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Utilization of leucaena as supplement for growing dwarf sheep and goats in the humid zone of west Africa
Small Ruminant Research, 5 ( 1991 ) 75-82
75
Elsevier Science Publishers B.V., Amsterdam
Utilization of leucaena as supplement for growing dwarf sheep and goats in the humid zone of west Africa J.O. A d e j u m o a a n d A.A. A d e m o s u n b aDepartmem of Agricultural Sciences, Obafemi Awolowo University, Adeyemi College of Education, Ondo, Nigeria bDepartment of Animal Science, Obafemi A wolowo University, Ile-lfe, Nigeria (Accepted 14 May 1991 )
ABSTRACT Adejumo, J.O. and Ademosun, A.A., 1991. Utilization of leucaena as supplement for growing dwarf sheep and goats. Small Rumin. Res., 4: 75-82. Confined West African Dwarf sheep and goats were offered chopped fresh Leucaena leucocephala cv. Cunningham (leucaena) leaves at levels of 0, 20, 40, 60 and 80% in a diet with chopped fresh Panicum maximum (guinea grass) over a period of 16 weeks to measure intake, apparent digestibility and growth. Leucaena forage depressed intake of feed by both species, and goats consumed less than sheep. Dry matter intake was 39.6, 35.1, 33.9, 33.7 and 27.0 g/kg °-75 for goats on 0, 20, 40, 60 and 80% leucaena diets, respectively. The corresponding values for sheep up to the 60% diet were 69.3, 67.3, 64.8 and 58.4 g/kg °75. At six weeks, the health of sheep on the 80% leucaena diet deteriorated seriously and they were removed from the treatment. The overall growth rate improved by up to 40% for sheep (59.3 g/day) on addition of leucaena to the diet and 60% for goats (33.1 g/day). Sheep grew faster than goats (53.4 vs. 28.4 g/day). Dry matter (DM) digestibility of the diet rose with increasing level of leucaena and goats digested DM more extensively than sheep (61.8 vs. 56.1%). Digestibility of other feed components followed the same pattern as that of DM. It is suggested that to promote growth without adverse effects, leucaena should not comprise more than 40% and 60% of the diets of West African Dwarf sheep and goats, respectively, or less than 1.0 g mimosine/kg °75.
INTRODUCTION
Livestock production in the humid zone of West Africa is limited to species and breeds which can tolerate trypanosomiasis. As such, dwarf sheep and goats estimated to number 11 million, are the most abundant domestic ruminant species. These small animals have definite advantages over other species in that they are adapted to the environment in the humid zone; they continue to make sub,;tantial contributions to meat consumption; they are cheaper to rear than cattle; they require less space and shelter than cattle; and their meat can 0921-4488/91/$03.50
© 1991 - - Elsevier Science Publishers B.V.
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J.O. ADEJUMO AND A.A. ADEMOSUN
be handled easily by small families and communities in the absence of refrigeration (Ademosun, et al., 1984). One of the major factors limiting increased meat production from these animals is deficiency of good quality feed. The adapted grasses are known to have a high rate of growth under favourable conditions, resulting in high DM production but of low forage quality. In addition, the recurring dry seasons inhibit the growth of shallow-rooted grasses and legumes. This can, however, be overcome by supplementing the basal diet with locally available leguminous browse. Leucaena leucocephala (leucaena) has been shown to have great potential as a source of high quality feed for ruminants. It is fast growing when established and, apparently because of its deep roots, tolerates adverse moisture conditions and grows actively in the dry season. Leucaena is very rich in protein (leaves contain 25-30% crude protein) and minerals such as phosphorus, potassium, magnesium, calcium and trace elements as well as in vitamin A (Keogham, 1980). However, leucaena forage contains a toxic amino acid, mimosine, and may not be expected to serve as the entire diet of any animal, although there are indications that certain breeds of animals are capable of ingesting greater amounts (100%) of leucaena than others (Jones, 1980). The objective of this study was to determine the level at which leucaena can be fed to West African Dwarf sheep and goats to promote growth without adverse effects. MATERIALS AND METHODS
Forages and their preparation An approximately 1 ha plot of Leucaena leucocephala cv. Cunningham (leucaena) and Panicum maximum (guinea grass) was established at the International Institute of Tropical Agriculture (IITA) research farm at Ibadan. The plot was divided into 42 subplots and these were cut back over a period of 42 days at the rate of one sub-plot per day. The division of the plot into 42 ensured that a six-week-old regrowth of leucaena and guinea grass was used in the feeding trials. Leucaena and guinea grass were cut at the height of 100 and 30 cm from the ground, respectively. Previous experience has shown that optimum DM yield and nutritive value would be obtained for these forages at these cutting intervals and heights (Adejumo and Ademosun, 1985 ). The leaves (leaf plus stalk) ofleucaena were separated from stems. Leucaena leaves and guinea grass forage were put through a forage chopper set at 2 cm to minimize feed wastage and selectivity.
