R.M. Njwe and Godwe
Department of Animal Science
Dschang University Centre
Dschang, Cameroon
Abstract
Introduction
Materials and methods
Results
Discussion
References
A comparison of feed utilization and liveweight gain was carried out with adult West African Dwarf sheep fed sodium hydroxide (NaOH) treated dry soyabean pods supplemented with soyabean flour; or fresh Napier grass fed alone or supplemented with soyabean flour.
There were no significant differences in the intake of dry-matter and proximate feed constituents between sheep fed alkali-treated soyabean pods supplemented with soyabean flour and those fed fresh Napier grass plus soyabean flour. Sheep fed only Napier grass consumed significantly more crude fibre but less dry-matter, crude protein, ether extract and nitrogen-free extract than those on the other diets.
The digestibility of dry matter, organic matter, crude fibre and nitrogen-free extract were similar for sheep fed solely on Napier grass and those fed on fresh Napier grass plus soyabean flour. The digestibility of crude protein and ether extract by sheep fed only on Napier grass was significantly lower than the other treatments. All experimental animals had positive nitrogen balance.
Liveweight gain was similar for sheep fed fresh Napier grass supplemented with soyabean flour (77 g/day) and those provided NaOH-treated soyabean pods plus soyabean flour (79 g/day). Animals fed solely on Napier grass gained 41 g/day which was significantly lower than the other treatments.
The commencement of the soyabean project in the Western Province of Cameroon in 1981 has resulted in increased production of the crop. The primary aim of the project was to provide the human population adequate plant protein and cooking oil. However, the livestock sector has a lot to benefit from the project, especially as the cake resulting from oil extraction will be used in livestock rations. Crop residues such as leaves and pods can also be used to feed livestock. The use of these by-products in feeding livestock in the Western Province is of particular significance since the increasing density of the human population is rapidly taking over pasture land for cultivation of food crops. Semi-intensive or intensive small ruminant production is the best alternative available to farmers if this activity has to continue.
The objective of the present study was to compare feed utilization by local sheep fed Napier only, Napier grass plus whole undefatted soyabean flour and NaOH treated dry soyabean pods plus whole undefatted soyabean flour.
Nine adult West African dwarf sheep were selected from the flock of experimental sheep at the Dschang University Centre farm for this study. The flock of sheep had been on adequate plane of nutrition and received adequate health care. The animals were randomly divided into three groups - T1, T2, and T3 in a completely randomised design with group mean weights of 17.73± 2.25, 18.10±1.99 and 18.16±1.92 kg, respectively. The experimental treatments (diets) were as follows:
T1 - Control (fresh Pennisetum purpureum or Napier grass only).T2 - Napier grass plus 250 g ground undefatted soyabean/animal/day.
T3 - Sodium hydroxide-treated dry soyabean pods plus 250 g ground undefatted soyabean/animal/day.
Dry soyabean pods were treated with 4% NaOH solution by sprinkling the solution (800 ml/kg) on the pods using a water sprinkling can and manually mixing them to uniform wetness. The mixture was then covered with polyethylene sheets and jute bags for 24 hours after which the pods were dried in the sun and packed in jute bags until required for feeding animals.
Animals in each treatment were group-fed during the first 5 weeks of the experiment. During the last two weeks they were transferred into individual metabolic cages to facilitate digestibility studies. Freshly cut Napier grass and NaOH-treated soyabean pods were fed to animals twice daily at 9:00 and 16:00 hours, while ground undefatted soyabean was fed once daily at 9:00 hours in a separate feeding trough. The chemical composition of Napier grass, dry soyabean pods and undefatted soyabean are indicated in Table 1. Water and salt licks were provided ad libitum in each cage. The weights of feed fed residues were daily recorded and their dry-matter contents were determined.
The adaptation period in cages was one week. This was followed by a 7-day collection period during which faeces and urine of each animal were collected and measured every 24 hours. Ten percent mercuric chloride solution was used to prevent the loss of ammonia in urine during collection and storage. Urine samples were stored in corked bottles in a deep freezer while daily faecal samples were dried in a laboratory oven for 48 hours at 60°C and stored in polyethelene bags until the time of analysis.
Table 1. Chemical composition of the experimental diets (% dry matter).
|
|
As fed |
On organic-matter basis (%) |
|||||
|
Dry-matter |
Ash |
Organic matter |
Crude protein |
Crude fiber |
Ether extract |
Nitrogen free extract |
|
|
Pennisetum purpureum |
|||||||
|
(Napier grass) |
16.11 |
17.07 |
88.94 |
16.97 |
33.83 |
3.81 |
34.33 |
|
NaOH-treated dry soyabean pods |
92.02 |
12.33 |
87.67 |
17.47 |
30.97 |
3.21 |
36.02 |
|
Undefatted soyabean flour |
90.72 |
5.62 |
94.38 |
37.62 |
10.03 |
23.15 |
23.58 |
Feed and faecal samples were analysed for dry-matter and other feed constituents according to A.O.A.C. methods (1975). Urine nitrogen was analysed using the micro-Kjeldahl method.
