting. According to Dhanapala et al. (1973)
NB-21 yields about 306 tons"ha- 1 ·yr- 1 , fresh matter basis,
compared with 173 tons"ha-1.yr- 1 for cultivar Pusa Giant
Napier.
In India, five Napier hybrids (Pennisetum purpureum x
Pennisetum americanum) gave yields of 67.4 to 90.4 t fresh
matter and 11.45 to 16.87 t dry matter/ha in 5 cuts; hybrid
NB-21 gave the highest dry matter yield (Raju et al., 1975).
There was no significant difference in contents of crude
fiber, ether extract, calcium, phosphorous, oxalic acid,
cellulose and digestible cellulose between the hybrids.
Gupta (1974) reported that NB-21 gave average yields of 29.6
t dry matter/ha containing 12. 6% crude protein and 2. 06%
oxalic acid compared with 21. 1 t, 9 . 3 % and 3 . 0%,
respectively, in the standard hybrid Pusa Giant Napier.
Tiwana and Bains (1977) reported that NB-21 gave a yield of
147 t fresh matter per hectare with 10.9% crude protein.
Mani and Kothandaraman (1980) studied the influence of
N and stage of cutting on the yield of hybrid Napier
varieties. According to their results, cutting the fodder
at an interval of 45 d, gave the highest green matter and
dry matter yield, when compared with 35- and 40-d. The dry
15
matter content increased with maturity and the variety NB-21
recorded the lowest green matter and dry matter yield when
compared with var BN-2 and 1697 :< Pennisetum purpureum.
Sanghi and Raj (1983) studied the performance and
phenotypic stability in pearl millet and Napier hybrids in
India. Twelve hybrids of Napier were tested for forage
yield during 1979-80 in a replicated randomized block
design. Napier breed-21 gave the highest dry matter yield
of 38,592 kgjha whereas Pusa Giant gave a yield of 21,584
kg/ha in 16 cuts. They have stated that NB-21 possessed the
highest stability of performance and. responded to better
environments.
Chemical Cornposi tion of Napier Hybrids. Several
workers have reported that the crude protein content of
Napier hybrids was 8 to 11% (Goonawardene and Appadurai,
1971; Kothandararnan and Dhanapalan Mesi, 1973; Nooruddin and
Roy, 1975; Talpada et al., 1978). Daftardar and Zende
(1968) reported that crude protein contents ranged from
22.8% in young, 14-d-old growth to 5.3% in 72-d-old growth
of Pusa Giant Napier. According to Goonawardene and
Appadurai (1971), the mean crude protein percentage in Pusa
Giant Napier increased with age up to 20 d and declined
thereafter. The highest crude protein obtained was 22.1% at
20-d interval and 12.2% at 60 d was the lowest.
Kothandaraman and Dhanapalan Mosi (1973) reported that
16
the crude protein in Pusa Giant Napier var. Alamadhi and
I.A.R.I. was 6.5 and 11.1%, when cut at the mid-vegetation
stage, and the crude fiber values were 27. 1 and 25. 8%,
re spec ti vely. Kakkar and Kochar ( 1973) reported that the
crude protein content in NB-21 and Pusa Giant Napier
decreased with the season (Summer> Monsoon> Autumn) while
a reverse pattern was observed for the cellulose content.
Crude protein values for NB-21 were 11.5, 10.3 and 5.1% for
Summer, Monsoon and Autumn seasons, respectively. Nooruddin
and Roy (1975) reported that the mean crude protein and
crude fiber contents in Pusa Giant Napier were 6. 5 and
22.6%, respectively, when grown in India, however, they did
not indicate the stage of growth. In another trial, which
was conducted in India, they reported that the crude protein
and crude fiber in Pusa Giant Napier were 6. 46 and 24. 6%,
respectively, at the flowering stage (Nooruddin et al.,
1977).
Talpada et al. (1978), with NB-21, reported that the
mean crude protein of dry matter was 5.8% and the mean crude
fiber was 29. 57% when cut at 40 to SO d of age. Kishan
Singh and Neelakantan ( 1982) reported that the total N in
the fresh herbage of hybrid Napier fodder was 1.7% and the
water-soluble carbohydrate content was 4.3%. Chauhan (1983)
working with NB-21 fodder reported that the mean crude
protein of dry matter was 11.1, 9.6, 7.2 and 6.8% when cut
17
at 45-, 75-, 105- and 120-cm in height at harvest,
respectively.
Digestibility of Naoier Hybrids. Lansbury (1959)
reported that the dry matter digestibility of Bana grass,
which is a cross between Pennisetum typhoideum and
Pennisetum purpureum was 59.0% when the grass was cut during
the dry season, at height of 2. 5 to 3 m tall. They also
indicated that the appearance of forage was rather dry and
stemmy but bullocks and sheep readily ate all except the
toughest sterns.
Dry matter digestibility in hybrid Napier was reported
by Pritchard (1971) to be 65.6% for the leaf and 58.4% for
the stem plus leaf sheaths. The nutritive value of Napier
grass silage (23.8% dry matter) was determined with wethers
by Melotti et al. ( 1971). Digestibility coefficients were
62. 6%, 49%, and 68. 3% for dry matter, crude protein and
crude fiber, respectively. Raju et al. (1975), working with
five Napier hybrids, reported that the cellulose
digestibilities of fodders were 52.0, 50.9, 50.4, 48.9 and
44.2 for PGN, NB-5, NB-21, EB-4 and NB-17, respectively.
Nooruddin et al. (1977) reported that the dry matter
digestibility of Pusa Giant Napier silage was about 50.01%
when harvested at the flowering stage.
Talpade et al. (1978) found that average organic matter
digestibility (dry basis) of NB-21 green forage was about
18
63. 9% at 40 to 50 d of age and average organic matter
digestibility of silage was 63. 9% at 50 to 60 d of age.
Furthermore, they found that the organic matter
digestibility of hay from NB-21 was 59.6% at 50 to 60 d of
age. From these data, they suggested that NB 21 fodder as
green forage or silage, was superior to the hay form. They
also have suggested that the poor digestibility might be due
to more lignification in hay. Chauhan (1983) reported that
the dry matter and crude protein digestibility of NB-21
decreased with the maturity. Values for dry matter
digestibility were 57.5, 53.7, 49.3 and 47.5% and crude
protein digestibility was 55.7, 48.9, 42.5 and 36.5%. for
45-, 75-, 105- and 120-cm in height at harvest,
respectively.
Silage Additives
The main objective of the use of additives is to ensure
that lactic acid bacteria dominate fermentation, resulting
in a well-preserved silage.
acids have been used with
A variety of feedstuffs,
many different silages
and
in
temperate countries and the use of these silage additives
must be based not only on the results of scientific
research, but also the availability and economy of these
materials. Silage additives can be classified into four
main categories (figure 3) (McDonald, 1981).
I- I . ·c1111c11tatio11 stimul.ints
I llactcrial Cad,ohy<lrate cultures sourcrs•
Lactic acid badcria
<.ilucose Sucrose l\lolasscs Cereals Whey Beel pulp Citrus pulp Potatoes Ccllulases
F lg. 3. Classification of silage additives
Silage Additives
I Fer men tat iun
inhibitors
Acid~ Others
Acrohic dclerioratiun
inhibitotS
Nutrients•
·----------·-·------------·----------------------------Mineral acids Formic acid Acetic ndd Lactic acid Ucnwic acid Acrylic acid Ulycollic acid Sulphamic acid Citric iicid Sm hie acid
For,naldchydc I 'a ra formaldch ydc Smliu111 nitrite Sul1ihur dimide Sodium metabisulphite Ammonium hisulphalc Sodium chlm ide Aul ihiotil-s Carhon dioxide Carbon hisulphide I lc~amc th ylc 11ctct ramine llr onopol Sodium hydroxide
Propionic aciLI Caproic acid Sor hie acid l'inrnricin Ammonia
Urea Ammonia lliuret Minernls
• l\losl sulislnncc~ listc,I under c~1hohy,lra1c so111ccs can nlso he lislcd unilcr 11uliie11ls
McDonald (1981).
t--'
'°
20
Tropical forages are low in water-soluble carbohydrates
(Catchpoole and Henzell, 1971; Wilson and Ford, 1973; Noble
and Lowe, 1974) which are necessary for good fermentation
(Wilson and Ford, 1973; Wilkinson and Phipps, 1979).
Research in temperate regions has shown that additions of
carbohydrate sources have resulted in lactic acid
fermentation by increasing water-soluble carbohydrates,
resulting in well preserved silage. Source of carbohydrate
could be from glucose, sucrose or some other source as
indicated by McDonald (1981), but the final objective is to
stimulate lactic acid fermentation. Two additives which
could be used in Sri Lanka are cassava tuber meal and
coconut oil meal. Formic acid could also be used as a
fermentation inhibitor in making silage but the very high
cost makes it uneconomical under present Sri Lankan
conditions.
Cassava Tuber Meal (4-09-598). Cassava is an important
root crop, which has been cultivated in the tropics for
centuries. Oyenuga (1961) reported that the cassava plant
is capable of providing the highest yield of energy per unit
of land, about 13 times more than for corn (Zea mays L.).
Varon (1968) reported that the fresh tuber yields of cassava
vary from 3 to 45 metric tons/ha and this variation is
associated with the differences in varieties, agronomic
practices and environmental conditions under tropical
21
conditions.
Cassava tuber meal is an energy source with a nitrogen-
free-extract content of about 90% (Oke, 1978) consisting of
80% starch and 20% sugars (Vogt, 1966). According to
Johnson and Raymond (1965), amylose and amylopectin make up
99% or more of cassava starch. Several workers have shown
that the primary sugar present in cassava tuber meal is
sucrose, but small quantities of fructose and dextrose also
have been reported ( Seerly et al., 1972). Manicose, a
disaccharide, in cassava tuber meal has been recently
identified by Maghuin-Rogister ( 1968). Table 1 shows the
proximate composition of cassava tuber meal.
Alternative uses of cassava tubers, such as human food,
fuel-alcohol production and animal feed, have been
increasing in importance during the past few years but its
use as an additive for silage making has not been
researched. Cassava tubers are commonly harvested at 9 to
12 mo of age, processed and sun-dried on concrete floors
(Gomez and Valdivieso, 1983b). Cassava tubers processed as
chips, pellets or powder and could be used for silage
preservation and animal production.
Coconut Oi 1 Meal ( 5-01-572). Coconut oil meal (COM),
the residual product after oi 1 extraction from the dried
endosperms of coconuts is available in most tropical
countries, especially in Sri Lanka. It is used as a protein
TABLE 1. COMPOSITIONa OF CASSAVA TUBER MEAL
Crude Ether Reference and location protein extract
Crude fiber
Nitrogen free
Ash extract
--------------------%-----------------~------Vogt (1966) - Congo 2.1 .5 1. 7 1.5 91+. 2
Olson et al. (1969) - Brazil 3.6 .4 3.0 1.0 92.0
Fetuga and Oluyemi (1976) - Nigeria 2.2 .5 2.2 2.7 92.4
Khajaret et al. (1979) - Thailand 2.8 . 3 4.0 2.0 90.8
Gerpacia (1979) - Philippines 2.5 1.0 6.1 3.1 87.3
Ravindran et aL (1982) - Sri Lanka 2.9 1.4 5.0 2.3 88.4
a Dry basis
N N
23
supplement for animals in the tropics. The variations in
composition are apparently related to the methodd of
extraction
nutrients.
which influences the
Creswell and Brooks
digestibility of the
(1971a) reported that
coconut oil meal contains a digestible energy value of 3.6
kcal/g. Table 2 shows the proximate composition of coconut
oil meal. Owusu-Donfer (1970) in Ghana reported that the
carbohydrate-not-cellulose content of coconut oil meal was
41.69% on dry matter basis.