Description of animals Twenty West African Dwarf (WAD) sheep (rams) and twenty WAD goats (bucks) were used in the feeding trials. Weights averaged 16.18 + 0.08 kg for
77
LEUCAENA SUPPLEMENT FOR GROWING WAD GOATS TABLE 1 Composition of diets used in feeding and digestion trials with sheep and goats (g/100 g DM ) Leucaena level (%)
Crude protein
Acid detergent fiber
Cell-wall constituents
Cellulose
0 20 40 60 80
10.8 13.9 18.1 22.7 26.3
43.6 38.4 32.0 24.9 20.1
76.4 72.1 69.2 66.5 63.6
31.4 26.3 21.9 18.4 12.9
sheep and 7.00 +_0.32 kg for goats. The animals were treated for internal and external parasites prior to the trials and were individually housed. After 1 week of adaptation to the experimental conditions, the animals were divided into 5 groups, each of 4 sheep and 4 goats. The groups were randomly allotted to five diets in which 0, 20, 40, 60 and 80% of the fresh weight was provided by leucaena forage. Composition of these diets appears in Table 1. The experimental design was a randomized complete block design with four replications. The rations were offered ad libitum for 16 weeks, and records of individual voluntary intake and individual body weight changes were kept on a daily and bi-weekly basis, respectively. At six weeks, the health of sheep on the 80% leucaena diet deteriorated seriously due to mimosine toxicity and they were removed from the treatment. After the initial feeding study, three animals per species per treatment were maintained in digestion stalls for 21 days; adjustment 14 days and collection 7 days. The feed offered was restricted to 90% of the daily voluntary intake. The forages were fed at 0800 hr. Water and salt lick were available all the time. During the collection period, samples of each diet were taken daily. 10% aliquots o'f faeces were also collected daily and frozen for subsequent analyses.
Analyticalprocedures DM in :forage and faeces was obtained by oven drying at 100 °C for 24 hrs. For chemical analyses, samples were dried at 60 ° C and ground ( 1 mm mesh). Crude protein (CP) of feeds and faeces was determined by standard Kjeldahl procedure. Acid detergent fibre (ADF), cell wall constituents (CWC) and cellulose were measured by the methods of Goering and Van Soest (1970). Mimosine concentration (4% o f D M ) i n leucaena leaves (Jones, 1979)was used to estimate mimosine intake by the animals. The nutritive value index (NVI) was calculated as DM digestibility ( D M D ) multiplied by relative intake (Crampton et al., 1960).
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J.O. ADEJUMO AND A.A. ADEMOSUN
Statistical procedure Data were analysed by analysis of variance. Duncan's new multiple range test was used to test significant differences among means (Steel and Torrie, 1960). RESULTS
Composition of the diets varied from a low of 10.8% CP and a high of 43.6% ADF, 76.4% CWC and 31.4% cellulose for sole guinea grass (test diet) to a high of 26.3% CP and a low of 20.1% ADF, 63.6% CWC and 12.9% cellulose for 80% leucaena diet (Table 1 ). Dry matter intake (DMI) was affected by leucaena feeding ( P < 0.05 ) of both animal species (Table 2). DMI declined while the estimated mimosine intake rose with the level of leucaena in the diet. Over the 16 weeks of the feeding trials, the DMI was 65.0 g/kg °-75 for sheep and 33.9 g/kg °75 per day for goats. The NVI of the feed for sheep (45.9) on the 40% diet or for goats (29.0) on the 60% diet was higher ( P < 0.05 ) than on the other treatments. Mean NVI for sheep (44.1) was 1.7 times as great as for goats (25.8). Table 3 displays digestibility of DM, CP, ADF, CWC and cellulose by sheep and goats. In general, leucaena-mixed diets were more digestible ( P < 0.05 ) than controls, digestibility rose with increasing levels of leucaena, and this was indicated with all nutrients. Goats digested all feed components more extensively than did sheep. Mean apparent digestibilities of DM, CP, ADF, CWC and cellulose by goats were 61.8, 73.9, 59.7, 64.2 and 66.3% for 0, 20, 40, 60 and 80% leucaena diets. The corresponding digestibility values for sheep were 56.1, 71.4, 56.8, 41.4 and 64.8%. TABLE2 Dry matter intake ( D M I ) by sheep and goats and nutritive value index ( N V I ) o f guinea grass with different levels o f leucaena Item
Species
Leucaena level, % 0
D M I , g / k g 0"75
DMI, % o f body weight Mimosine intake, g / k g °75 NVI
Sheep Goats Sheep Goats Sheep Goats Sheep Goats
20
69.26 a 67.34 ab 39.,58 a 35.14 b 3.21 a 3.17 a 2.21 a 1.96 b 0.00 0.54 0.00 0.28 43.28 b 43.86 b 25.12 b 25.61 b
Mean _+SD 2 40
60
80
64.83 b 33.88 b 3.01 a 1.89 b 1.03 0.54 45.86 ~ 25.79 b
58.39 c 33.70 b 2.67 b 1.88 b 1.40 0.80 43.43 b 29.02 ~
DN ~ 27.04 c ND ~ 1.51 c ND ~ 0.87 ND l 23.51 c
"~Means in the same row not followed by the same letter are different ( P < 0.05). Not determined. 2Standard deviation.
