F. O. Olubajo, ¹ M.M. Asonibare ¹ and
E. O. Awolumate ²
¹ Department of Animal Science, University of Ibadan
Ibadan, Nigeria² Cocoa Research Institute of Nigeria (CRIN), Idi-Ayunre
Ibadan, Nigeria
Abstract
Introduction
Materials and methods
Results
Discussion
Conclusion
Acknowledgements
References
Six digestion trials were conducted with West African Dwarf bucks and Dwarf rams to study the utilisation of cocoa-pod silage and of graded levels of cocoa pod - elephant grass silages consisting of the following treatments : (1) 100% elephant grass silage (control); (2) 50:50; (3) 25:75; (4) 15:85; (5) 10:90, grass : cocoa-pod (fresh basis), respectively; and (6) 100% cocoa-pod silage.
The cocoa-pod silage contained approximately 5.7% crude protein (CP), 22% crude fibre (CF) and a mean energy value of 4.4 kcal/g in contrast to the grass silage with a composition of 4.8% CP, 32% CF and 4.7 kcal/g of energy.
Results indicated that on metabolic-weight basis more digestible dry matter (DDM; P<0.01), digestible energy (DE, P<0.001) cellulose or hemicellulose was consumed from the control diet. Intake of digestible nitrogen was also significantly (P<0.001) higher for the control diet than for any of the silages. More nitrogen (N) was excreted when either treatment 2 or treatment 3 was fed indicating that the N content of these treatments was metabolised less efficiently while N - retention was similar and slightly positive for all treatments.
Sheep consumed more (P<0.001) DM and energy, and significantly (P<0.05) higher DM and DE than goat. Both species were similar in their intake of digestible N. However, more N (P <0.01) was excreted by sheep showing that this species metabolised the N content of the diets less efficiently. Nitrogen retention by both species was similar. Additional sources of protein supplement are required in all diets for better performance.
Cocoa-pod is a by-product of the cocoa harvesting industry. It forms about 80% of the cocoa fruit and it is essentially a waste product except for the negligible amount used in the manufacture of local soap. Oguntuga (1975) and Awolumate (1982) have given chemical composition of cocoa-pod while Adeyanju et al (1975a,b) have reported the use of the dried pod as a substitute for maize in swine ration, in milk production of dairy cows and in the maintenance ration of sheep and goat or at various levels in the starter diets of chicks up to six weeks of age (Adegbola et al 1977).
The object of this investigation was to study the nutritive and replacement values of fresh cocoa-pod silage and cocoa pod - grass silage.
Silage preparation
The following silage treatments were prepared from fresh cocoa pods and elephant grass (Pennisetum purpureum) at a fairly advanced (full flower) stage:
1. 100% elephant grass (Pennisetum purpureum as control)2. 50% grass + 50% cocoa-pod
3. 25% grass + 75% cocoa-pod
4. 15% grass + 85% cocoa-pod
5. 10% grass + 90% cocoa-pod
6. 100% cocoa-pod
For each batch of silage preparation the grass which was at the fairly advanced stage of growth was cut fresh, chopped into 2-6 cm lengths. Cocoa-pods were collected immediately the beans and mucilage were removed from the fruits, chopped into small bits and both grass and pods were weighed (on wet basis), thoroughly mixed and made to pass through a chopper and packed according to the ratio required in double-layered polythene bags fitted into 198-litre drums. After compressing thoroughly the content of each drum was sealed, weighted down with about 15-20 cm layer of dry earth and heavy stones and ensiled for at least 12 weeks before it was fed.
Representative samples were taken from each batch of fresh mixture for dry-matter determination and proximate analysis.
Digestion trials
Six animals consisting of three West African Dwarf bucks weighing between 20.0 and 23.2 kg (mean 21.4 ± 1.34 kg) and three West African Dwarf rams ranging from approximately 18.2 to 32.3 kg (mean 23.5 ± 6.26 kg) were used in the digestion trials.