Fermentation Process Involved in Ensiling Tropical Forages
Silage making is not a common practice among livestock
farmers in tropical areas, however, on government
agricultural stations, silage has been made with varying
success and with varying capital outlay in towers, clamps,
pi ts and trenches. Several research workers have reported
the characteristic features of silages made from tropical
herbage plants (Miller et al., 1963; 1966; Catchpoole, 1965;
1966; 1968; Catchpoole and Williams, 1969; Catchpoole and
Henzell, 1971; Tosi, 1973; Xande, 1978). According to these
workers, the factors responsible for preservation of silage
in the tropics are not known, however, they have concluded
that the production of high concentrations of lactic acid is
not important.
Ensiling is the conservation of forage crops by
controlled anaerobic fermentation of water-soluble
Refereuce and location
Owusa-Domfeu et al. (1970) - Ghana
Cresswell a11d Brooks (1970) - Honolulu
Grieve (1966) -Triuidad
Ravindran et al. (1982) -Sri Lanka
a Dry basis
TABLE 2. COMPOSITIONa OF COCONUT OIL MEAL
Crude protein
Ether extract
Crude fiber Ash
Nitrogen free
extract
-------------------------- % --------------------------
25 .5 9.3 6.Y
20.9 5.8 10.5 6.5 46.2
23.7 8.3 16.7
21.8 9.4 21.5 6.5 40.8
Gross energy
~
kcal/g
4.5
N 4.2 ~
4.7
25
carbohydrates by microorganisms within the ensiled mass to
produce organic acids, mainly lactic acid ( Barnett, 1954).
The production of these acids reduces the pH of the medium
to 4. 5 or less, and the silage remains stable as long as
anaerobic conditions are maintained. The quality of
preserved silage is assessed by chemical standards and
feeding trials. According to Carpintero et al. (1969), a pH
value of 4. 2 or below, butyric acid concentration of less
than .2% and arnmoniacal nitrogen content of less than 11% of
the total nitrogen, characterize well preserved silage.
According to Langston et al. (1958), as cited in Catchpoole
and Henzell ( 1971), lactic acid content in well preserved
silage can be between 3 and 13%, dry basis. However, these
standards were based on experience with unwilted temperate
forages, but not with wilted temperate forages or tropical
forages.
According to Catchpoole and Henzell (1971), "Standards
that measure anaerobic decomposition, such as concentration
of NH3 -N and butyric acid, should be applicable to all types
of silage but standards based on pH and lactic acid have
little or no value when the preservation is not due to
lactic acid fermentation, as in silage made from wilted
temperate forages." Therefore, the application of these
standards to tropical forage silages are of doubtful value.
Catchpoole (1966), with Setaria sphacelata and Chloris
26
gayana in Queensland, reported that the amount of soluble
carbohydrates available in these tropical grasses was too
low to ensure satisfactory production of lactic acid when
they were ensiled.
Catchpoole ( 1966) found that the amount of molasses
required to produce lactic acid silage from Setaria
sphacelata was much higher than the amount needed for
temperate grasses. According to his study, the percent
sugars as glucose in vegetative Setaria sphacelata ranged
from 5.2 to 7.9, dry basis, as compared to 4.1 to 4.9 at
heading stage. At the vegetative stage addition of 4%
molasses increased the percent lactic acid in silage from .9
to 2.3, dry basis, when compared with the control, but,
there was no change in pH. At the heading stage, the lactic
acid content increased from .4 to 4.3%, dry basis, and pH
was decreased from 4.7 to 4.1 with addition of 4% molasses.
He suggested that molasses did not stimulate strong lactic
acid accumulation in ensiled Setaria sphacelata grass,
however, higher applications would be expected to increase
the amount of lactic acid.
Miller et al. (1963; 1966), in U.S.A., reported that
the ensiling character~stics of Coastal bermudagrass were
different from those of temperate forages. They obtained
very low levels of lactic, acetic and total organic acids in
bermudagrass compared with temperate forage silages.
27
Catchpoole (1968) reported that the water-soluble
carbohydrate contents decreased with maturity in early
growing season (November-December) and mid growing season
(January-February)-cut Setaria sphacelata grass, whereas the
reverse happened in late growing season (March-Apri 1) -cut.
The water-soluble carbohydrate contents were less than 6%,
dry matter, for all the samples. All silages had pH values
above 4. 4 and lactic acid contents were very low, ranging
from 1.9 to 14.9 m-equiv/100 g of dry silage.
Catchpoole and Williams (1969) considered the general
patterns in silage fermentation in two subtropical grasses,
namely, Setaria sphacelata and Chloris gayana and concluded
that silage with a relatively high concentration of acetic
acid could be expected under subtropical conditions, whereas
high lactic acid silage could be seen under temperate
conditions. Furthermore, they showed that the acetic acid
silage was extremely stable under subtropical conditions,
similar to lactic acid silage in temperate regions. They
suggested that lactic acid would be produced under
subtropical conditions, but it is usually fermented further.
Addition of soluble carbohydrates could stabilize the lactic
acid fermentation in these grasses, but high levels of sugar
would be needed.
According to Catchpoole and Henzell (1971) some of the
tropical forage species could produce stable silages without
28
additives. The preservation technique of these silages did
not include the production of high concentrations of lactic
acid and the factors responsible for this have not been
identified. However, t~ey suggested that this may be
related with the high dry matter content of these tropical
forages, thereby reducing the water activity or increase in
osmotic pressure of the plant material.
Tosi (1973) reported that the main problem of ensiling
tropical forages was their low soluble-carbohydrate content
( 5. 9-11. 4%) in the dry matter, which was insufficient for
the development of an intense lactic fermentation, favoring
the production of acetic silages. According to his results
lactic acid of these silages ranged from 1.1 to 2. 4% and
acetic acid from 2.5 to 4.0%, dry basis. On the other hand,
Napier grass silage had relatively high lactic (6. 7%) and
low acetic (1.8%) acid. He concluded that the addition of
30% sugar cane was insufficient to promote the lactic acid
bacteria fermentation, because the major problem of the
forages was the low soluble carbohydrate content.
Farias and Gomide (1973) studied the effect of wilting
and of cassava meal addition on the characteristics of
silage from Napier grass cut at various dry matter contents.
Ensiling Napier grass with a dry matter content of ~ 23%
reduced dry matter losses and lactic acid content. Wilting
also reduced dry matter losses, especially when grass was
29
cut when its dry matter content was lowest; it also
increased silage protein content but reduced pH and lactic
acid content. The addition of cassava meal gave silage with
high dry matter and soluble carbohydrate contents, reduced
dry matter losses ar.d increased in vitro dry matter
digestibility.
Effect of growth stage, wi 1 ting and the addition of
cassava scrapings on the nutritive value of Napier grass
silage was studied by Ferreira et al. ( 1974:) . They
concluded that the maturity stage of the herbage had no
effect on dry matter intake or N balance but the addition of
ground cassava scrapings before ensiling increased dry
matter
matter
intake,
intake
digestibility.
dry
and N
matter digestibility,
balance, but reduced
digestible dry
crude protein
Aguilera ( 1975), with Napier grass in Cuba, reported
that the fermentation period studied could be divided into
two stages, the first with lactic acid characteristics
(30-d) and the second with clostridial characteristics
(60-d). It was suggested that acetic acid rather than
lactic acid was the main preservative in Napier grass
silage.
Hamilton and co-workers (1978), working with Nandi
Seteria grass, stated that when the dry matter content was
about 32. 2%, silage fermentation was mainly lactic acid.
30
Xande (1978) reported that criteria of preservation quality
for temperate grasses (pH, lactic acid content, organic
acids) do not apply for tropical grasses because of a
different fermentation pathway from lactic acid. He stated
that the important factor governing the nutritive value of
tropical silage was its voluntary intake which was in turn
related to the low N content. It was suggested that this
could be improved by including legumes with the ensi led
grass.
Dominguez and Hardy (1981) studied the effects of
cutting age and final molasses additives on the quality of
Pangolo grass (Digitaria decumbens, Stent) silage. The pH
was lower for the longest cutting interval (4.9 vs 3.6 for
4- and 7 wk, respectively) and descended significantly with
molasses supplementation ( 4. 2, 4. 1 and 4. 0 for O, 1 and 2%
molasses, respectively). Lactic acid differed significntly
between cutting ages (.19 and 3.01%, dry basis, for 4 and 7
wk, respectively) but there were no differences between the
molasses levels. Total volatile fatty acids were
significantly lower for grass at 7 wk of age (4.5, 2.7 and
3.5%, dry basis) and contrasted with the values obtained at
4 wk of age (16.6, 18.1 and 11.9%, dry basis, for 0, 1 and
2% molasses, respectively). It was concluded that the
longest cutting interval improved dry matter and the
fermentati ve characteri sties of silage. Thus, it was not
31
necessary to add molasses to Pangola grass silage cut at 7
wks.
In another study, Dominguez and Elias ( 1981) studied
the effects of age at cutting Coast Cross No. 1 bermuda
grass (Cynodon dactylon L. Pers), the inclusion of urea and
different levels of molasses in silage quality. Dry matter
digestibility differed between cutting ages (48.4 vs 45.2%)
of 6 and 8 wk but pH was not affected. Acetic acid differed
between treatments for levels of molasses and urea with
respect to the control. They concluded that the 6 week old
coast cross bermudagrass silage could be improved by using
lower levels of urea (less than 1%) and 3% molasses.
Kishan Singh and Neellakanthan (1982) studied the
chemical composition of hybrid Napier silage in India.
According to their results, pH, lactic acid, acetic acid and
butyric acid values were 4.9, 1. 3%, 8.5% and 2.1%,
respectively. They reported that initial silage sugars were
4. 3%, whereas silage sugar content after 20 d was 2. 3%
indicating 2.03% sugar degradation. In another study, Singh
and Pandita (1984) studied the fermentation characteristics
of Napier grass silage. They obtained values of 4.8, 4.5
and 4.2 for pH; 2.7, 2.5 and 2.3% for acetic acid; 1.02, .30
and . 21% for butyric and 1. 2, 6. 6 and 6. 9% for lactic acid
when the storage period was 30-, 60- and 120-d,
respectively.
32
In summary, when tropical grasses are ensiled without
wilting, they are likely to ferment during ensiling to give
relatively high contents of acetic acid unless additional
fermentable carbohydrates are added.
CHAPTER III Journal Article I
ENSILING CHARACTERISTICS OF TWO TROPICAL FORAGES
Summary
Research was conducted in Sri Lanka to study the
effects of growth stage, chopping length and additives on
ensiling characteristics of Guinea-'A' (Panicum maximum,
Jacq - Ecotype 'A') and NB-21 (Pennisetum purpureum, Schumac
x Pennisetum americanum, L.). The forages were harvested 1,
2 and 3 wk after clipping, chopped and ensiled in small
laboratory silos alone or with additions of cassava tuber
meal, coconut oil meal and formic acid. Cutting grass at 1
wk increased (P<.05) acetic and lactic acid of silage,
compared to 3 wk. Addition of cassava tuber meal and
coconut oil meal decreased (P<.05) pH, and acetic acid and
increased lactic acid (P<.05) of silage, compared with the
control. The effects were greater for cassava tuber meal.
Addition of formic acid had no significant effect on
ensiling characteristics compared to the control. In a
second study 3 wk growth of Guinea-'A' grass was chopped in
three lengths, namely, 1. 5, 7. 5 and 15 cm and ensi led in
small silos. Lactic and acetic acid of silage increased
(P<. 01), whereas dry matter loss and pH decreased (P<. 05)
with fineness of chop. In a third study, 2 and 3 wk growth
of Guinea-'A' were harvested and ensiled in 210 liter metal
drums, chopped or unchopped. Cutting grass at 2 wk
33
34
decreased (P<.01) pH and increased (P<.01) lactic acid
compared to cutting at 3 wk. Dry matter loss was · lower
(P<. 01) and dry matter content of the silage was higher
(P<.06) for chopped silage. Chopping decreased (P<.05) the
pH and increased lactic and acetic acid of silage. Results
show that the silages made in this study had more acetic
acid than lactic acid, except when cassava tuber meal was
added.