64.96+4.74 33.87 + 4.50 3.02 + 0.25 1.89+0.25 0.74+0.61 0.50+0.36 44.11+1.19 25.81+2.01
LEUCAENA SUPPLEMENT FOR GROWING WAD GOATS
79
TABLE 3 Digestibility coefficients (%) o f guinea grass with different levels o f leucaena fed to sheep and goats Feed c o m p o n e n t s
Dry matter Crude protein ADF 2 CWC 3 Cellulose
Species
Sheep Goats Sheep Goats Sheep Goats Sheep Goats Sheep Goats
Leucaena levels, %
Mean + SD ~
0
20
40
60
80
50.0 a 50.8 ¢ 66.4 c 68.9 c 52.6 b 56.6 b 55.4 a 58.1 ~ 58.8 b 61.7 b
52.1 a 58.3 b 67.3 ¢ 69.5 c 52.4 b 55.7 b 55.6 d 59.8 ¢ 62.0 ¢ 64.9 b
56.6 c 60.9 b 71.6 b 74.7 b 52.9 b 55.8 b 59.6 ~ 61.6 ~ 62.4 ¢ 65.6 b
59,5 b 68.9 a 75.4 a 77.9" 61.5 a 63.9" 64.8 b 67.7 b
62.5 a 70.3 ~ 76.5 ~ 78.6" 64.5 ~ 66.7 a 71.6 ~ 73.7" 72.8 ~ 73.5"
68.1 b
65.6 b
56.1 _+5.2 61.8_+8.0 71.4_+4.6 73.9 + 4.6 56.8_+5.8 59.7_+ 5.2 61.4_+6.9 64.2_+6.4 64.8 _+5.6 66.3+_4.4
a~aMeans in the same row, not followed by the same letter, are different ( P < 0.05 ). Standard deviation. 2Acid detergent fiber 3Cell-wall constituents. TABLE 4 G r o w t h rate of sheep and goats fed guinea grass with different levels of leucaena Item
Starting weight, kg G r o w t h rates, g / d a y Week 1-8 Week 9-16 Overall
Species
Mean + SD 2
Leucaena levels, % 0
20
40
60
80
Sheep Goats
16.20 7.25
16.10 6.98
16.20 7.10
16.30 7.20
16.10 6.45
16.18+0108 7.00+0.32
Sheep Goats Sheep Goats Sheep Goats
58.41 ¢ 29.43 c 39.43 b 19.29 a 48.92 ¢ 24.36 c
65.15 b 36.31 b 41.71 b 20.93 a 53.43 b 28.62 b
73.18 a 38.10 b 45.46 a 23.42 a 59.32 a 30.76 b
73.45 a 42.50 a 32.27 c 23.76 a 51.86 b 33.13"
ND I 45.20 a ND t 5.44 b ND I 25.32 c
67.55+7.21 38.31 + 6.08 39.72+5.55 18.57+7.57 53.38+4.38 28.44 + 3.67
"bCMeans in the same row not followed by the same letter are different ( P < 0.05 ). Not determined. 2Standard deviation.
During weeks 1-8, growth rate of sheep on 60% (73.4 g/day) and of goats on 80% (45.2 g/day) diet was the highest (P<0.05; Table 4). At 10 weeks of feeding, ~,~heepon 60% and goats on 80% leucaena started to show symptoms of leucaena toxicity which included loss of hair and excessive salivation. Growth rates of both species during weeks 9-16 were lower than in the first period; s]aeep on 60% and goats on 80% leucaena had the lowest growth rates. The overaU growth rate improved ( P < 0.05 ) by addition of leucaena to the
80
J.O. ADEJUMO AND A.A. ADEMOSUN
diets up to the 40% level for sheep and 60% for goats. Sheep grew faster than goats (53.4 vs. 28.4 g/day). DISCUSSION
Based on conventional measures of quality such as CP and ADF, the quality of the diet improved by the addition of leucaena (Table 1 ). Observations in many parts of the world have shown leucaena to be a valuable protein supplement (Jones, 1979; Aii and Stobbs, 1980). DMI increased as the percentage of leucaena in the diet was increased (Table 2 ) in conformity with previous findings with this legume (Jones et al., 1978). They reported low voluntary iniake with cattle ( 1.8 to 2.7% of body weight or 58 to 85 g/kg °'75) when fed a pure leucaena diet. In the present study the most marked depression in intake by sheep and goats occurred when the diet contained more than 40% and 60% of leucaena, respectively. Goats consumed less DM and digested it more completely than did sheep. This is similar to the findings of Huston et al. (1986) who observed that goats consumed 53% less DM, and showed a 9% greater organic matter digestibility compared with sheep. These figures were attributable to the differences in consumption capacity of DM and in retention time, goats having a relatively small reticulorumen and probably a longer retention time. Since the extent of digestion is the net result of rates of digestion and passage (Mertens, 1977), digestibility was greater in goats. DMD values for both sheep and goats increased with increasing level of leucaena in the diets (Table 3 ). The lower DMD value of guinea grass may be due to the fact that stems were included in the test diet. Stem is less digestible as a result of its high degree of cell-wall lignification (Ademosun, 1973 ). High DMD of the high level leucaena diet may be explained in terms of low intake associated with increasing level of leucaena in the diet (Table 2) and extended retention time in the reticulorumen. The longer the retention time the greater is the microbial fermentation of cellulose and hemicellulose which cannot be digested in the small intestine with the animals' own enzymes. The higher digestibilities of all other components of the diets with high leucaena levels (Table 3 ) are a reflection of the high DMD. Rate of growth improved with addition of leucaena to the diet and was highest for sheep on 40% and for goats on 60% leucaena, but decreased thereafter (Table 4 ). Previous investigations have shown that animals on high level (more than 60%) leucaena either maintain weight, lose weight throughout the experimental period or gain weight to begin with and lose weight subsequently (Jones et al., 1978). The low DMI, loss of hair, excessive salivation and reduced weight gain of animals on the high level leucaena diet are thought to be due to chronic mimosine toxicity resulting from prolonged intake ofleucaena (Reis et al., 1975;