The digestibility trial of the grass silage (control diet) consisted of 12 days of preliminary and seven days of collection periods while each subsequent feeding trial was of seven days of preliminary and seven days collection duration.
During the digestion trials each experimental animal housed in a digestibility crate designed for easy collection of urine, was harnessed with a faeces-collection bag four days before the commencement of actual collection. Each animal group was used as its own control and for each of the other treatment digestion trials.
The top 4 - 5 cm layer of silage in each drum was discarded and representative samples were taken from top to bottom, cut into small bits and after mixing well, subsamples were taken for dry-matter and pH determinations and for chemical analysis. During the first preliminary period each animal was offered 2.73 kg of the test diet on the first day and was increased as necessary to allow for ad libitum intake in subsequent days. During collection period the amount offered was restricted to about 95% of the mean intake of each animal during the preliminary period.
Each day's feed was offered between 0800 and 0830 hours and at 1600 hours. Fresh tap water and salt lick was supplied ad libitum. Faeces from each animal was collected twice daily just before the morning and afternoon feeds were offered, weighed, mixed thoroughly and approximately 20% from morning and afternoon collections composited and taken to the laboratory and treated like the samples of feed offered. Orts from the previous day's feed was collected once daily just before offering morning feed, weighed, mixed and representative samples were taken for dry-matter determination. Urine from each animal was collected and with 10 ml of H2SO4 in the last three days of each collection period. Total volume of urine excreted by each animal was measured every morning and 10% aliquot taken and bulked for the three-day period for nitrogen and energy determination. The urine samples were stored in a deepfreezer at -5°C until required for analysis.
Analytical procedures
Dry-matter of the silages, faeces, and ort was determined by drying weighed duplicate samples in a forced air electric oven at 90°C to constant weight. The pH was determined from squeezed silage juice samples by means of Radiometer Copenhagen glass electrode pH meter. Gross energy (GE) of feed and faeces was determined in a Gallenkamp ballistic bomb calorimeter using benzoic acid as standard. GE in urine was estimated by drying a known volume soaked in a pre-weighed ashless filter paper over P2O5 in a desiccator, re-weighed after drying, followed by bombing. The AOAC (1970) procedures were used for the determination of the proximate constituents in the feed, faeces and urine. Acid detergent lignin was estimated according to Van Soest (1963) and cellulose by the method of Crampton et al (1960). Statistical analyses were based on factorial design as described by Steel and Torrie (1960) with the six treatments serving as the main treatments, the species as subtreatments and the animals as replicates. Metabolisable energy was estimated by multiplying digestible energy by a factor of 0.81 (ARC, 1965).
The chemical composition of the pre-ensiled mixtures and of the resulting silages from them is shown in Table 1 and 2 respectively. The data in Table indicated that the mean dry matter (DM) content of the elephant grass at harvest was slightly below the 30% or above known to result in silage of good quality. Increased replacement of the grass with fresh cocoa-pod led to decreased (DM) content of the pre-ensiled mixtures due to the high moisture content of the fresh cocoa pod. Replacement of the grass with cocoa-pod resulted in an improvement in the N content of the silages by approximately 23.8% up to the 75% cocoa-pod inclusion and was slightly lower in the other treatments. Similarly, ensilage of cocoa-pod with elephant grass led to an increase in the nitrogen-free extract (NFE) but to a decrease in CF. lignin, and other constituents of the silages. Addition of cocoa-pod to grass did not improve fermentation of the grass as there was little or no difference between the pH values of the grass silage (control) and those of grass-cocoa pod silages. Ensiling cocoa-pod for a period of 12 weeks (or longer) showed little or no change.