(Key Words: Tropical Forage, Silages, Guinea Grass, NB-21,
Additives, Ensiling, Chopping Length.)
Introduction
The major problem which hinders expansion of ruminant
production in Sri Lanka and other tropical countries is lack
of good quality pasture throughout the year. Seasonal
rainfall in most parts of Sri Lanka results in a fluctuating
supply of pasture, thus highlighting the urgent need for
forage conservation for periods of short feed supply. There
are various advantages of making silage over making hay in
Sri Lanka, a humid tropical country.
Silage making is not a common practice among livestock
farmers in tropical areas and the fermentation
characteri sties of these tropical forage silages have not
been identified satisfactorily. Several research workers
have reported that fermentation of these silages do not
result in production of large concentrations of lactic acid
35
(Miller et al., 1963; 1966; Catchpoole, · 1965; 1966; 1968;
Catchpoole and Williams, 1969; Catchpoole and Henzell, 1971;
Tosi, 1973; Aguilera, 1975; Xande, 1978). They have
suggested that acetic acid rather than lactic acid is the
main preservative in tropical forage silages.
Generally, tropical forages are poor in water-soluble
carbohydrates which are important for ensi ling. In
temperate forages additions of cereals and molasses have
resulted in lactic acid fermentation from increasing water-
soluble carbohydrates (McDonald, 1981). Manioc (Manihot
esculenta, Crantz) tuber meal and coconut (Cocos nucifera,
L.) oil meal could be used to supply soluble carbohydrates
since they are readily available in Sri Lanka.
The objectives of the present study were to investigate
the ensiling characteristics of Guinea-'A' and NB-21 cut at
different intervals with different additives. Furthermore,
the effect of chopping length on ensiling characteristics of
Guinea-'A' grass was studied.
Materials and Methods
Small Silo Study. Two fodder grasses, namely
Guinea-'A' and NB-21, established in 1980, were grown at the
Mawela Farm, Peradeniya (Longitude 80° 29'E, latitude 7°
13'N, elevation 485m}, Sri Lanka in a reddish brown
latasolic soil with a pH value of 5.8 for the Guinea-'A' and
4.9 for the NB-21 plot areas. Plots measuring 17.4 x 2.8 m
36
for Guinea-'A' and 10 x 8.2 m for NB-21 were arranged in a
randomized block design with three replications.
Phosphorous as triple super-phosphate and N as urea were
applied at the rates of 112 and 168.5 kg/ha, respectively,
uniformly to the entire area at the beginning of the trial
(May, 1983). Guinea-' A' plots were irrigated during the
trial. Each forage was harvested at three stages of plant
growth, corresponding to l, 2 and 3 wk after cutting the
foliage. The grasses were cut uniformly to a height of 12.5
cm from ground level, at 1 wk intervals, prior to the
commencement of the trial so that all plots were harvested
on the same day for ensiling.
At harvest, Guinea-'A' and NB-21 were chopped and
ensiled alone or with three additives, cassava tuber .meal,
coconut oil meal and formic acid in May, 1983 ( table 3).
Thus, within each forage plots were arranged in a 3 x 4
factorial. The following amounts of additives were mixed
with grasses at the time of ensiling: 5% cassava tuber
meal, wet basis; ~~ coconut oi 1 meal, wet basis; and 3%
formic acid, dry basis. Fourteen kg of each mixture were
prepared by adding the additive to the grass in polyethylene
bags and mixing for 5 to 8 min. As grass and additives for
each mixture were weighed, a sample of grass was taken.
Six laboratory silos, each containing 2 kg, were
prepared from each mixture. Four samples of the initial
37
TABLE 3. COMPOSITION OF CASSAVA TUBER MEAL AND COCONUT OIL MEAL USED IN SMALL SILO STUDY
Component
Dry matter • a. Crude protein
a Ether extract Crude fibera Asha
a Water-soluble carbohydrates
a Dry basis.
Cassava Coconut tuber oil meal meal
% %
90.6 89.1 3.8 19.6 .s 12.1
2.3 9.3 2.1 9.0
72.1 17.6
38
mixtures were collected and frozen for subsequent analysis.
The mixtures to be ensiled were firmly packed into 3 liter
cardboard cylinders double lined with two polyethylene bags.
The bags were sealed· individually, being careful to expel
the air above the packed material before sealing. Silos
were weighed before and after addition of the mixtures.
After 60 d at room temperature silos were weighed and
opened and the top 5 cm of ensiled material were discarded
prior to sampling. Water extracts of the initial and
fermented mixtures were prepared by homogenizing 25 g with
225 ml of distilled water in a 1 liter jar in a Waring
blender at full speed for 2 min. The homogenate was
filtered through four layers of cheesecloth and the filtrate
was used for measuring of pH (electrometrically), volatile
fatty acids (VFA) (Markham, 1942; Erwin et al., 1961),
lactic acid (Barker and Summerson, 1941, as modified by
Pennington and Sutherland, 1956) and water soluble carbohy-
drates (Dubois et al., 1956, as adapted to corn plants by
Johnson et al., 1966).
Kjeldahl nitrogen was determined on initial mixtures,
cassava tuber meal, coconut oil meal and silages (A.O.A.C.,
1980). Dry matter of initial samples and silages was
determined by drying 200 g samples in an Unitherm oven at 55
C for 24 h. These samples were allowed to air equilibrate
and dry weights were recorded. All initial samples were
39
ground to pass 1 mm sieve and analyzed for dry matter (DM),
neutral detergent fiber (NDF) (Van Soest and Wine, 1967),
acid detergent fiber (ADF) (Van Soest, 1963), lignin and
cellulose (Van Soest and Wine, 1968).
In another study, 3 wk growth of Guinea-'A' grass was
hand chopped in three lengths, namely, 1. 5 (fine), 7. 5 and
15 cm and ensiled in small laboratory silos in May, 1983.
These forages were the same as those used in the previous
study. These silos were opened after 60 d and the same
parameters were determined as described previously.
Large Silo Study. An established stand of Guinea-'A'
grass was used at Meewatura Farm, Peradeniya, Sri Lanka, in
a reddish brown latasolic soil with a pH value of 5. 3.
Plots measuring 20 x 30. 5 m were arranged in a randomized
block design with five replications. Phosphorus as triple
super-phosphate and N as urea (112 and 168.5 kg/ha,
respectively) were applied uniformly to the entire area at
the beginning of the trial. All plots were hand cut
uniformly to a height of 12.5 cm from ground level, at 1 wk
interval, prior to the commencement of the trial.
The forage was harvested at two stages of plant growth,
2 and 3 wk after foliage regrowth in May, 1983. The herbage
was hand cut to 12.5 cm above ground level and five
replicates were composited and divided into two equal
portions. One portion of the material was chopped and
40
ensiled and the other portion was ensiled without chopping.
Several samples of the grass were taken while filling each
silo for subsequent analysis. The grass for ensiling was
firmly packed into 210 liter steel drums double lined with
polyethylene bags. An attempt was made to remove as much
air above the ensiled mass as possible before each
polyethylene bag was sealed.
After 60 d of fermentation in an open shed, each silo
was opened and the top 5 cm of ensiled material was
discarded. Samples were taken and frozen for subsequent
chemical analyses. Procedures used for determination of
fermentation characteristics, crude protein and cell wall
fractions of the initial and silage samples were the same as
those for the small silos. Silos were weighed before and
after addition of the material and after ensiling.
Statistical Analysis.
performed using the analyses
Statistical analyses were
of variance by the general
linear model procedure of SAS (1982). For the first small
silo study, comparisons were made to test linear and
quadratic effects of stage of growth; control vs additives;
formic vs cassava tuber meal and coconut oil meal; cassava
tuber meal vs coconut oil meal; and interactions. For the
second small silo study, two contrasts were made to compare
1. 5 cm vs 7. 5 and 15 cm and 7. 5 cm vs 15 cm. Cornpari sons
were made for the large silo study to test 2 wk vs 3 wk,
41
unchopped vs chopped treatments and the interaction.
Results
Small Silos. The composition of the initial samples
after different periods of growth are presented in table 4.
Lengthened growth period linearly increased (P<.01) dry
matter of Guinea-'A'. The mean crude protein percentage in
Guinea-' A' tended to increase with age up to 2 wk, but
declined thereafter. The water-soluble carbohydrate content
of NB-21 was similar for forages cut after 1 and 2 wk
growth, but was increased sharply in the forage after 3 wk
growth. The effect is best described by a quadratic effect
(P<.01).
Additives increased (P<.01) dry matter content of pre-
ensiled mixtures of Guinea-A when compared to the control
(table 5). Addition of cassava tuber meal and coconut oil
meal increased ( P<. 01) the percentage dry matter of pre-
ensi led mixtures of Guinea-'A' and NB-21 more than addition
of formic acid. Addition of coconut oil meal increased
(P<.01) the mean crude protein percentage of the pre-ensiled
Guinea-'A' and NB-21 mixtures more than the cassava tuber
meal. This is due to the higher crude protein content of
coconut oil meal, 19.6%, compared to 3.8% for cassava tuber
meal ( table 3) .
The pH of the post-ensiled material was decreased
TABLE 4. COMPOSITION AND FERMENTATION CHARACTERISTICS OF GUINEA-'A' AND NB-21 AS AFFECTED BY
OF GROWTH, SMALL SILO STUDY
Component
Dry matter, %a Crude protein, %b Cell wall fractions, %b
Neutral detergent fiber Acid detergent fiber Cellulose llemicellulosec Lignin b d
Water-soluble carbohydrates'
1
16.3 14.1
69.9 41. 9 30.4 28.1
6.5 6.7
3 Linear effect (P < .01) for Guinea-'A'. bDry basis.
cLinear effect (P< .05) for Guinea-'A'. dQuadratic effect (P < .01) for NB-21.
Period of growth, wk, Guinea-'A' 2 3 SE
19.4 19.8 .28 15.1 13. 9 .55
70.2 71. 9 .75 39.4 41.0 .71 29.2 30.8 1.10 30.8 30.9 .86
6.6 6.7 • 27 7.1 7.6 .33
OF INITIAL SAMPLES STAGE
Period of growth, wk, NB-21
1 2 3 SE
15.6 15.5 17.7 .59 24.8 24.1 22.9 .60
66.9 65.4 65.6 .90 ~ N
34.4 33.1 32.5 .63 25.5 24.9 24.6 .48 32.6 32.2 33.1 .81
5.5 5.5 5.8 .33 8.2 8.7 11.4 .47
TABLE 5, COMPOSITION OF PRE-ENSILED MIXTURES OF GUINEA-'A' AND NB-21 AS AFFECTED BY ADDITIVES, SMALL SILO STUDYa
Additive Cassava Coconut Formic
Grass Component None tuber meal oil meal acid
Gui.nea-'A' Dry matter, %b,c 17.7 20.6 21. 2 18.8 C d e Crude protein,% ' ' 13.9 13.4 15.5 ]2,6
NB-21 Dry matter,% C ]6,3 18.4 ]8,4 16.0
Crude protein, %d,e 18.1 17.8 19.6 18.3
a Averaged over growth periods.
bNone vs additives (P < .01) for Guinea-'A'.
cFormic acid vs cassava tuber meal and coconut oil meal (P < .01) for Guinea-'A' and NB-21. d Dry basis.
eCassava tuber meal vs coconut oil meal (P < • 01) for Guinea-' A'.