LEUCAENA SUPPLEMENT FOR GROWING WAD GOATS
81
Hegarty et al., 1976). Goats tolerated high levels of leucaena (60%) better than sheep and this may be attributable to lower DMI in goats compared with sheep (Table 2) which thus resulted in lower intake of mimosine (0.80 vs. 1.40 g / k g °75). The nutritive value o f a forage is a function o f the daily intake of digestible D M and therefore depends on the quantity o f feed eaten and the digestibility of the feed. The high D M D o f high leucaena diets markedly influenced the NVI (Table 2 ), with the result that the overall nutritive value was higher for 40% leucaena which had the highest DMI. On the other hand, the difference in intake between sheep (65.0 g/kg °75 ) and goats (3 3.9 g/kg °75 ) in this study was high enough to more than offset a lower digestibility by sheep. Growth rate data (Table 4) followed closely those for NVI (Table 2 ), which had higher values for sheep than for goats. It is suggested that for better growth, WAD sheep and goats m a y not be fed diets containing more than 40% and 60% leucaena, respectively or less than 1.0 g mimosine per (kg body weight)O-75. ACKNOWLEDGEMENTS
The International Livestock Centre for Africa funded the project. Thanks are due to the International Institute for Tropical Agriculture, Ibadan, Nigeria, for providing research facilities.
REFERENCES Adejumo, J.O. and Ademosun, A.A., 1985. Effects of planting distance, cutting frequency and height on dry matter yield and nutritive value of Leucaena leucocephala sown alone and in mixture with Panicum maximum. J. Anim. Prod. Res., 6:209-221. Ademosun, A.A., 1973. Nutritive evaluation of Nigerian forages. IV. The effect of stage of maturity on the nutritive value of Panicum maximum. Niger. Agric. J., 10:170-177. Ademosun, A., Jansen, H.J. and Van Houtert, V., 1984. Goat management research at the University of Ife. In: Workshops on small ruminant production systems in the humid zone of West Africa, Ibadan, Intern. LivestockCentre for Africa, pp. 34-37. Aii, T. and Stobbs, T.H., 1980. Solubilityof the protein of tropical pasture species, and the rate of its digestion in the rumen. Anim. Fed. Sci. Technol., 5:183-192. Crampton, R.W., Donefer, E. and Lloyd, L.E., 1960. A nutritive value index for forages. J. Anita. Sci., 19: 538-544. Goering, H.R. and Van Soest, P.J., 1970. Foragefibre analyses (apparatus, reagents, procedures and some applications). Ag. Handbk. No. 379, WashingtonDC., USA. Hegarty, M.P., Court, R.D., Christie, M.D. and Lee, C.P., 1976. Mimosine in Leucaena leucocephala is metabolished to a goitrogen in ruminants. Aust. Vet. J., 52: 490-494. Huston, J.E., Rector, R.S., Ellis, W.C. and Allen, M.L., 1986. Dynamics of digestion in cattle, sheep, goats and deer. J. Anim. Sci., 62: 208. Jones, R.J., 1979. The value of Leucaena leucocephala as a feed for ruminants in the tropics. Wld. Anim. Rev., 31: 13-23.
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Jones, R.J., 1980. Toxicity studies with Leucaena in Hawaii. In: Tropical Crops and Pastures, Division of CSIRO, Australia. Divisional Report, 1979-1980, pp. 101. Jones, R.J., Blunt, C.C. and Nurnberg, B.T., 1978. Toxicity ofLeucaena leucocephala: the effect of iodine and mineral supplements on penned steers fed a sole diet ofleucaena. Aust. Vet. J., 54: 387-392. Keogham, J.M., 1980. Adaptable and productive forage legumes and grasses for more intensive small ruminant livestock systems in the Caribbean. Trop. Anim. Prod., 5: 8-14. Mertens, D.R., 1977. Dietary fiber components: relationship to rate and extent of ruminal digestion. Fed. Proc., 36:187. Reis, P.J., Tunks, D.A. and Hegarty, M.P., 1975. Fate of mimosine administered orally to sheep and its effectiveness as a defleecing agent. Aust. J. Biol. Sci., 28: 495-501. Steel, R.G.D. and Tome, J.H., 1960. Principles and Procedures of Statistics. McGraw-Hill Book Co. New York, U.S.A.