Statistical analysis of experimental data was carried out according to the methods of Steel and Torrie (1960) and significant differences between treatments were determined using Duncan's Multiple Range Test (1958).
Table 2 shows the intake of dry matter and nutrients by West African Dwarf sheep. Dry-matter intake was 66.98, 74.82 and 75.31 g/day/W0.75 kg for sheep fed solely fresh Napier grass (T1), Napier grass plus undefatted soyabean flour (T2) and NaOH-treated dry soyabean pods plus undefatted soyabean flour (T3), respectively. Sheep fed only on Napier grass consumed significantly (P<0.05) less dry-matter than the other two treatments. However, the values for animals fed undefatted soyabean flour supplement were similar.
Table 2. Dry-matter and nutrients intake by West African Dwarf sheep on the three experimental diets.
|
Group means |
T1 |
T2 |
T3 |
|
Napier grass with no supplement |
Napier grass + undefatted soyabean meal + undefatted |
NaOH treated soyabean pods soyabean meal |
|
|
Dry matter |
590.20±9.80 |
699.53±8.01 |
701.38±4.64 |
|
g/day/W0.75 kg |
68.98±5.06b |
74.82±5.09a |
75.31±6.44a |
|
Organic matter |
524.86±8.72 |
634.65±7.14 |
630.12±4.07 |
|
g/day/W0.75 kg |
59.57±1015b |
67.83±4.60a |
67.65±5.77a |
|
Crude protein |
100.15±1.66 |
165.50±1.38 |
168.34±0.81 |
|
g/day/W0.75 kg |
11.36±0.86b |
7.70±1.22a |
18.06±1.50a |
|
Crude fibre |
199.66±3.29 |
182.67±2.71 |
169.72±1.39 |
|
g/day/W0.75 kg |
22.66±1.71a |
19.55±1.39ab |
18.23±1.59b |
|
Ether extracts |
22.48±0.37 |
70.50±0.31 |
67.73±0.13 |
|
g/day/W0.75 kg |
2.55±0.19b |
7.54±0.53a |
7.26±0.59a |
|
Nitrogen-free extracts |
202.55±3.36 |
215.72±2.75 |
224.42±1.67 |
|
g/day/W0.75 kg |
22.98±1.74b |
23.95±1.70ab |
24.70±2.08a |
|
Initial liveweight (kg) |
17.775.40 |
18.10±4.00 |
18.16±4.07 |
|
Fir-l liveweight (kg) |
19.93±5.18 |
22.17±3.82 |
22.33±4.25 |
|
Average weight (kg) |
18.852.49 |
20.13±1.84 |
20.16±1.92 |
|
Metabolic weight (W0.75 kg) |
9.01±0.88 |
9.48±0.68 |
9.49±0.69 |
|
Liveweight gain (g/day) |
41±7b |
77±5a |
79±3a |
N.B. Values in a row with same letter script are not significantly different (P>0.05).
There was a direct relationship between dry-matter and crude protein intakes. Crude-protein intake by sheep fed only Napier grass (11.36 g/day/W0.75) was significantly (P<0.05) lower than in sheep fed the grass plus undefatted soyabean flour (17.70g/day/W 0.75) and those fed NaOH-treated soyabean pods plus undefatted soyabean flour (18.06 g/day/W 0.75 kg).
The trends of organic-matter and ether-extract intakes were similar to those of crude protein. Crude-fibre intake by sheep on the control treatment (T1) was significantly (P<0.05) higher than those on T3 (22.66 and 18.25 g/day/W 0.75 kg respectively) but similar to those on T2 (19.55 g/day/W 0.75 kg). The same trend was observed for intake of nitrogen-free extract.
Table 3 shows the digestibility of dry matter and nutrients. The digestibilities of dry matter at 68.82% and
96.67% were similar for sheep fed Napier grass alone and those on Napier grass plus undefatted soyabean flour. Dry-matter digestibility by sheep fed on Napier plus undefatted soyabean flour was significantly (P<0.05) higher than in two NaOH treated dry soyabean pods plus undefatted soyabean flour (66.72%) which was in turn similar to the control treatment.
The highest value of crude-protein digestibility was recorded with animals fed Napier grass and undefatted soyabean flour (83.04%) which was not statistically significant to 79.70% obtained with sheep fed soyabean pods plus undefatted soyabean flour. The value for sheep on the control treatment T1 (74.88%) was significantly (P<0.05) lower than in T2 but not statistically significant (P>0.05) to T3.
Table 3. Percent digestibility of dry matter and other nutrients by West African Dwarf Sheep (%) on the tested diets.
|
Group means % |
Treatments |
||
|
T1 |
T2 |
T3 |
|
|
Dry matter |
68.89±4.23ab |
69.67±1.06a |
66.70±2.36b |
|
Organic matter |
72.53±4.67ab |
73.34±1.22a |
67.77±2.15b |
|
Crude protein |
74.88±2.72b |
83.04±0.43a |
79.70±1.09ab |
|
Crude fibre |
75.29±3.82a |
65.36±3.66b |
62.13±1.58b |
|
Ether extract |
59.18±5.12b |
83.89±2.66a |
83.85±2.73a |
|
Nitrogen-free extract |
70.13±4.78a |
69.18±1.98ab |
60.89±2.51b |
N.B. Values in a row with same letter script are not significantly different (P>0.05).