SE
.54
.54
-"' w .48
.52
44
(P<.01) for forages cut after 2-wk growth, but was increased
in the forage after 3-wk growth for Guinea-'A' and NB-21,
however, the differences were small (table 6). Lengthened
growth period linearly increased (P<.01) the water-soluble
carbohydrate content of the pre-ensiled Guinea-'A' and NB-21
mixtures. Ensiling decreased the water-soluble carbohydrate
content of the post-ensiled mixtures of Guinea-'A' and NB-21
almost by one half or more. There were no significant
differences in water-soluble carbohydrate content among the
three growth periods of NB-21. Amount of lactic acid
present in post-ensiled mixtures was highest for 1 wk growth
for Guinea-' A' and lowest for 3 wk. Growth period had a
linear effect (P<.01) on lactic acid content of Guinea-'A'.
Fermentation characteristics of pre- and post-ensiled
mixtures as affected by additives are presented in table 7.
Addition of formic acid decreased (P<.01) the initial pH to
4.5 and 4.2 in Guinea-'A' and NB-21, respectively. The pH
of the material decreased by one or more uni ts in all
treatments following ensiling, except for formic acid
treated silage. Addition of cassava tuber meal and coconut
oil meal had a more pronounced effect in decreasing the pH
of the post-ensiled material than formic acid. Addition of
cassava tuber meal decreased ( P<. 01) the pH of the post-
ensi led material more than coconut oil meal.
Water-soluble carbohydrate content of pre-ensiled
TABLE 6. FERMENTATION CHARACTERISTICS OF PKE- AND l'OST-ENSILED MIXTURES OF GUINEA-'A' AND NB-21 AS AFFECTED BY STAGE OF GROWTH,
SMALL SILO STUDY a ·
Growth period, wk,
Item 1
pH Pre-ens ile<l b 6.2 Post-ensile<lc,d 5.0
Water-solublebctrbohydrates, %e 5.6 Pre-ensiled b
Post-ensiled 3.1
L . "d % e actic ac1 , " Post-e11siled h 2.5
a Averaged over additives.
bLinear effect (P < .01) for Guinea-'A'. c Quadratic ef feet (P < . 01) for Guinea-' A' • dQuadratic effect (P <.01) for NB-21. e Dry basis. fLinear effect (P < .01) for NB-21.
Guinea-'A' 2 3 SE
6.0 5.9 .09 4.8 4.9 .02
9.1 10.0 • 72 3.9 4.5 .20
1.8 1.5 .13
Growth period, wk, NB-21 -1 2 3
5.9 5.8 5.9 4.9 ,, .8 5.1
11.8 12.2 14.4 5.2 4.9 4.5
3.0 3.1 2.7
SE
.04
.05 p. VI
.50
.42
.29
TABLE 7. FERMENTATION CHARACTERISTICS OF PRE- AND POST-ENSILED MIXTURES OF GUINEA-'A' AND NB-21 AS AFFECTED BY ADDITIVES, SMALL SILO STUDYa
Grass
Guinea-'A'
NB-21
Item
pH Pre-e11siledb,c Pust-ensiledb,c,d
Water-soluble carbohydrates, %e Pre-ensiledb,f,g Post-ensiledc,d
Lactic acid, %e Pust-ensiledb,c,d
pl! b Pre-ensiled ~c,dd Post-ensiled ,c,
Water-soluble c3rbohydrates, %e Pre-ensiledb, Post-ensiledd
L . 'd %e act1.c ac1. , o b C d Post-e11siled ' '
a bAveraged over growth periods.
None
6.7 5.3
6.3 3.6
.11
6.6 5.3
9.9 4.3
.75
Additives Cassava
tuber meal
6.3 4.2
11.0 5.9
7.1
6.5 4.2
16.0 6.4
6.95
Coconut oil meal
6 .5 · 5.1
8.3 2.8
.45
6.2 4.8
12.3 3.8
3.4
Formic acid
4.5 5.1
7.3 2.9
.10
4.2 5.3
12.9 4.8
.61
Control vs additives (P< .01) for Guinea-'A' and NB-21. ~Formic acid vs cassava tuber meal and coconut oil meal (P< .01) for Guinea-'A' and NB-21. 'Cassava tuber meal vs coconut oil meal (P < • 01) for Guinea-' A' and NB-21. ;Dry basis.
Formic acid vs cassava tuber meal and coconut oil meal (P < • 05) for Guinea-' A'. gCassava tuber meal vs coconut oil meal (P < .05) for Guinea-'A'.
SE
.11
.03
.83
.23
.15
.05
.06
.58
.47
. 35
"' °'
47
mixtures were increased (P<.01) with the addition of
additives ( table 7) . The effect was especially prominent
with the addition of cassava tuber meal. Cassava tuber meal
is a source of energy with a nitrogen-free extract content
of about 90% ( Oke, 1978) which consists of 80% starch and
20% sugars (Vogt, 1966). According to the analysis done in
this study, it had about 72% water-soluble carbohydrate
content (table 3). Coconut oil meal also increased (P<.01)
the water-soluble carbohydrate content of the pre-ensiled
mixture, when compared to the control ( table 7) . Water-
soluble carbohydrate content of post-ensiled mixtures were
less than half of the pre-ensiled mixtures (table 7). The
post-ensiled cassava tuber meal mixture contained the
highest water-soluble carbohydrate level.
Addition of cassava tuber meal resulted in the highest
post ensiled level of lactic acid for both grasses. The
higher lactic acid is probably due to the higher water-
soluble carbohydrate of that additive (table 3). The lactic
acid in formic acid treated silages was not increased,
compared to the control.
Coconut oil meal did not have a substantial effect on
lactic acid in Guinea-' A' silage ( table 7). Addition of
coconut oil meal markedly increased the lactic acid content
of the NB-21 silage, but, the effect was much less than
addition of cassava tuber meal.
48
Increasing length of the growth period linearly
increased (P<.01) the percentage dry matter in silages
( table 8). Lengthened growth period linearly decreased
( P<. 01) acetic acid of the Guinea-' A' silages. A similar
trend was observed for NB-21 silages but the effect was
quadratic (P<.01). This may be due to the better packing of
younger material in
fermentation.
the . 1 Sl.-0, thereby enhancing
Table 9 presents the effects of various additives upon
dry matter percentage and VFA concentration in the small
silos.
matter
Additives increased (P<.01) the percentage dry
of silage. However, formic acid did not
substantially change dry matter, compared to control.
Increased lactic acid was involved with lower acetic acid in
silage (table 9). In control and . formic acid treatments,
fermentation of forages produced mainly acetic acid and(or)
propionic acid, and not lactic acid as in the case of most
temperate silages.
As shown in table 10, dry matter content of the grass
used in the chopping length study was 19.8% and crude
protein was 12. 4%, dry basis. The pH of the post-ensiled
mixture was low, compared to pre-ensiled mixture (table 11).
Average post ensi led pH was lower ( P<. 05) for the silage
chopped to 1.5 cm vs 7.5 and 15 cm. A higher (P<.01) water-
soluble carbohydrate content of post-ensiled material was
TABLE 8. EFFECT OF PERIOD OF GROWTH OF GUINEA-'A' AND NB-21 UPON DRY MATTER CONTENT AND VOLATILE FATTY ACID PRODUCTION, SMALL SILOa
Growth eeriod, wk, Guinea-'A' Item 1 2
Dry matter, % b,c 15.80 17.99 Volatile fatty acids, % d
Acetic b, e 5.44 4.19 Prop ionic 2.36 2.61 Isobutyric .73 1.00 Butyric .78 1.17 Isovaleri.c .23 .32 Valerie . 72 .47
aAveraged over additives. hLinear effect (P < .01) for Guinea-'A'. cLinear effect (P < • 01) for NB-21. dory basis. eQuadratic effect (P < .05) for NB-21.
3 SE
17.99 .22
4.03 .26 2.78 .40 1.16 .21
.86 .24
.13 .07
.56 .09
Growth period, wk2 NB-21 1 2 3
12.89 14.59 15.32
5.56 4. 72 4.28 3.90 2.90 2.24
.83 .97 .99
.38 .82 .49 0 .21 .18
.35 . 51 .14
SE
.17
.42
.75
. 38 .i:-
.32 ,o
.07
. ] 4
TABLE 9. EFFECT OF ENSILING VARIOUS ADDITIVES UPON DRY MATTER CONTENT AND VOLATILE FATTY ACID CONCENTRATION, SMALL SILO STUUYd
Grass
Guinea-'A'
NB-21
I tern
Dry matter, %b,c
Volatile fatty acids, %d Aceticb,e Propionic c,e Isobutyri.c b ,c Butyricb,e Isovaleric b, c Valerich,c
Dry matter, %b,c,e
Volatile fatty acids, %d Aceticc Propionic c Isobutyric c Butyric Isovalericb Valericc
None
14.93
5.39 3.03 1.90 1.51
.48 1.09
12.10
5.28 3.93 1.26 1.23
.38
.81
Additives Cassava
tuber meal
19.31
3.49 .98 .11
0 0 0
16.22
3.40 .54 .19 .01
0 0
Cocortut oil meal
19.02
4.62 2.91
.56 1.40
.12
.10
17.09
3.45 1.84
,07 .18 .03 .02
aAveraged over growth periods. b Control vs additives (P < • 01) for Guinea-' A' and NB-21.
Formic acid
15. 77
4.69 3.40 1.25
.83
.29 1.13
11.67
7.30 5.70 2.20
.85
.12
. 53
cFormic acid vs cassava tuber meal and coconut oil meal (P < .01) for Guinea-' A' and NB-21. dory basis. eCassava tuber meal vs coconut oil meal (P < • 01) for Guinea-' A' and 1m-21.
SE
.25
.30 , l+6
.24
.28
.08
. 11
.20
.so
.89
.45
.39
.09
.17
\Jl 0
51
TABLE 10. COMPOSITION OF INITIAL SAMPLES OF GUINEA-'A' GRASS USED IN CHOPPING
LENGTH STUDY - SMALL SILO STUDY
Component
Dry matter Crude proteina Cell wall fractionsa
Neutral detergent fiber Acid detergent fiber Cellulose Hemicellulose Lignin
aDry basis.
Percent
19.8 12.4
70.9 40.2 30.7 30.8
6.1
52
TABLE 11. FERMENTATION CHARACTERISTICS OF PRE- AND POST-ENSILED MIXTURES AS AFFECTED BY CHOPPING LENGTH, SMALL SILOS
pH
Item
Pre-ensiled Post-ensileda
Water-soluble carbohydrates, %b Pre-ensiled Post-ensileda
L . 'd %b act1c ac1. , • Post-ensileda
al.5 cm vs 7.5 and 15 cm (P < .05). b Dry basis.
Chopping length, cm 1.5 7.5 15.0
6.2 6.1 6.2 5.2 5.4 5.4
8.5 8.0 8.9 5.5 3.3 2.6
.15 .06 .05
SE
.04
.04
.73
.73
.03
53
observed for 1. 5 cm forage, compared to 7. 5 and 15 cm.
Chopping the grasses into fine (1.5 cm) particles increased
(P<. 01) lactic acid in the post-ensi led mixture, al though
all values were low.
Chopping the grass into fine (1.5 cm) particles
decreased (P<.05) the percentage dry matter loss compared to
7.5 and 15 cm lengths, although the difference is very
small. Values for dry matter loss were 2.46, 2.67 and 2.76%
for 1.5, 7.5 and 15 cm lengths, respectively.
There was no significant effect of chopping on the
percentage dry matter ( table 12). Acetic acid was higher
( P<. OS) for silage from forage chopped to 1. 5 cm, whereas
propionic acid was higher ( P<. 05) for 15 cm length. The
results show that chopping the grass into fine pieces
decreased the pH and increased the lactic and acetic acid,
and therefore produced a better quality silage than the
other chopping lengths.
Large Silos. Composition of the initial samples of the
silage due to the growth stage is shown in table 13.
Percentage dry matter
(P<.01) than at 2 wk.
content of 3-wk growth was higher
However, growth stage did not have
any significant effect upon the crude protein content or the
cell wall fractions.