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Elsevier Science Publishers B.V., Amsterdam
Utilization of leucaena as supplement for growing dwarf sheep and goats in the humid zone of west Africa J.O. A d e j u m o a a n d A.A. A d e m o s u n b aDepartmem of Agricultural Sciences, Obafemi Awolowo University, Adeyemi College of Education, Ondo, Nigeria bDepartment of Animal Science, Obafemi A wolowo University, Ile-lfe, Nigeria (Accepted 14 May 1991 )
ABSTRACT Adejumo, J.O. and Ademosun, A.A., 1991. Utilization of leucaena as supplement for growing dwarf sheep and goats. Small Rumin. Res., 4: 75-82. Confined West African Dwarf sheep and goats were offered chopped fresh Leucaena leucocephala cv. Cunningham (leucaena) leaves at levels of 0, 20, 40, 60 and 80% in a diet with chopped fresh Panicum maximum (guinea grass) over a period of 16 weeks to measure intake, apparent digestibility and growth. Leucaena forage depressed intake of feed by both species, and goats consumed less than sheep. Dry matter intake was 39.6, 35.1, 33.9, 33.7 and 27.0 g/kg °-75 for goats on 0, 20, 40, 60 and 80% leucaena diets, respectively. The corresponding values for sheep up to the 60% diet were 69.3, 67.3, 64.8 and 58.4 g/kg °75. At six weeks, the health of sheep on the 80% leucaena diet deteriorated seriously and they were removed from the treatment. The overall growth rate improved by up to 40% for sheep (59.3 g/day) on addition of leucaena to the diet and 60% for goats (33.1 g/day). Sheep grew faster than goats (53.4 vs. 28.4 g/day). Dry matter (DM) digestibility of the diet rose with increasing level of leucaena and goats digested DM more extensively than sheep (61.8 vs. 56.1%). Digestibility of other feed components followed the same pattern as that of DM. It is suggested that to promote growth without adverse effects, leucaena should not comprise more than 40% and 60% of the diets of West African Dwarf sheep and goats, respectively, or less than 1.0 g mimosine/kg °75.
INTRODUCTION
Livestock production in the humid zone of West Africa is limited to species and breeds which can tolerate trypanosomiasis. As such, dwarf sheep and goats estimated to number 11 million, are the most abundant domestic ruminant species. These small animals have definite advantages over other species in that they are adapted to the environment in the humid zone; they continue to make sub,;tantial contributions to meat consumption; they are cheaper to rear than cattle; they require less space and shelter than cattle; and their meat can 0921-4488/91/$03.50
© 1991 - - Elsevier Science Publishers B.V.
76
J.O. ADEJUMO AND A.A. ADEMOSUN
be handled easily by small families and communities in the absence of refrigeration (Ademosun, et al., 1984). One of the major factors limiting increased meat production from these animals is deficiency of good quality feed. The adapted grasses are known to have a high rate of growth under favourable conditions, resulting in high DM production but of low forage quality. In addition, the recurring dry seasons inhibit the growth of shallow-rooted grasses and legumes. This can, however, be overcome by supplementing the basal diet with locally available leguminous browse. Leucaena leucocephala (leucaena) has been shown to have great potential as a source of high quality feed for ruminants. It is fast growing when established and, apparently because of its deep roots, tolerates adverse moisture conditions and grows actively in the dry season. Leucaena is very rich in protein (leaves contain 25-30% crude protein) and minerals such as phosphorus, potassium, magnesium, calcium and trace elements as well as in vitamin A (Keogham, 1980). However, leucaena forage contains a toxic amino acid, mimosine, and may not be expected to serve as the entire diet of any animal, although there are indications that certain breeds of animals are capable of ingesting greater amounts (100%) of leucaena than others (Jones, 1980). The objective of this study was to determine the level at which leucaena can be fed to West African Dwarf sheep and goats to promote growth without adverse effects. MATERIALS AND METHODS
Forages and their preparation An approximately 1 ha plot of Leucaena leucocephala cv. Cunningham (leucaena) and Panicum maximum (guinea grass) was established at the International Institute of Tropical Agriculture (IITA) research farm at Ibadan. The plot was divided into 42 subplots and these were cut back over a period of 42 days at the rate of one sub-plot per day. The division of the plot into 42 ensured that a six-week-old regrowth of leucaena and guinea grass was used in the feeding trials. Leucaena and guinea grass were cut at the height of 100 and 30 cm from the ground, respectively. Previous experience has shown that optimum DM yield and nutritive value would be obtained for these forages at these cutting intervals and heights (Adejumo and Ademosun, 1985 ). The leaves (leaf plus stalk) ofleucaena were separated from stems. Leucaena leaves and guinea grass forage were put through a forage chopper set at 2 cm to minimize feed wastage and selectivity.