Crude-fibre digestibility by sheep fed on T1 (95.29%) was significantly (P<0.05) higher than those on T3 (62.13%) and on T2 (65.36%).
On the other hand, ether-extract digestibility by sheep on T1 (58.18%) was significantly (P<0.05) low when compared to T2 and T3 treatments which had similar values (83.89 and 83.85%). The digestibility of nitrogen-free extract by sheep on T1 and T2 (70.13 and 69.18% respectively) were similar. However, T1 was significantly (P<0.05) higher than T3 (60.89%).
Utilization of dietary nitrogen by West African Dwarf sheep is indicated in Table 4. Nitrogen intake and digested nitrogen by animals on T1 were significantly (P<0.05) lower than the other two treatments which were of similar values. This was also the case with nitrogen balance. None of the experimental animals had negative nitrogen balance.
Average daily weight gain by sheep is indicated in Table 2. Live weight gain by animals on T1 (41 g/day) was significantly (P<0.05) lower than those on T2 (77 g/day) or those on T3 (79 g/day). Treatments fed undefatted soyabean flour supplement had similar values.
Table 4. Nitrogen balance of West African Dwarf Sheep on the experimental diets.
|
Group means % |
Treatments |
||
|
T1 |
T2 |
T3 |
|
|
Nitrogen intake (g/day) |
16.03±0.27b |
26.48±0.22a |
26.93±0.13a |
|
Faecal nitrogen (g/day) |
4.04±0.47b |
4.47±0.104b |
5.46±0.35a |
|
Digested nitrogen (g/day) |
11.98±0.33b |
22.01±0.26a |
21.47±0.29a |
|
Urinary nitrogen (g/day) |
10.34±0.56a |
9.83±0.68a |
7.89±0.25b |
|
Nitrogen balance (g/day) |
1.64±0.61b |
12.18±0.42a |
13.58±0.41a |
N.B. Values in a row with same letter script are not significantly different (P>0.05).
Dry-matter intake by West African Dwarf sheep ranged from 66.98 to 75.98 g/day/W0.75 kg. These values are higher than those reported by Namadiga (1983). The increase of dry-matter intake with addition of protein supplement can be attributed to the protein stimulating effect on microbial digestive activity of cellulose. When nitrogenous compounds are deficient in a diet or when only small amounts are present, the growth of rumen microbes in the rumen is greatly inhibited and may lead to inefficient feed utilization.
The improvement of the digestibility of dry-matter, crude protein and ether extract in the present study agrees with those of Briggs and Heller (1942) from feeding large amounts of cottonseed meal in fattening lamb rations.
The decrease in crude fibre digestibility observed during this investigation may be attributed to a substitution effect of readily digestible undefatted soyabean flour.
The fact that all experimental animals were in positive nitrogen balance is a reflection of adequate dietary protein even when Napier grass was the only diet at T1. Animals on fresh Napier grass gained on the average 41 g per day during the experimental period. The high nutritive value of Napier grass at the beginning of the wet season (16.97% crude protein) can be responsible for this performance.
Soyabean pods treated with NaOH and undefatted soyabean flour to sheep promoted weight gains similar to that by animals fed on Napier grass and undefatted soyabean flour. Kpounoho (1986) fed untreated dry soyabean pods with cottonseed meal to local dwarf sheep and observed slight weight losses or at the best body weight was maintained. The utilization on NaOH treated soyabean pods in the present study appears to stimulate higher dry-matter intake and therefore some liveweight gain (79 g/day). Improvement of straw utilization by NaOH treatment has also been indicated by Kategile et al (1979). The optimal treatment rate by NaOH has been reported to be 4% (Klopfenstein et al, 1972 and Hasimoglu et al, 1969).
It may be concluded that supplementation of Napier grass with undefatted soyabean flour feed intake gave adequate levels of improved digestibility and weight gain compared to the
Napier grass fed alone. It is possible to maintain sheep on dry soyabean pods treated with NaOH solution and undefatted soyabean flour particularly during the dry season when grass of good nutritive value is scarce.
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Duncan, D.B. 1958. Multiple Range and Multiple F. test. Biometrics (1): 1-42.
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Kategile, J.A. and Frederikson, J.H. 1979. Effect of level of NaOH-treatment and volume of solution on the nutritive value of maize cobs. Anim. Feed Sci. Technol. 4:1-15.
Klopfenstein, T.J.; Krause, V.E.; Jones, M.J. and Walter, W. 1972. Chemical treatment of low quality roughages. J. Anim. Sci. 35:418.
Kpounoho, I. 1986. Utilization and nutritive value of soyabean husk with or with no cotton seed cake by sheep. Final year memoir. Dept. of Animal Science, ENSA, Dschang University Centre, Cameroon.
Namadiga, P. 1983. The protein requirements of young blackbelly sheep. Final year memoir. Dept. of Animal Science, Dschang University Centre, Cameroon.
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