Table 14 presents the fermentation characteristics of
pre- and post-ensiled mixtures as affected by the growth
54
TABLE 12. EFFECT OF CHOPPING LENGTH UPON DRY MATTER PERCENTAGE AND VOLATILE FATTY ACID CONCENTRATION - SMALL SILO
Cho:e:eing length, cm Item 1.5 7.5 15
Dry matter, % 15.22 17.28 15.49
Volatile fatty acids, %a Aceticb 5.43 4.00 3.73 Propionicc 2.44 2.04 5.18 Isobutyric 1.21 .88 .95 Butyric 1. 79 2 .10 .31 Isovaleric .59 .47 .17 Valerie 1.00 .49 .68
aDry basis bl.5 cm vs 7.5 and 15 cm (P < .05). c7.5 vs 15 cm (P < . 05) .
SE
.68
.52
.92
.39
. 61
.17
.20
55
TABLE 13. EFFECT OF GROWTH PERIOD ON THE COMPOSITION OF INITIAL SAMPLES OF GUINEA-'A'
GRASS - LARGE SILO
Components
Dry matter, %a b Crude protein,% b Cell wall fractions, %
Neutral detergent fiber Acid detergent fiber Cellulose Hemicellulose Lignin
a2 wk vs 3 wk (P < .OS) b Dry basis.
Growth 2
16.9 13.3
71.4 40.3 30.6 31.0 6.6
Eeriod, wk 3
20.3 12.0
69.8 40.6 31.8 29.2 6.2
SE
.60
.79
.88
.59
.54 1.05
.20
56
TABLE 14. FERMENTATION CHARACTERISTICS OF PRE- AND POST-ENSILED GUINEA-'A' GRASS AS AFFECTED BY GROWTH PERIOD,
pH
Item
Pre-ensileda Post-ensileda
LARGE SILO
Water-soluble carbohydrates, %b Pre-ensiled Post-ensiled
L . "d %b act1.c ac1.., ·a Post-ens1.led
a2 wk vs 3 wk (P < .05) b Dry basis.
Growth period, wk 2 3
6.94 6.63 5.43 5.61
5.02 5.26 4.53 4.05
1.34 .14
SE
.11
.02
.30
.29
.06
57
stage. Differences (P<.05) were observed in pH between the
pre-ensiled 2 wk and 3 wk growth. Ensiling decreased the pH
of the material by more than one unit, and this reduction in
pH was more prominent in 2 wk growth. The post-ensiled pH
for 2-wk growth was lower (P<.01) than for the 3-wk growth.
There were no significant differences in water-soluble
carbohydrate contents in pre-ensi led or post-ensiled
material due to the growth period. However, water-soluble
carbohydrate content was higher in post-ensiled 2 wk than
the post-ensiled 3 wk growth. Ensiling the grass after 2 wk
growth increased (P<.01) the lactic acid, compared to 3 wk
growth (1.34 and .14%).
Chopping decreased (P<.05) pH of the ensiled material
(table 15). The values were 5.64 and 5.40 for unchopped and
chopped silage, respectively. Ensiling of forages decreased
water-soluble carbohydrate, but loss of water-soluble
carbohydrate was less in chopped silage. Data also show
that chopping increased (P<.01) the lactic acid of ensiled
material (table 15).
Interaction between growth period and chopping length
was observed for water-soluble carbohydrate and lactic acid
in the silage. Chopping the grass increased water-soluble
carbohydrate and lactic acid in silage more at 2 wk growth
than 3 wk growth compared to the unchopped grass.
Dry matter loss for 3 wk growth was higher (P<.01) than
58
TABLE 15. FERMENTATION CHARACTERISTICS OF PRE- Ai.~D POST-ENSILED GUINEA-'A' AS AFFECTED BY
CHOPPING, LARGE SILOS
Item
pH Pre-ensiled Post-ensileda
Water-soluble carbohydrates, %b Pre-ensiled Post-ensileda
L . 'd %b act1.c ac1., • Post-ensileda
a Unchopped vs chopped (P < .OS). b Dry basis.
Unchopped Chopped
6.73 6.84 5.64 5.40
4.93 5.36 3.58 4.99
.09 1.39
SE
.11
.02
.31
.29
.06
59
that of 2 wk growth. Values were 11.06 and 11.78% for 2 and
3 wk growths, re spec ti vely. Dry matter loss was lower
(P<.01)
Values
for chopped silage,
for dry matter loss
compared to unchopped silage.
were 11.83 and 10.99% for
unchopped and chopped silage, respectively.
Effect of growth period on dry matter percentage and
VFA are shown in table 16. There were no significant
differences between growth period in percentage dry matter
and VFA (table 16). Chopping decreased (P<.06) valeric acid
of silages and increased ( P<. 06) dry matter content and
tended to decrease prop ionic acid ( table 17). The results
indicate that 2 wk growth and chopping, increased the
production of lactic acid, and decreased the pH and
productio~ of acetic acid of Guinea-'A' silages.
Discussion
In these studies, the fermentation characteristics of
Guinea-'A' and NB-21 forages cut at different growth stages
with and without additives were different from temperate
forage silages. According to Carpintero et al. (1969), a pH
value of 4. 2 or below, butyric acid concentration of less
than .2% and ammonical-N content of less than 11~{ of the
total-N have been identified as characteristics of well
preserved silage. According to Langston et al. ( 19 58) as
cited in Catchpoole and Henzell (1971), lactic acid content
in well preserved silage can be between 3 and 13%, dry
60
TABLE 16. EFFECT OF GROWTH STAGE UPON DRY MATTER PERCENTAGE AND VOLATILE FATTY ACID
CONCENTRATION, LARGE SILO
Item
Dry matter,%
Volatile fatty acids, % a Acetic Propionic Isobutyric Butyric Isovaleric Valerie
aDry basis
Growth period, wk 2 3
17.58
2.64 4.61 0 3.70
.28
.76
17.96
4.43 2.95
.75 5.22
.36
.12
SE
.68
. 77 1. 71
.53 2.63
.32
.28
61
TABLE 17. EFFECT OF CHOPPING UPON DRY MATTER PERCENTAGE AND VOLATILE FATTY ACID CONCENTRATION, LARGE SILO
Item
%a Dry matter, •
Volatile fatty acids, %b Acetic Prop ionic Isobutyric Butyric Isovaleric Valerica
a Unchopped vs chopped (P < .06). b Dry basis
Un chopped
16.56
3·,29 5.26 0 6.59
.64
.88
Chopped
18.99
3. 77 2.29
.75 2.34 0 0
SE
.69
. 77 1. 72
.53 2.63
.32
.28
62
matter basis. However, in this study, pH value of silages
ranged from 4.8 to 5.9, lactic acid concentrations of .05 to
2.9%, acetic acid concentration of 2.64 to 5.99% and butyric
acid concentration of .31 to 6.59% were observed, except in
addition of cassava tuber meal. When cassava tuber meal was
added those values were 4. 2, 7. O~~' 3. 4% and . 007% for pH,
lactic acid, acetic acid and butyric acid, respectively. It
is noteworthy, that in silages with added cassava tuber
meal, fermentation of forages was mainly due to lactic acid,
as in most temperate forage silages. In all the other
treatments, fermentation of forages was mainly due to acetic
acid and (or) propionic acid but, not due to the lactic
acid. According to the standard values mentioned above, all
silages except that with the addition of cassava tuber meal
treatment would be classified as poor quality silages.
Several workers have shown that the fermentation
pathway of tropical forage silages was different from
temperate forage silages (Miller et al., 1966; Catchpoole,
1968; Catchpoole and Williams, 1969; Catchpoole and Henzell,
1971; Tosi, 1973; Aguilera, 1975; Xande, 1978). According
to these workers, the factors responsible for preservation
of tropical forage, silages are not
have concluded that this process is
production of high concentration of
known. However, they
not related with the
lactic acid. Several
workers have suggested that acetic acid rather than lactic
63
acid is the main preservative in tropical forage silages
(Catchpoole, 1968; Catchpoole and Williams, 1969; Catchpoole
and Henzell, 1971; Tosi, 1973; Aguilera, 1975; Xande, 1978).
Silages made in this study had more acetic than lactic
acid, except when cassava tuber meal was added. It appears
that conservation of silages was not due to lactic acid but
may have been due to acetic acid. Addition of cassava tuber
meal in the mixture followed the normal procedure for
temperate forage silages and produced lactic acid
fermentation. Several workers have shown that formic acid
could inhibit undesirable fermentation in silage made from
temperate grasses (McDonald, 1981). However, addition of 3%
formic acid had no significant effect, compared to control
silages.
64
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67
Vicente-Chandler, J., S. Silva and J. Figarella. 1959. The effect of nitrogen fertilization and frequency of cutting on the yield and composition of three tropical grasses. Agron. J. 51:202.
Vogt, H. 1966. The use of tapioca meal in poultry rations. World Poultry Sci. J. 22:113.
Xande, A. 1978. L'ensilage d'herb, une technique de conservation d l'herbe permettant de pallier au deficit alimentaire des ruminants durant la periode du careme. 1. Aspects theorique et pratique particulari te des fourrage. (Ensilage of grass, a conservation technique for obviating the food shortage of ruminants during the dry season. 1. Theoretical and practical aspects -particularities of tropical forages.) J. Nouvelles Agronomiques des Antilles et de la_Guyane 4(2):63 (Via Herbage Abstr. 51(2):62, 1981).
CHAPTER IV JOURNAL ARTICLE II
EFFECT OF STAGE OF GROWTH AND CHOPPING LENGTH ON DIGESTIBILITY AND PALATABILITY OF GUINEA-'A' GRASS
Experiments were
Summary
conducted to investigate the
digestibility and palatability of Guinea-'A' grass silage by
sheep. Two- and 3-wk growth of Guinea-'A' grass was
harvested and ensiled chopped or unchopped in 210 liter
metal drums. Animals averaging 20 kg initially were used,
and feces were collected by means of light harness and
canvas bag. Apparent digestibility of dry matter, crude
protein, neutral detergent fiber (NDF) and acid detergent
fiber (ADF) were higher (P<. 01) for 2-wk, compared to the
3-wk growth. Chopping the grass before ensiling increased
( P<. 01) the apparent digestibility of dry matter, crude
protein, NDF, ADF and hemicellulose by sheep. In the
palatability trial, no significant differences were observed
for dry matter intake by sheep due to growth stage.
However, chopping increased ( P<. 01) dry matter intake by
sheep by almost 17%. The effect of chopping on increasing
silage intake by sheep may be associated with the better
fermentation of the chopped forage.
(Key Words: Tropical Forage Silages, Guinea Grass, Chopping
Length, Digestibility, Feed Intake, Stage of Growth)
68
69
Introduction
Silage making is not a common practice among small
livestock farmers in tropical countries, however, on
government agricultural stations, silage has been made with
varying success and with varying capital outlay in towers,
clamps, pi ts and trenches. Several research workers have
reported the characteristic features of silage made from
tropical herbage plants (Miller et al., 1963; 1966;
Catchpoole, 1965; 1966; 1968; Catchpoole and Williams, 1969;
Catchpoole and Henzell, 1971; Tosi, 1973; Xande, 1978).
According to these workers, the factors responsible for
preservation of tropical silage is not known, however, they
have concluded that this process is not related with the
production of high concentration of lactic acid.
It is common knowledge that the digestibility of
forages decrease with the maturity in temperate as well as
tropical forage. It is also interesting to note that the
chopping increased the digestibility and voluntary feed
intake of temperate forage silages by sheep (Dulphy and
Demarquilly, 1973; Dulphy and Michalet, 1975; Thomas et al.,
1976; Deswysen et al. , 1978; Anderson, 1982). The
objectives of this study were to investigate the effect of
stage of growth and chopping length on digestibility and
palatability of Guinea-'A' grass silage by sheep.
70
Methods and Materials
A complete description of the forage and preparation of
the silages is presented in Chapter III.