Description of animals Twenty West African Dwarf (WAD) sheep (rams) and twenty WAD goats (bucks) were used in the feeding trials. Weights averaged 16.18 + 0.08 kg for
77
LEUCAENA SUPPLEMENT FOR GROWING WAD GOATS TABLE 1 Composition of diets used in feeding and digestion trials with sheep and goats (g/100 g DM ) Leucaena level (%)
Crude protein
Acid detergent fiber
Cell-wall constituents
Cellulose
0 20 40 60 80
10.8 13.9 18.1 22.7 26.3
43.6 38.4 32.0 24.9 20.1
76.4 72.1 69.2 66.5 63.6
31.4 26.3 21.9 18.4 12.9
sheep and 7.00 +_0.32 kg for goats. The animals were treated for internal and external parasites prior to the trials and were individually housed. After 1 week of adaptation to the experimental conditions, the animals were divided into 5 groups, each of 4 sheep and 4 goats. The groups were randomly allotted to five diets in which 0, 20, 40, 60 and 80% of the fresh weight was provided by leucaena forage. Composition of these diets appears in Table 1. The experimental design was a randomized complete block design with four replications. The rations were offered ad libitum for 16 weeks, and records of individual voluntary intake and individual body weight changes were kept on a daily and bi-weekly basis, respectively. At six weeks, the health of sheep on the 80% leucaena diet deteriorated seriously due to mimosine toxicity and they were removed from the treatment. After the initial feeding study, three animals per species per treatment were maintained in digestion stalls for 21 days; adjustment 14 days and collection 7 days. The feed offered was restricted to 90% of the daily voluntary intake. The forages were fed at 0800 hr. Water and salt lick were available all the time. During the collection period, samples of each diet were taken daily. 10% aliquots o'f faeces were also collected daily and frozen for subsequent analyses.
Analyticalprocedures DM in :forage and faeces was obtained by oven drying at 100 °C for 24 hrs. For chemical analyses, samples were dried at 60 ° C and ground ( 1 mm mesh). Crude protein (CP) of feeds and faeces was determined by standard Kjeldahl procedure. Acid detergent fibre (ADF), cell wall constituents (CWC) and cellulose were measured by the methods of Goering and Van Soest (1970). Mimosine concentration (4% o f D M ) i n leucaena leaves (Jones, 1979)was used to estimate mimosine intake by the animals. The nutritive value index (NVI) was calculated as DM digestibility ( D M D ) multiplied by relative intake (Crampton et al., 1960).
78
J.O. ADEJUMO AND A.A. ADEMOSUN
Statistical procedure Data were analysed by analysis of variance. Duncan's new multiple range test was used to test significant differences among means (Steel and Torrie, 1960). RESULTS
Composition of the diets varied from a low of 10.8% CP and a high of 43.6% ADF, 76.4% CWC and 31.4% cellulose for sole guinea grass (test diet) to a high of 26.3% CP and a low of 20.1% ADF, 63.6% CWC and 12.9% cellulose for 80% leucaena diet (Table 1 ). Dry matter intake (DMI) was affected by leucaena feeding ( P < 0.05 ) of both animal species (Table 2). DMI declined while the estimated mimosine intake rose with the level of leucaena in the diet. Over the 16 weeks of the feeding trials, the DMI was 65.0 g/kg °-75 for sheep and 33.9 g/kg °75 per day for goats. The NVI of the feed for sheep (45.9) on the 40% diet or for goats (29.0) on the 60% diet was higher ( P < 0.05 ) than on the other treatments. Mean NVI for sheep (44.1) was 1.7 times as great as for goats (25.8). Table 3 displays digestibility of DM, CP, ADF, CWC and cellulose by sheep and goats. In general, leucaena-mixed diets were more digestible ( P < 0.05 ) than controls, digestibility rose with increasing levels of leucaena, and this was indicated with all nutrients. Goats digested all feed components more extensively than did sheep. Mean apparent digestibilities of DM, CP, ADF, CWC and cellulose by goats were 61.8, 73.9, 59.7, 64.2 and 66.3% for 0, 20, 40, 60 and 80% leucaena diets. The corresponding digestibility values for sheep were 56.1, 71.4, 56.8, 41.4 and 64.8%. TABLE2 Dry matter intake ( D M I ) by sheep and goats and nutritive value index ( N V I ) o f guinea grass with different levels o f leucaena Item
Species
Leucaena level, % 0
D M I , g / k g 0"75
DMI, % o f body weight Mimosine intake, g / k g °75 NVI
Sheep Goats Sheep Goats Sheep Goats Sheep Goats
20
69.26 a 67.34 ab 39.,58 a 35.14 b 3.21 a 3.17 a 2.21 a 1.96 b 0.00 0.54 0.00 0.28 43.28 b 43.86 b 25.12 b 25.61 b
Mean _+SD 2 40
60
80
64.83 b 33.88 b 3.01 a 1.89 b 1.03 0.54 45.86 ~ 25.79 b
58.39 c 33.70 b 2.67 b 1.88 b 1.40 0.80 43.43 b 29.02 ~
DN ~ 27.04 c ND ~ 1.51 c ND ~ 0.87 ND l 23.51 c
"~Means in the same row not followed by the same letter are different ( P < 0.05). Not determined. 2Standard deviation.