Table 1. The proximate composition of pre-ensiled treatments (%).
|
|
Treatment |
|||||
|
1 |
2 |
3 |
4 |
5 |
6 |
|
|
100% grass |
50/50 |
25/75 |
15/85 |
10/90 |
100% |
|
|
Dry matter |
28.84 |
22.55 |
19.02 |
18.84 |
20.99 |
18.20 |
|
Organic matter |
85.57 |
88.01 |
92.09 |
91.25 |
89.16 |
87.35 |
|
Ash |
14.43 |
11.99 |
7.91 |
8.75 |
10.84 |
12.65 |
|
Crude protein |
7.65 |
7.62 |
7.51 |
7.49 |
7.59 |
6.46 |
|
Ether extract |
2.35 |
1.95 |
1.93 |
1.75 |
0.94 |
0.90 |
|
Crude fibre |
34.31 |
31.24 |
29.28 |
28.09 |
27.16 |
24.38 |
|
NFE |
41.26 |
47.20 |
53.37 |
53.92 |
53.47 |
55.62 |
|
Lignin |
8.23 |
7.60 |
7.18 |
7.85 |
6.44 |
2.29 |
|
Hemicellulose |
25.21 |
21.95 |
20.76 |
18.12 |
22.03 |
22.12 |
|
Cellulose |
30.90 |
26.62 |
26.75 |
24.51 |
24.78 |
25.31 |
|
Energy (kcal/g) |
4.730 |
4.786 |
4.993 |
4.809 |
4.977 |
4.575 |
Table 2. Proximate composition of the silages (%).
|
|
Treatment |
|||||
|
1 |
2 |
3 |
4 |
5 |
6 |
|
|
100% |
50/50 |
25/75 |
15/85 |
10/90 |
100% |
|
|
grass |
|
|
|
|
cocoa-pod |
|
|
Dry matter |
19.16 |
16.94 |
22.22 |
20.21 |
18.09 |
14.56 |
|
Organic matter |
83.05 |
85.04 |
89.70 |
88.18 |
86.21 |
82.52 |
|
Ash |
16.95 |
14.94 |
10.30 |
11.82 |
13.79 |
17.48 |
|
Crude protein |
4.78 |
5.92 |
5.92 |
5.46 |
5.69 |
5.69 |
|
Ether extract |
2.10 |
1.55 |
1.52 |
1.10 |
0.77 |
0.75 |
|
Crude fibre |
32.21 |
29.35 |
27.24 |
26.10 |
25.12 |
22.40 |
|
NFE |
43.96 |
48.22 |
55.02 |
55.52 |
54.63 |
53.68 |
|
Lignin |
8.21 |
7.56 |
7.12 |
6.80 |
6.40 |
5.20 |
|
Hemicellulose |
24.10 |
21.30 |
19.91 |
18.7 |
21.56 |
21.32 |
|
Cellulose |
36.01 |
28.50 |
30.00 |
29.00 |
28.50 |
30.50 |
|
Energy (kcal/g) |
4.714 |
4.675 |
4.984 |
4.592 |
4.837 |
4.374 |
|
pH |
5.35 |
5.25 |
5.08 |
5.10 |
5.12 |
7.70 |
Feed and nutrient intake
On metabolic-weight basis (g/kg W0.75) mean daily consumption of DM and of DDM was significantly (P<0.01) higher for the control diet than for either the cocoa-pod silage or any of its combinations with grass (Table 3). The pattern of intake of digestible cellulose or hemicellulose was similar to that of dry-matter intake. The data in Table 3 also indicated that the mean DE. value of 212 kcal/kg W0.75 for the control diet was significantly (P<0.001) higher than the mean value of 73 kcal/kg W0.75 for the cocoa-pod silage. While the energy content of the grass silage was approximately 73% digestible the corresponding value for the cocoa-pod silage was approximately 33%.
The significantly (P<0.01) higher intake of dry-matter from the control diet by the experimental animals could be due to the intake of significantly higher (P<0.001) digestible energy from this diet (Table 3) when compared to any of the silages resulting from its combinations with the cocoa-pod. Blaxter (1961) have suggested that digestibility is an important determinant of ad libitum intake of feeds and that the amount of roughage consumed by sheep fed ad libitum, is closely related to the energy digestibility of the feed and that increased energy digestibility leads to increase in dry-matter intake.