Briefly, silages were prepared from Guinea-A forage cut
at two stages of growth. The forage contained approximately
17% dry matter at 2-wk growth stage and 20% at 3-wk growth
stage. At each growth stage, the forage was divided into
two portions. One portion was chopped and the other portion
was not chopped. The materials were firmly packed in 210
liter metal drums doubled lined with . 08 mm polyethylene
bags at the approximate rate of 85 to 105 kg/drum. The bags
were sealed with plastic coated wire and the drums were
stored upright in an open barn from harvest (May, 1983)
until the initiation of sheep feeding trials (September,
1983).
Digestibility Studies. Two trials were conducted with
sheep averaging 20 kg initially. The sheep were placed in
three blocks of four each, by weight. Sheep within each
block were allotted at random to the silages, with
restriction that no animals would receive the same silage in
both trials.
All sheep were treated for internal parasites. The
sheep were fed the silages and 55 g of mineral-vitamin
mixture per day. One half of the daily allowance was fed at
0600 and the other at 1800. Water was provided ad libitum.
71
Initially, unchopped 3-wk growth silage was fed to all the
animals.
Initially all sheep were fed 400 g dry matter per day.
The amount offered was adjusted due to refusals by some
animals. The amounts consumed were 458, 385, 452 and 409 g
dry matter for silage made from 2-wk chopped, 2-wk
unchopped, 3-wk chopped and 3-wk unchopped, re spec ti vely.
The experimental diets were gradually introduced during a
3-d transition period. Following the transition period, the
sheep were fed the experimental diets for a 7-d preliminary
period followed by a 7-d collection period during which
total feces were collected. The sheep were kept in
individual 1.22 x 1.07 m pens. Canvas bags held by
harnesses as described by Fontenot and Hopkins (1965) were
used to collect feces.
Beginning 2 d before the start until 2 d prior to the
end of the 7-d collection period, the silages were sampled
at each feeding. The silage samples were frozen daily in
doubled plastic bags and composited at the end of the trial.
Refusals and feces were collected twice daily and dried for
24 hr at 55 C in an Unitherm oven, and were composited daily
by animal in polyethylene bags. At the end of the
collection period, the feces from each animal were weighed,
mixed and subsampled. Silage samples were dried at 55 C for
24 hr for dry matter determination, allowed to air
72
equilibrate, then ground to pass a 1 mm screen. Kjeldahl
nitrogen was determined on feces, refusals and silage
samples (A.O.A.C., 1980). All samples were analyzed for dry
matter (DM), NDF (Van Soest and Wine, 1967), ADF (Van Soest,
1963), lignin and cellulose (Van Soest and Wine, 1968). All
animals were weighed before and after the trial.
Palatability Studies. In conjunction with the
digestibility trials, the palatability of the silages was
evaluated in two trials with sheep. The 12 crossbred
wethers used in the digestion trials, with an average weight
of 20 kg, were used in two palatability trials. The lambs
were blocked by weight and allotted at random to the same
diets and by the same procedure as for the digestion trial.
The sheep were housed in individual 1. 22 x 1. 07 m
stalls in a semi-enclosed barn. Water was provided ad-
libitum and lambs were fed 55 g of mineral mixture per day.
The sheep were provided with fresh feed every 12 h. The
trial consisted of a 7-d preliminary period followed by a
7-d measurement period. During the measurement period,
refusals were collected once daily, weighed, dried at 55 C
in an Unitherm oven for 24 hr and reweighed.
The sheep were weighed before the start and at the end
of each palatability trial. The average of the initial and
final weights was used to determine metabolic size (Wk;5 ) on
which dry matter intake was calculated.
73
Silages were sampled throughout the measurement period.
The samples were frozen in plastic bags after each feeding.
At the end of the trial, samples were composited by
treatment, thoroughly mixed and a subsample was taken for
dry matter determination.
Statistical Analysis. Statistical analyses were
performed using the analyses of variance by the general
linear model procedure described by SAS (1982). Comparisons
were made to test 2- vs 3-wk growth, unchopped vs chopped
forages and the interaction.
Results and Discussion
Digestibility. Table 18 presents the composition of
silages used in the sheep digestion and palatability trials.
Growth period did not significantly affect percentage dry
matter, crude protein or cell wall fractions. Chopping
length had no significant effect on the percentage d~y
matter, crude protein or cell wall fractions of the silages.
Apparent digestibility of DM, CP, NDF and ADF were
higher (P<. 01) for 2-wk growth stage than the 3-wk growth
stage (table 19). Although not significantly different,
values for digestibility of the cell wall fractions tended
to be lower for the 3 wk growth. It is generally accepted
that the digestibility of forages decreases with increased
maturity (Devendra, 1977). This lower digestibilities in
mature forages are associated with the lower leaf to stem
TABLE 18. COMPOSITION AND CELL WALL FRACTIONS OF SILAGE IN SHEEP METABOLISM AND PALATABILITY TRIALS
-Growth eeriodi wk
2 3 Item Unchopped Chopped Unchopped Choppped SE
Dry matter, % a 16.1 19.1 17.1 18.9 .97
Crude protein, %a,b 13.S 16.9 17.2 14.3 .83
Cell wall fractions, % b
Neutral detergent fiber C 57.6 63.1 57.8 60.9 1.18 -..J -"'
Acid detergent fiber 46.1 44.8 42.3 l.3. 7 1.61
Cellulose 35.6 35.S 34.4 32.9 l .L,3
Hemicellulose 11.6 18.3 15.6 17.2 2.14
Lignin 7.9 7.0 4.7 6.5 .85
~Growth period x chopping (P < .OS). Dry basis.
C Unchopped vs chopped (P < .OS).
TABLE 19. APPARENT DIGESTIBILITY OF CUINEA-'A' SILAGE BY SHEEP
Growth Eeriod 1 wk 2 3
Item Unchopped Chopped Unchopped Chopped SE
- - - - - - - - - - - - % -------a b Dry matter' 59.1 66.1 55.7 60.1 1.1
Crude proteina,b,c 61.0 67.4 47.8 69.1 1. 7
Cell wall fractions
Neutral detergent fibera,b 56.8 66.6 52.7 59.3 1.6
a b -..J
Acid detergent fiber' 60.0 66.4 53.9 58.7 1.2 VI
Cellulose 67.2 75.8 65.3 61.9 4.3
Hemicellulose b 42.1 67.3 48.6 57.7 4.4
Lignin 37.2 38.7 32.8 35.1 1.6 --a b 2-wk vs 3-wk (P < .01).
Unchopped vs chopped (P < .01). cGrowth period x chopping (P < • 01).
76
ratio and high fiber in those forages. Leaf to stem ratios
were 1.98 and 1.22 whereas plant heights were 72 cm and 86
cm for 2- and 3-wk growth Guinea grass, respectively.
Chopping increased ( P<. 01) the apparent digestibility
of dry matter, CP, NDF, ADF and hemicellulose by sheep
(table 19). Dulphy and Demarquilly (1973) have found a
negative correlation between increasing chop length and
fermentation quality in temperate grass silage. According
to their results, the main advantage of short chop length
would appear to lie in the possibility of more efficient
compaction of the ensiled material and the release of
fermentable substrates for fermentation by microorganisms.
They noted that while fermentation quality differed with
chopping length, there were no significant differences in
the digestibility coefficients of different length temperate
forage silages offered to sheep. In trials with steers and
cows Balch et al. (1955) and Murdock (1965) found that
chopping increased the digestibility of the temperate forage
silage. Thomas et al. (1976) found that the digestibility
was unchanged for chopped temperate forage silage, but
significantly reduced for minced silage by sheep. On the
contrary, Grant et al. (1974) reported that chopping
increased the apparent and true digestibilities of dry
matter of Napier grass during wet season in Philippines.
Devendra ( 1977) also reported that chopping increased the
77
digestibility of nutrients of Guinea grass compared to long
forage.
was
Interaction between growth
observed for apparent
stage and chopping length
digestibility of CP.
Digestibility of CP increased more at 3-wk than 2-wk growth
due to chopping forage.
Palatability. No significant differences were observed
for dry matter intake of silage by sheep due to the growth
stage (table 20). Chopping increased (P<.01) the dry matter
intake by sheep by almost 17% ( table 20). The effect of
chopping on increasing feed intake by sheep may be
associated with the better fermentation of the chopped
forage. It may also be possible that the effective
breakdown with long silage was delayed, thus, the mean
retention time in the reticule-rumen of the undigestible
fraction would be longer and cause a lower level of
voluntary feed intake. Several workers have reported that
chopping had a significant beneficial effect on feed intake
during the dry season (Grant et al., 1974; Devendra, 1977).
According to Devendra (1977) the higher intake of dry matter
in chopped Guinea-'A'
the diet, compared
grass was due to the physical form of
to unchopped forages. Moore (1964)
stated that the effects of grinding and pelleting on forage
utilization are due to increased rate of passage, decreased
digestibility, increased rate of intake, decreased
TABLE 20. DRY MATTER INTAKE OF SHEEP FED GUINEA-'A' SILAGE
Growth period, wk 2
Item Unchopped Chopped Unchopped
Grams per day a 425 513 410
G w.75 d a rams per kg per ay 44.9 51.6 42.9
a Unchopped vs chopped (P < .01).
3 Chopped
540
53.4
SE
24.3
2.2
....... CX>
79
rumination and change in some physiological conditions in
the rumen. In particular, they reported that processing
helps the breakdown of the structural components of the
grass so that the structural inhibition of intake is reduced
and the grass is more accessible to the digestive processes.
Between chopping and pelleting, chopping is probably the
more common, and maximum benefits appears to be associated
with this method.
The intake data obtained from the palatability trial
(table 20) support the well documented conclusion that short
chopping of forages improves the intake of silage by sheep
(Dulphy and Demarquilly, 1973; Dulphy and Michalet, 1975;
Thomas et al., 1976; Deswysen et al., 1978; Anderson, 1982).
Several workers have reported that this increased intake is
associated with an improvement in the fermentation
characteristics of short chopped silage (Murdoch et al.,
1955; Balch et al., 1955; Murdoch, 1965; Dulphy and
Demarquilly, 1973; Deswysen et al., 1978; Anderson, 1982).
However, no significant effect of stage of maturity on
intake of Guinea 'A' silage (table 20) was observed. This
seems surprising in view of the effect of stage of maturity
on the fermentation quality of silage. However, Anderson
( 1982) has shown that there was no significant effect of
stage of maturity on silage intake by sheep.
In conclusion, the results presented here indicate that
80
the stage of maturity of the forages significantly affect
the digestibility of silages but had no effect on the
voluntary feed intake. Furthermore, chopping the forages
before ensiling increased the digestibility as well as the
feed intake of silage by sheep. The data indicate that
stage of growth influences digestibility and particle size
of forages is a prime factor influencing intake and
digestibility in sheep.
81
Literature cited
Anderson, R. 1982. Effect of stage of maturity and chop length on the chemical composition and utilization of formic acid-treated ryegrass and formic acid silage by sheep. Grass and Forage Sci. 27:139.
A.O.A.C. 1980. Official Methods of Analysis (12th Ed.). Association of Official Analytical Chemists. Washington, D.C.
Balch, C. C., J. C. Murdoch and J. Turner. 1955. The effect of chopping and lacerating before ensiling on the digestibility of silage by cows and steers. J. of the Brit. Grassland Soc. 10:326.
Catchpoole, V. R. 1965. Laboratory ensilage of sphacelata (Nandi) and Chloris gayana (C.P.I. Australian J. Agr. Res. 16:391.
Setaria 16144).
Catchpoole, V. R. 1966. Laboratory ensilage of Setaria sphacelata (Nandi) with molasses. Australian J. Exp. Agr. Anim. Husb. 6:76.
Catchpoole, V. R. 1968. Effect rate of nitrogen fertilizer sphacilata. Australian J. 8:569.
of season, maturity and on ensilage of Setaria Exp. Agr. Anim. Husb.