64.96+4.74 33.87 + 4.50 3.02 + 0.25 1.89+0.25 0.74+0.61 0.50+0.36 44.11+1.19 25.81+2.01
LEUCAENA SUPPLEMENT FOR GROWING WAD GOATS
79
TABLE 3 Digestibility coefficients (%) o f guinea grass with different levels o f leucaena fed to sheep and goats Feed c o m p o n e n t s
Dry matter Crude protein ADF 2 CWC 3 Cellulose
Species
Sheep Goats Sheep Goats Sheep Goats Sheep Goats Sheep Goats
Leucaena levels, %
Mean + SD ~
0
20
40
60
80
50.0 a 50.8 ¢ 66.4 c 68.9 c 52.6 b 56.6 b 55.4 a 58.1 ~ 58.8 b 61.7 b
52.1 a 58.3 b 67.3 ¢ 69.5 c 52.4 b 55.7 b 55.6 d 59.8 ¢ 62.0 ¢ 64.9 b
56.6 c 60.9 b 71.6 b 74.7 b 52.9 b 55.8 b 59.6 ~ 61.6 ~ 62.4 ¢ 65.6 b
59,5 b 68.9 a 75.4 a 77.9" 61.5 a 63.9" 64.8 b 67.7 b
62.5 a 70.3 ~ 76.5 ~ 78.6" 64.5 ~ 66.7 a 71.6 ~ 73.7" 72.8 ~ 73.5"
68.1 b
65.6 b
56.1 _+5.2 61.8_+8.0 71.4_+4.6 73.9 + 4.6 56.8_+5.8 59.7_+ 5.2 61.4_+6.9 64.2_+6.4 64.8 _+5.6 66.3+_4.4
a~aMeans in the same row, not followed by the same letter, are different ( P < 0.05 ). Standard deviation. 2Acid detergent fiber 3Cell-wall constituents. TABLE 4 G r o w t h rate of sheep and goats fed guinea grass with different levels of leucaena Item
Starting weight, kg G r o w t h rates, g / d a y Week 1-8 Week 9-16 Overall
Species
Mean + SD 2
Leucaena levels, % 0
20
40
60
80
Sheep Goats
16.20 7.25
16.10 6.98
16.20 7.10
16.30 7.20
16.10 6.45
16.18+0108 7.00+0.32
Sheep Goats Sheep Goats Sheep Goats
58.41 ¢ 29.43 c 39.43 b 19.29 a 48.92 ¢ 24.36 c
65.15 b 36.31 b 41.71 b 20.93 a 53.43 b 28.62 b
73.18 a 38.10 b 45.46 a 23.42 a 59.32 a 30.76 b
73.45 a 42.50 a 32.27 c 23.76 a 51.86 b 33.13"
ND I 45.20 a ND t 5.44 b ND I 25.32 c
67.55+7.21 38.31 + 6.08 39.72+5.55 18.57+7.57 53.38+4.38 28.44 + 3.67
"bCMeans in the same row not followed by the same letter are different ( P < 0.05 ). Not determined. 2Standard deviation.
During weeks 1-8, growth rate of sheep on 60% (73.4 g/day) and of goats on 80% (45.2 g/day) diet was the highest (P<0.05; Table 4). At 10 weeks of feeding, ~,~heepon 60% and goats on 80% leucaena started to show symptoms of leucaena toxicity which included loss of hair and excessive salivation. Growth rates of both species during weeks 9-16 were lower than in the first period; s]aeep on 60% and goats on 80% leucaena had the lowest growth rates. The overaU growth rate improved ( P < 0.05 ) by addition of leucaena to the
80
J.O. ADEJUMO AND A.A. ADEMOSUN
diets up to the 40% level for sheep and 60% for goats. Sheep grew faster than goats (53.4 vs. 28.4 g/day). DISCUSSION
Based on conventional measures of quality such as CP and ADF, the quality of the diet improved by the addition of leucaena (Table 1 ). Observations in many parts of the world have shown leucaena to be a valuable protein supplement (Jones, 1979; Aii and Stobbs, 1980). DMI increased as the percentage of leucaena in the diet was increased (Table 2 ) in conformity with previous findings with this legume (Jones et al., 1978). They reported low voluntary iniake with cattle ( 1.8 to 2.7% of body weight or 58 to 85 g/kg °'75) when fed a pure leucaena diet. In the present study the most marked depression in intake by sheep and goats occurred when the diet contained more than 40% and 60% of leucaena, respectively. Goats consumed less DM and digested it more completely than did sheep. This is similar to the findings of Huston et al. (1986) who observed that goats consumed 53% less DM, and showed a 9% greater organic matter digestibility compared with sheep. These figures were attributable to the differences in consumption capacity of DM and in retention time, goats having a relatively small reticulorumen and probably a longer retention time. Since the extent of digestion is the net result of rates of digestion and passage (Mertens, 1977), digestibility was greater in goats. DMD values for both sheep and goats increased with increasing level of leucaena in the diets (Table 3 ). The lower DMD value of guinea grass may be due to the fact that stems were included in the test diet. Stem is less digestible as a result of its high degree of cell-wall lignification (Ademosun, 1973 ). High DMD of the high level leucaena diet may be explained in terms of low intake associated with increasing level of leucaena in the diet (Table 2) and extended retention time in the reticulorumen. The longer the retention time the greater is the microbial fermentation of cellulose and hemicellulose which cannot be digested in the small intestine with the animals' own enzymes. The higher digestibilities of all other components of the diets with high leucaena levels (Table 3 ) are a reflection of the high DMD. Rate of growth improved with addition of leucaena to the diet and was highest for sheep on 40% and for goats on 60% leucaena, but decreased thereafter (Table 4 ). Previous investigations have shown that animals on high level (more than 60%) leucaena either maintain weight, lose weight throughout the experimental period or gain weight to begin with and lose weight subsequently (Jones et al., 1978). The low DMI, loss of hair, excessive salivation and reduced weight gain of animals on the high level leucaena diet are thought to be due to chronic mimosine toxicity resulting from prolonged intake ofleucaena (Reis et al., 1975;