The significantly lower energy and digestible energy intake values obtained for the cocoa-pod silage and of the 15:85, and 10:90 grass/cocoa-pod silage was probably due to the lower energy value and the high moisture content of the cocoa-pod in these silages. Intake of energy from cocoa-pod silage which was 76% of the intake from the control diet resulted in only 34% of the digestible-energy intake of the latter.
Table 3. Mean daily intake of nutrients (g/kg W 0.75) by experimental animals.
|
Nutrient |
Treatment |
||||||
|
1 |
2 |
3 |
4 |
5 |
6 |
S.E |
|
|
Dry matter |
62.7a |
549bc |
57.0b |
45.6d |
48.8de |
50.9ce |
2.3*** |
|
Digestible dry matter |
40.7a |
25.9b |
27.7b |
22.6b |
199b |
26.7b |
5.46** |
|
Crude protein |
3.0b |
3.3ab |
3.9a |
2.5c |
2.9bd |
2.9b |
0.12*** |
|
Digestible crude protein |
1.4a |
1.0b |
0.9bc |
0.5d |
0.6cd |
0.4d |
0.18** |
|
Cellulose |
22.5a |
15.6b |
11.1b |
13.2c |
13.8c |
15.5b |
0.85*** |
|
Hemicellulose |
8.3a |
5.0b |
5.2b |
2.6cd |
2.6cd |
3.3bd |
0.12*** |
|
Energy (kcal/kg W 0.75) |
292a |
257bd |
273ab |
209c |
236cd |
222c |
14.61*** |
|
DE (kcal/Kg W0.75) |
212a |
124b |
138b |
101c |
101c |
73c |
15.91*** |
|
ME (" ") |
171a |
100b |
112b |
82b |
82b |
59b |
192*** |
Values in the same row followed by the same letter are not significantly different.
** = P<0.01; *** P<0.001.
Nitrogen utilization
Though there was a significant (P<0.05) improvement of approximately 13% in the N intake of the 25:75 grass/cocoa-pod silage over that of the control diet (Table 4), intake of this nutrient in other silages with higher proportion of cocoa-pod was depressed. Similarly, substitution of grass with cocoa-pod did not significantly (P>0.05) depress the digestible N up to the 75% level of inclusion but significantly depressed digestible N at (P<0.01) about 75% level. Cocoa-pod contained the lowest amount of N. The degree of depression rose as the proportion or level of cocoa-pod increased. Similarly results of depressed intake of dry-matter and digestible nutrients when cocoa-pod was substituted for maize in either sheep and goat, swine or beef cattle rations, have been reported (Adeyanju et al, 1975 a,b; Fraps, 1946; Adeyanju et al, 1977; Bateman et al, 1967; Glover et al, 1958).
Table 4. Nitrogen utilization by sheep and goat.
|
|
Treatment |
||||||
|
1 |
2 |
3 |
4 |
5 |
6 |
S.E. |
|
|
N Intake (g/kg W0.75) |
0.48ab |
0.52c |
0.54c |
0.40de |
0.44ae |
0.46a |
0.2*** |
|
Output |
|||||||
|
Faecal N (g/kg W0.75) |
0.26b |
0.37 |
0.39a |
0.32ab |
0.35a |
0.39a |
0.04*** |
|
Urine N (g/kg W0.75) |
0.118a |
0.096ab |
0.118a |
0.053ab |
0.055ab |
0050bc |
003** |
|
Absorbed N (g/kg W0.75) |
0.22a |
0.16ac |
0.15ac |
0.08c |
0.10b |
0.07b |
0.04** |
|
N retained (g/kg W0.75) |
010a |
005a |
0.03a |
0.03a |
0.04a |
0.02a |
0.04 N.S. |
|
Retention as % of absorption |
45 |
31 |
20 |
38 |
40 |
29 |
- |
Values in the same row followed by the same letter script are not significantly different.