Catchpoole, V. R. and E. F. Henzell. 1971. Silage and silage making from tropical herbage species. Herbage Abstr. 41:213.
Catchpoole, V. R. and N. T. Williams. 1969. pattern of silage fermentation in two grasses. J. Brit. Grassland Soc. 24:317.
The general subtropical
Deswysen, A., M. Vanbelle and M. Focant. 1978. The effect of silage chop length on the voluntary intake and rumination behaviour of sheep. J. Brit. Grassland Soc. 33:107.
82
Devendra, C. 1977. Studies in the intake and digestibility of two varieties (Serdang and Coloniao) of Guinea grass (Panicum maximum) by goats and sheep. Mardi Res. Bull. 5(2):110.
Dulphy, J. P. and C. Demarqui lly. 1973. Influence de la machine de recolte et de la finesse de hachage sur la valeur alimentaire des ensilage. (Influence of harvesting machine and chop length on the alimentary value of silage.) Ann. Zootechnie 22:199.
Dulphy, J. P. and B. Michalet. 1975. Influence comparee de la machine de recolte sur le quantities d'ensilage ingerees par de genisses et des moutons. (Comparative effect of harvesting machine on silage intake by heifers and sheep.) Ann. Zootechnie 24:757.
Fontenot, J. P. and H. A. Hopkins. physical form of different parts rations of feedlot performance and Anim. Sci. 24(1):62.
1965. Effect of of lamb fattening digestibility. J.
Grant, R. J., P. J. Vansoest, R. E. McDowell and C. B. Perez, Jr. 1974. Intake, digestibility and metabolic loss of Napier grass by cattle and buffaloes when fed wilted, chopped and whole. J. Anim. Sci. 39(2):423.
Miller, W. J., C. M. Clifton and N. W. Cameron. 1963. Ensiling characteristics of coastal Bermudagrass harvested at the pre-head and full-head stages of growth. J. Dairy Sci. 46:727.
Miller, W. J., Cameron. Sudangrass 49:477.
C. M. Clifton, P. R. Fowler and N. W. 1966. Ensiling characteristics of Tift and Coastal Bermudagrass. J. Dairy Sci.
Moore, J. A. 1964. Symposium on forage utilization: Nutritive value of forage as affected by physicalform. 1. General principles involved with ruminants and effect of feeding pelleted or wafered forage to dairy
83
cattle. J. Anim. Sci. 23:230.
Murdoch, J. C. 1965. The effect of length of silage on its voluntary intake by cattle. J. Brit. Grassland Soc. 20: 54.
Murdoch, J. C., D. A. Balch, M. C. Holdsworth and M. Wood. 1955. The effect of chopping, lacerating and wi 1 ting of herbage on the chamical composition of silage. J. Brit. Grassland Soc. 10:181.
SAS. 1982. SAS User's Guide. Statistical Analysis System Institute Inc., Cary, NC.
Thomas, P. C., N. C. Kelly and· M. K. Wait. effect of physical form of a silage on its consumption and digestibility by sheep. Grassland Soc. 31:19.
1976. The voluntary J. Brit.
Tosi, H. 1972. Efei to da adicao de ni vei s crescentes de melaco na ensilagem do capim elefante (Penniseturn purpureurn, Schum) variedade. Napier. M.S. Thesis. Estado de Sao Paulo - Brazil.
Van Soest, P. J. 1963. The use of analysis of fibrous feeds: I I. determination of fiber and lignin. Agr. Chern. 48:829.
detergents in the A rapid method for
J. Assoc. Official
Van Soest, P. J. and R. H. Wine. 1967. Use of detergents in the analysis of fibrous feeds. IV. The determination of plant cell wall constituents. J. Assoc. Official Anal. Chern. 50:50.
Van Soest, P. J. and R. H. Wine. 1968. Determination of lignin and cellulose in acid-detergent fiber with permanganate. J. Assoc. Official Anal. Chern. 51:780.
Xande, A. 1978. L'ensilage d'herb, une technique de conservation d l'herbe permettant de pallier au deficit alimentaire des ruminants durant la periode du carerne.
84
1. Aspects theorique et pratique - particularite des fourrage. (Ensilage of grass, a conservation technique for obviating the food shortage of ruminants during the dry season. 1. Theoretical and practical aspects -particularities of tropical forages.) J. Nouvelles Agronomiques des Antilles et de la Guyane 4(2):63 (Via Herbage Abstr. 51(2):62, 1981).
CHAPTER V EFFECT OF CUTTING FREQUENCY ON YIELD OF GUINEA-'A'
(PANICUM MAXIMUM) AND NB-21 (PENNISETUM PURPUREUM X PENNISETUM AMERICANUM)
FODDERS IN SRI LANKA
Summary
Research was undertaken in Sri Lanka to study the
effect of cutting frequency on yield of Guinea-'A' and NB-21
grasses. All plots were cut uniformly to a height of 12.5
cm from ground level prior to the commencement of the trial.
Plots were harvested l, 2 and 3 wk after new foliage emerged
and yields were recorded. Plots were arranged in a
randomized block design with three replications, harvested
twice more at 30-d intervals and regrowth measurements were
taken. Lengthening the cutting interval resulted in linear
increase ( P<. 01) in the dry matter yield of both grasses.
It was also shown that the regrowth of Guinea-'A' and NB-21
were affected by the length of period of the previous
growth.
(Key Words: Frequency of Cutting, Yield, Guinea Grass,
NB-21, Regrowth)
Introduction
The main objective of pasture management is to secure
the highest output of animal products per hectare.
Intensive management involves the production of high yields
of high quality forage per hectare, while maintaining the
integrity of the sward. Several factors control and
85
86
contribute to high production of pastures. Frequency of
defoliation is a primary factor which governs the yield and
quality of forages.
Stored reserves are important for regrowth of perennial
grasses. The storage organs may be roots, rhizomes or the
bases of the stems. Defoliation which results in new top
growth decreases the plant stored reserves. Excessive
defoliation can result in a drastic reduction of herbage
yields both during and after the cutting treatment due. to
carbohydrate starvation (Appadurai, 1968). On the other
hand, as soon as adequate leaf areas are reached
p~otosynthesis begins and storage of carbohydrates will
occur.
The objective of this study was to study the effect of
cutting frequency on yield of Guinea-'A' and NB-21 grasses.
Materials and Methods
Dry Matter Yield. Two fodder grasses namely Guinea-'A'
and NB-21, established in 1980, were grown at the Mawela
Farm, Peradeniya (Longitude 80° 29'E, latitude 7° 13'N,
elevation 485m), Sri Lanka in a reddish brown latasolic soil
with pH values of 5. 8 for the Guinea-' A' and 4. 9 for the
NB-21 areas. Plots measuring 17. 4 x 2. 8 rn for Guinea-' A'
and 10 x 8.2 rn for NB-21 were arranged in a randomized block
design with three replications. Phosphorous (P) as triple
super-phosphate and N as urea were applied at the rate of
87
112 and 168.5 kg/ha, respectively, uniformly to the entire
area at the beginning of the trial in May, 1983. Guinea-'A'
plots were irrigated during the trial. Each forage was
harvested at three stages of plant growth, corresponding to
l, 2 and 3 wk after cutting the foliage. The grasses were
cut uniformly to a height of 12.5 cm from ground level, at 1
wk intervals, prior to the commencement of the trial so that
all plots were harvested on the same day for ensiling.
At each harvesting the herbage was cut to 12.5 cm from
ground level, as at commencement, and the forages from the
three replicates were collected and weighed separately. The
sub-samples taken were dried in an Unitherm oven at 55 C for
24 h and used for the determination of dry matter. The
remaining fresh material was used for ensiling in small
silos (Chapter III).
All plots were harvested again twice, at 30-d
intervals, and yield measurements were taken. Effects of
the three cutting frequencies on plant growth were measured
by measuring the plant height, and determining leaf to stem
ratio.
Statistical Analysis. Statistical analyses were
performed using the analysis of variance by the general
linear model procedure described by SAS (1982). Comparisons
were made to test linear and quadratic effects of stage of
growth.
88
Results and Discussion
Dry matter yields of Guinea-'A' and NB-21 as affected
by frequency of cutting are presented in table 21.
Lengthening the cutting interval resulted in a linear
increase (P<.01) in dry matter yield of both grasses. Dry
matter yield of Guinea-' A' was increased almost two- and
three-fold with 2- and 3-wk, compared to the 1-wk cutting
interval. This increase in yield with less frequent cutting
is in ~eneral agreement with previous research (Watkins and
Lewy, 1951; Vicente-Chandler et al., 1959; Oyenuga, 1960;
Goonewardene and Appadurai, 1971; Mani and Kothandaraman,
1980; Sanghi and Raj, 1983).
Table 22 presents the dry matter yield of Guinea-' A'
and NB-21 after two consecutive 30-d regrowth periods. It
is important to note that the regrowth on all treatments
occurred during the same time period and the ref ore, under
the same environmental conditions. The dry matter yield of
Guinea-' A' for the first 30 d tended to increase with the
length of period of previous growth. Dry matter yield
during the second 30 d regrowth was linearly increased
(P<.01) with the length of the initial growth periods. Poor
dry matter yield in 1 wk cut fodder may be associated with
the less available leaf area for photosynthesis and less
carbohydrate reserves in roots and stems. Dry matter yield
89
TABLE 21, DRY MATTER YIELD OF GUINEA-'A' AND NB-21 AS AFFECTED BY LENGTH OF GROWTH PERIOD
Grass 1 Growth period, wk
2 3
-1 -1 ------- kg•ha •cut -------
Guinea-'A'a
NB-2la
760
137
aLinear effect (P < .01).
1892
214
2449
274
SE
136
9
90
TABLE 22. REGROWTH DRY MATTER YIELD OF GUINEA-'A' AND NB-21 AS AFFECTED BY GROWTH PERIOD
Days of Previous growth 2eriod, wk Grass regrowth 1 2 3 SE
-1 -1 ------ kg•ha •cut
Guinea-'A' First 30 d 1285 1330 1611 340 Second 30 da 1801 2358 2849 56
NB-21 First 30 da 150 212 352 18 Second 30 da 371 452 661 43
~inear effect (P < .01).
91
for regrowth of NB-21, for both 30 d periods were linearly
increased with length of the initial growth periods.
There was no significant effect of frequency of cutting
on the plant height or leaf to stem ratio of regrowth of
Guinea-'A' and NB-21 (tables 23 and 24).
TABLE 23. LEAF TO STEM RATIO AND PLANT HEIGHTS OF GUINEA-'A' AS AFFECTED IlY GROWTH PERIOD
Days of Previous growth ~eriod, wk Item regrowth 1 2 3
Leaf/stem First 30 d 5.98 8.07 4.00
Second 30 d 2.44 2.44 2.61 '° N
Plant height, cm First 30 d 78 77 71
Second 30 d 92 92 9J
TABLE 2/•. LEAF TO STEM RATIO AND PLANT HEIGHTS OF NB-21 AS AFFECTED BY GROWTH PERIOD
Days of Previous growth eeriod! wk Item regrowth 1 2 3
Leaf/stem First 30 d 8.05 4.85 5.05
Second 30 d 2.25 2.09 2.54 \0 \.,)
Plant height, cm First 30 d 77 79 76
Second 30 d 94 94 92
94
Literature Cited
Appadurai, R. R. 1968. Grassland Farming in Ceylon. T.B.S. Godamunne and Sons Ltd., Kandy, Ceylon.
Goonewardene, L. A. and R. R. Appadurai. 1971. Changes in feeding value with growth in three important fodder grasses of Ceylon. Trop. Agriculturist 127(3 and 4):145.
Mani, A. K. and G. V. Kothandaraman. 1980. Influence of nitrogen and stages of cutting on the yield of hybrid napier grass varieties. Madras Agric. J. 67(12):797.
Omaliko, C. P. E. 1980. Influence of initial ~utting date and cutting frequency on yield and quality of star, elephant and Guinea grasses. Grass and Forage Sci. 35:139.