LEUCAENA SUPPLEMENT FOR GROWING WAD GOATS
81
Hegarty et al., 1976). Goats tolerated high levels of leucaena (60%) better than sheep and this may be attributable to lower DMI in goats compared with sheep (Table 2) which thus resulted in lower intake of mimosine (0.80 vs. 1.40 g / k g °75). The nutritive value o f a forage is a function o f the daily intake of digestible D M and therefore depends on the quantity o f feed eaten and the digestibility of the feed. The high D M D o f high leucaena diets markedly influenced the NVI (Table 2 ), with the result that the overall nutritive value was higher for 40% leucaena which had the highest DMI. On the other hand, the difference in intake between sheep (65.0 g/kg °75 ) and goats (3 3.9 g/kg °75 ) in this study was high enough to more than offset a lower digestibility by sheep. Growth rate data (Table 4) followed closely those for NVI (Table 2 ), which had higher values for sheep than for goats. It is suggested that for better growth, WAD sheep and goats m a y not be fed diets containing more than 40% and 60% leucaena, respectively or less than 1.0 g mimosine per (kg body weight)O-75. ACKNOWLEDGEMENTS
The International Livestock Centre for Africa funded the project. Thanks are due to the International Institute for Tropical Agriculture, Ibadan, Nigeria, for providing research facilities.
REFERENCES Adejumo, J.O. and Ademosun, A.A., 1985. Effects of planting distance, cutting frequency and height on dry matter yield and nutritive value of Leucaena leucocephala sown alone and in mixture with Panicum maximum. J. Anim. Prod. Res., 6:209-221. Ademosun, A.A., 1973. Nutritive evaluation of Nigerian forages. IV. The effect of stage of maturity on the nutritive value of Panicum maximum. Niger. Agric. J., 10:170-177. Ademosun, A., Jansen, H.J. and Van Houtert, V., 1984. Goat management research at the University of Ife. In: Workshops on small ruminant production systems in the humid zone of West Africa, Ibadan, Intern. LivestockCentre for Africa, pp. 34-37. Aii, T. and Stobbs, T.H., 1980. Solubilityof the protein of tropical pasture species, and the rate of its digestion in the rumen. Anim. Fed. Sci. Technol., 5:183-192. Crampton, R.W., Donefer, E. and Lloyd, L.E., 1960. A nutritive value index for forages. J. Anita. Sci., 19: 538-544. Goering, H.R. and Van Soest, P.J., 1970. Foragefibre analyses (apparatus, reagents, procedures and some applications). Ag. Handbk. No. 379, WashingtonDC., USA. Hegarty, M.P., Court, R.D., Christie, M.D. and Lee, C.P., 1976. Mimosine in Leucaena leucocephala is metabolished to a goitrogen in ruminants. Aust. Vet. J., 52: 490-494. Huston, J.E., Rector, R.S., Ellis, W.C. and Allen, M.L., 1986. Dynamics of digestion in cattle, sheep, goats and deer. J. Anim. Sci., 62: 208. Jones, R.J., 1979. The value of Leucaena leucocephala as a feed for ruminants in the tropics. Wld. Anim. Rev., 31: 13-23.
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Jones, R.J., 1980. Toxicity studies with Leucaena in Hawaii. In: Tropical Crops and Pastures, Division of CSIRO, Australia. Divisional Report, 1979-1980, pp. 101. Jones, R.J., Blunt, C.C. and Nurnberg, B.T., 1978. Toxicity ofLeucaena leucocephala: the effect of iodine and mineral supplements on penned steers fed a sole diet ofleucaena. Aust. Vet. J., 54: 387-392. Keogham, J.M., 1980. Adaptable and productive forage legumes and grasses for more intensive small ruminant livestock systems in the Caribbean. Trop. Anim. Prod., 5: 8-14. Mertens, D.R., 1977. Dietary fiber components: relationship to rate and extent of ruminal digestion. Fed. Proc., 36:187. Reis, P.J., Tunks, D.A. and Hegarty, M.P., 1975. Fate of mimosine administered orally to sheep and its effectiveness as a defleecing agent. Aust. J. Biol. Sci., 28: 495-501. Steel, R.G.D. and Tome, J.H., 1960. Principles and Procedures of Statistics. McGraw-Hill Book Co. New York, U.S.A.