** = P<0.01; *** = P<0.01.
Nitrogen retention was positive, low and similar (P>0.05) for all treatments studied. Approximately 45% of N absorbed and 21% of N consumed was retained by the experimental animals when fed the control diet while the corresponding values for cocoa-pod silage were approximately 29% and 4% respectively. The relatively low N utilization from cocoa-pod silage of from any of its silage combinations could not be attributed to its concentration either in the pre-ensiled mixtures or in the resulting silages.
Sheep consumed more (P<0.001) dry-matter, nitrogen and energy and higher energy (P<0.05) than goat. Both species were similar in their intake of digestible N.
The low dry-matter (DM) content obtained for elephant grass is in agreement with the results of other workers elsewhere which have consistently shown that at between 4 and 8 weeks of regrowth the DM content of elephant grass is below 20% and at 24 weeks, when in full bloom, a mean of 36.7% was obtained in the humid zone of south-western Nigeria (Oyenuga, 1957; Olubajo and Oyenuga, 1974; Olubajo, 1981). The depressed dry-matter content of the pre-ensiled grass-cocoa-pod mixtures was as a result of the high moisture content of the cocoa-pod when compared to that of elephant grass (control), while cocoa-pod replacement led to an increase in nitrogen-free extract as a result of the higher content of this nutrient in the cocoa-pod. The slight decrease in the crude protein content of the ensiled products may be attributed to loss of volatile nitrogen products (such as ammonia) from protein fermentation. The high pH values of the silages are attributable to the limited available soluble carbohydrates in the ensiled mixtures as well as to the high ash content (alkali-forming cations Ca++, K+ and Na+) in the pre-ensiled mass most especially in the 100% cocoa-pod which may have inhibited or lowered the activities of acid-forming lactobacilli thereby limiting the level of lactic acid production in the ensiled mass.
The relatively low N utilization of cocoa-pod silage or of any of its grass silage combinations could not be attributed to its concentration either in the pre-ensiled mixtures or in the silages when compared with that of the control diet as its concentration was similar in all the treatments. It could however, be due to the presence of as yet unidentified inhibitors in the cocoa-pod. Awolumat (1982) was of the opinion that pesticides used in plant protection, tannins, theobromine and polyphenols if present in cocoa-pod can affect the voluntary intake, digestion and metabolism in animals. They also decrease palatability and digestibility of protein. Chlorogenic acid present in cocoa components is found to cause motor activity in ruminants and rats affecting decreased weight and feed conversion efficiency. This may account for the low values obtained for the cocoa-pod diets. The similarity in the digestible nitrogen and digestible dry-matter intake by sheep and goat obtained in the present study confirms similar reports by Adeyanju et al (1976), while the report of Burroughs et al (1950) showed that sheep utilized crude protein in cocoa-pod rations better than goat. They also reported higher apparent digestibilities of all feed nutrients studied, by sheep.
However, more nitrogen (P<0.01) was excreted by sheep in the present investigation, showing that sheep metabolised N content of the diets less efficiently. Nitrogen retention by both species was similar (P<0.05).
Though the period for each digestion trial was too short for any meaningful appraisal of the effect of the various diets on the live weight changes of the experimental animals, the limited data obtained during the experimental period indicated that despite the slight positive nitrogen retention by each species of animals from all treatment diets goats made significantly (P>0.01) more live weight gain on the average than sheep (+0.012g vs - 0.05g/kg W0.75) per head per day respectively.
The high moisture content of cocoa-pod and low soluble carbohydrate content resulted in silages of high pH and high moisture content.
Cocoa-pod kept for more than 24 hours becomes mouldy under humid conditions and results in mouldy, unpalatable silage when ensiled alone or in combination with grass.
These and the possibility of its commercial use as a source for furfural production may be the major constraints for its use as a source of animal feed in the future just as molasses has been diverted to the production of alcoholic drinks thereby making its cost prohibitive for inclusion in animal feed rations.