Oyenuga, V. A. 1960. Effect of stage of growth and frequency of cutting on the yield and chemical composition of some Nigerian fodder grasses - Panicurn maximum Jacq. J. Agr. Sci. (Cambridge) 55:339.
Sanghi, A. K. and M. F. Raj. 1983. Performance and phenotypic stability in pearlmillet and Napier hybrids. Indian J. Agr. Sci. 53(2):105.
SAS. 1982. SAS User's Guide. Statistical Analysis System Analysis, Inc., Cary, NC.
Vicente-Chandler, J., S. Silva and J. Figarella. 1959. The effect of nitrogen fertilization and frequency of cutting on the yield and composition of three tropical grasses. Agron. J. 51:202.
Watkins, J. W. and M. Lewy-Van Severin. 1951. Effect of frequency and height of cutting on the yield,, stand and protein content of some forages in El Salvador. Agron. J. 43(6):291.
GENERAL DISCUSSION
The rapid increase in costs and the shortage of
concentrate feeds in recent years have highlighted the
importance of herbage as a cheap source of food for farm
animals in Sri Lanka. Traditionally, forage for livestock
of low quality and was provided by indigenous grasses
nutritive value. In view of the poor performance of animals
in these natural grazing lands, improved varieties have been
developed.
the years
These improved varieties have been tried over
and recommendations for different agro-climatic
zones have been made.
The rainfall in Sri Lanka is seasonal, and as a result,
excess amounts
seasons, which
unavailability
quantity is a
of forages are
are not properly
of good quality
general problem
available in the rainy
utilized. However, the
forage in the required
and in absence of any
conserved forage, this problem becomes more serious during
the drier months when there is little or no growth of the
forage. Therefore, forage conservation could be used as an
insurance against the scarcity of feed during the dry
season.
Forage could be conserved either as hay or silage,
however, none of these practices are commonly practiced in
Sri Lanka. There are various advantages in making silage
over making hay. Hay making is a problem in Sri Lanka,
95
96
because the periods of maximum forage production coincide
with the periods of frequent rains. The effect of rain on
cut herbage results in loss of soluble carbohydrates and
other nutrients, and loss of dry matter by microbial
decomposition. Prolonged wet weather results in complete
loss of the material. High relative humidity is also a
problem in hay making which will permit the drying of grass
only to a certain moisture content and this may be too high
for safe storage of grass as hay. Therefore, silage making
appears to be more feasible than making of hay.
Silage making is not a common practice among livestock
farmers in Sri Lanka, however, on government farms, silage
has been made with varying success and with varying capital
outlay in towers, pits and trenches. However, information
about their fermentation characteristics, feeding value and
utilization is insufficient and often incomplete. The
objectives of the present study were, therefore, to obtain
information on the fermentation characteristics and feeding
value of two fodder grasses grown in the mid-country of Sri
Lanka for ruminants at various stages of growth and ensiled
with different additives.
Two fodder grasses, Guinea-'A' and NB-21 were harvested
at 1, 2 and 3 wk of growth, chopped and ensi led alone or
with, cassava tuber meal, coconut oil meal or formic acid.
In another study, Guinea-' A' grass was hand-chopped into
97
1.5, 7.5 and 15 cm and ensiled in small laboratory silos to
study the effect of chopping length on the ensiling
characteristics of the forage. In a third study, Guinea-'A'
grass was harvested at 2 and 3 wk of growth ensiled chopped
or unchopped in metal drums. Fermentation characteristics
of the ensiled material were studied and digestibility and
palatability trials were conducted to study the feeding
value of silages by sheep.
According to the results, the factors responsible for
preservation of these forages is not related with the high
production of high concentrations of lactic acid, as in
temperate forage silages. According to Langston et al.
(1958) as cited in Catcpoole and Henzell (1971), lactic acid
content in well preserved silage can be between 3 and 13% of
dry basis. However, in this study, pH values of silages
ranged from 4.8 to 5.9, lactic acid concentration of .05 to
2.9%, acetic acid concentration of 2.64 to 5.99% and butyric
acid concentration of .31 to 6.59% was observed, except in
addition of cassava tuber meal. In silage with addition of
cassava tuber meal, those values were 4. 2, 7%, 3. 4% and
.007% for pH, lactic, acetic and butyric acid, respectively.
The data shows that the .fermentation of forages was not due
to lactic acid but may have been due to acetic acid and (or)
propionic acid. These data are in agreement with the
previous work done with tropical forage silages (Miller et
98
al, 1966; Catchpoole, 1968; Catchpoole and Williams, 1969;
1975; Catchpoole and Henzell,
Xande, 1978). However,
1971; Tosi, 1973; Aguilera,
i~ forages with addition of cassava
tuber meal, fermentation of forages was mainly due to lactic
acid as in most temperate for age silages. Addition of 3%
formic acid had no significant effect over control silage
and followed the same type of fermentation as in the
control.
Chopping the grass into fine pieces before ensiling
increased the lactic and
butyric acid production.
digestibility and intake
acetic acid and decreased the
Chopping also increased the
of Guinea-'A' grass silage by
sheep. This may
the
be associated with the more efficient
and the release of
fermentation by
compaction of
fermentable
ensiled material
substrates for rapid
microorganisms. This is in agreement with previous work
(Murdoch et al., 1955;
Dulphy and Demarquilly,
1977; Deswysen et al. ,
Balch et al., 1955; Murdoch, 1965;
1974; Grant et al., 1974; Devendra,
1978; Anderson, 1982). However,
there was no significant effect of stage of maturity on
intake of Guinea-'A' silage. This is in agreement with
Anderson (1982), who has shown that there was no significant
effect of stage of maturity on silage intake by sheep.
According to the dry matter yield study, cutting the
grass at 3 wk growth stage is better than 1 and 2 wk and
99
resulted in a higher regrowth of forages. This higher yield
of 3 wk growth was associated with medium quality forages.
The low yields of NB-21 as compared to Guinea-' A' may be
attributed to moisture stress as Guinea-' A' was irrigated
during periods of low rainfall, whereas NB-21 was not
irrigated. Also frequent cuttings would be expected to
depress yields of NB-21 more than Guinea-' A', the former
being a tall and erect species which would have fewer leaves
after cutting and would require a longer period for
regrowth.
In conclusion, the results presenced here indicate that
the criteria of preservation quality for temperate grasses
do not apply for tropical grasses, because of a different
fermentation pathway. The fermentation of forages may have
been due to acetic acid and (or) propionic acid. Addition
of cassava tuber meal and coconut oil meal improved the
quality of the silage compared to the control. However, the
control silages had good aroma and good fermentation.
Although the silages of the two grasses may not be compared,
because of being different experiments, it may be concluded
that NB-21 produced the better silage. The soluble
carbohydrate, crude protein and lactic acid for a given
additive was higher for NB-21 than for Guinea-' A' .
NB-21 also produced a silage with the better aroma.
of maturity of the silages significantly affect
The
Stage
the
100
digestibility of silage but had no effect on the voluntary
feed intake. Chopping the forages before ensiling increased
the digestibility as well as the feed intake of silage by
sheep, however, the values obtained for intake and
digestibility of unchopped silages were good. The data
indicate that the tropical forages could be ensiled even
without additives or chopping when cut at proper stage of
growth, and obtain quality silage. However, it should be
noted that it may not be feasible to harvest very early
growth stage forage for continuous productivity of the
forages.
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111
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APPENDIX
112
113
TAtL: 25. COMPOSITION OF THE MINERAL MIXTURE USED IN ANIMAL TRIALS (SUPER-MIX)
Item
Calcium Phosphorous Sodium chloride Vitamin/Trace element mixture Vitamin A, IU Vitamin D3 , IU Vitamin E, mg Magnesium, g Iron, g Zn, g
Manganese, g Copper, g Cobalt Iodine, g
Per kg Percent mixture
20.32 7.20
30.00 2.20
150,000 25,000
50 227
136.2 136.0 34.05 12.71
3.17 9.08
114
TABLE 26, EXA..'1PLE OF ANALYSIS OF VARIANCE,a SMALL SILO STUDY
Source Df
Model Error Corrected total
Model Growth stage Additive Growth stage x additive
Contrasts Linear growth stage Quadratic growth stage Control vs additives Fonnic acid vs cassava tuber
meal and coconut oil meal Cassava tuber meal vs coconut
oil meal
aGeneral linear model procedure.
11 60 71
2 3 6
1 1 1
1
1
115
TABLE 2 7. EXAMPLE OF ANALYSIS OF V ARIAi'JCE, a PALATABILITY TRIAL
Source Df
Model Error Corrected total
Model Trial Block Trial x block Growth stage Chopping Growth stage x chopping Trial x growth stage Trial x chopping Trial x growth stage x chopping Block x growth stage Block x chopping
aGeneral linear model procedure.
15 8
23
1 2 2 1 1 1 1 1 1 2 2
Item
TAHLE 28. FERMENTATION CHARACTERISTICS OF POST ENSILED MIXTURES (LARGE SILO)
Growth period, wk 2
Unchopped Chopped Unchopped 3
Chopped
- - % - - - - - - - - - -a b Water soluble carbohydrates '
Lactic acida,b
pH
~Dry basis. Growth period x chopping (P < .05).
3.15
.11
5.58
5.91
2.57
5.28
4.02
.07
5.7
4.07
.20
5.3
SE
.41
.08
.02
I-' I-'
°'
The vita has been removed from the scanned document
ENSILING CHARACTERISTICS, DIGESTIBILITY AND PALATABILITY
OF TROPICAL GRASSES AS AFFECTED BY GROWTH STAGE,
CHOPPING LENGTH AND ADDITIVES
Sujatha Panditharatne
(ABSTRACT}
Research was conducted in Sri Lanka to study the
effects of growth stage, chopping length and additives on
ensiling characteristics of Guinea-' A' (Panicum maximum -
Ecotype-'A') and NB-21 (Pennisetum purpureum Schumac x
Pennisetum americanum). The forages were harvested 1, 2 and
3 wk after growth, chopped and ensiled in small laboratory
silos (3 liter cardboard cylinders double lined with
polyethylene bags) alone or with additions of cassava tuber
meal, coconut oil meal and formic acid. Cutting grass at 1
wk increased (P<.05) acetic and lactic acid of silage,
compared to 3 wk. Addition of cassava tuber meal and
coconut oil meal increased (P<.05) lactic acid and decreased
(P<. 05) pH and acetic acid of silage, compared with the
control. The effects were greater for cassava tuber meal.
In a second study 3-wk growth of Guinea-' A' grass was
hand chopped to 1. 5, 7. 5 and 15 cm, and ensi led in small
laboratory silos. Lactic and acetic acid of silage
increased (P<.01), whereas dry matter loss and pH decreased
(P<.05) with fineness of chop. In a third study, 2 and 3 wk
growths of Guinea-' A' were harvested and ensi led in 210
l,i ter metal
chopped or
drums, double lined with
unchopped. Cutting grass
polyethylene bags,
at 2 wk decreased
(P<.05) pH and increased (P<.01) lactic acid, compared to 3
wk. Chopping decreased (P<.05) the pH and increased (P<.05)
lactic and acetic acid of silage.
Experiments were also conducted to study the
digestibility and palatability by sheep of Guinea-'A' silage
prepared in the third study. Apparent digestibility of dry
matter (DM), crude protein (CP), neutral detergent fiber
(NDF) and acid detergent fiber (ADF) were higher (P<.01) for
2 wk compared to 3-wk growth. Chopping the grass before
ensiling increased (P<.01) the apparent digestibility of DM,
CP, NDF, ADF and hemicellulose. No significant differences
were observed for DM intake by sheep due to the growth
stage, but chopping increased (P<.01) DM intake by 17%.
Lengthening the cutting interval of Guinea-'A' and
NB-21 resulted in linear increases (P<.01) in DM yield.