The senior author wishes to express his profound gratitude to the Senate Research Grant Committee of the University of Ibadan for providing the funds for this study and also to acknowledge the support given by the authorities and members of staff of the Cocoa Research Institute of Nigeria (CRIN), Idi-Ayunre, Ibadan, for providing the cocoa-pods and the facilities for making the silages and in the determination of the pH of the silages.
Adegbola, A.A. and Omole, T.A. 1973. A simple technique for preparing discarded cocoa bean meal for use in livestock feed. Nig. Agric. J. 10: 72 - 81.
Adeyanju, S.A.; Oguntuga, D.B.A.; Ilori, J.O. and Adegbola, A.A. 1975a. Cocoa husk in poultry diets. Mall Agric. Res. 4: 131-136.
Adeyanju, S.A.; Oguntuga, D.B.A.; Ilori, J.O. and Adegbola, A.A. 1975b. Cocoa pod in maintenance rations for sheep and goats in the tropics. Nut. Rep. Int. 11: 351 857.
Adeyanju, S.A.; Akinokun, O. and Ariyibi, O.O. 1976. Further studies on the utilizations of cocoa pod in ruminant rations. Nig. J. Anim. Prod. 3: 139-143.
Adeyanju, S.A.; Oguntuga, D.B.A.; Sonaiya, E.B. and Eshiett, N. 1977. Performance of chicks on diet containing graded levels of cocoa pod. Nut. Rep. Int. 15: 165-170.
AOAC (Association of Official Analytical Chemists). 1970. Official methods of analysis, 11th ed. AOAC, Washington, D.C.
ARC (Agricultural Research Council). 1965. The nutrient requirements of farm livestock. No. 2. Ruminants. Printed by Her Majesty's Stationery Office, London, UK.
Awolumate, E.O. 1982. Chemical composition and potential uses of processing wastes from some Nigerian cash crops. Cocoa Research Institute of Nigeria. Annual Report. Ibadan, Nigeria.
Bateman, J.V. and Fresnillo, B. 1967. Digestibility of Theobroma cocoa when fed to calves. J. Agric. Sci. 68: 2325.
Blaxter, K.L.; Wainman, F.W. and Wilson, R.S. 1961. The regulation of food intake by sheep. Anim. Prod. 3: 5161.
Burroughs, W.; Long, J.; Gerlaugh, P. and Bethke, R.M. 1950. Cellulose digestion by rumen microorganisms as influenced by cereal grains and protein rich feeds commonly fed to cattle using artificial rumen. J. Anim. Sci. A 9: 523 530.
Crampton, E.W.; Donefer, E. and Lloyd, L.E. 1960. A nutritive value index for forages. J. Anim. Sci. 19: 538-544.
Fraps, G.S. 1946. Digestibility and production coefficients of poultry feeds. Texas Agric. Sta. Bull. 372.
Glover, J. and Dutchie, D.W. 1958. The apparent digestibility of crude protein by non-ruminants and ruminants. J. Agric. Sci. 51: 289-293.
Oguntuga, D.B.A. 1975. Some physical and chemical characteristics of the pod husk of F3 Amazon, Innitario and Amelonado cocoa in Nigeria. Ghana J. Agric. Sci. 8:
Olubajo, F.O.; Van Soest, P.J. and Oyenuga, V.A. 1974. Composition and digestibility of four tropical grasses grown in Nigeria. J. Anim. Sci. 38: 149-153.
Olubajo, F.O. 1981. The feeding value of two tropical grass and grass pineapple pulp silages. World Rev. Anim. Prod. VII: 37-42.
Oyenuga, V.A. 1957. The composition and agricultural value of some grass species in Nigeria. Emp. J. Exp. Agric. 25:237-255.
Steel, R.G.D. and Torrie, J.H. 1960. Principles and procedures of statistics. McGraw-Hill Book Company, Inc. London.
Van Soest, P.J. 1963. Use of detergents in the analysis of fibrous feeds. II. A rapid method for the determination of fibre and lignin. Assoc. Off. Anal. Chem. J. 46: 829-835.
