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The effect of supplementation of cassava peel (CP) diets with graded levels of palm kernel cake (PKC) on the performance of growing Djallonké sheep

A.K. Tuah1, E.R. Ørskov2, F.Y. Obese1, D.B. Okai1 and J.F.D. Greenhalgh3

1Department of Animal Science, Faculty of Agriculture University of Science and Technology, Kumasi, Ghana

2Rowett Research Institute, Aberdeen, Scotland, U.K.

3Gilfach, Rowen, Conwy, Gwynedd, LL32 8TS, U.K.

Materials and methods


Djallonké sheep were fed an ad libitum basal diet of cassava peel (CP) supplemented with graded levels (0, 50,100,150 and 200 g/head per day) of palm kernel cake (PKC). This study reports the effects of this dietary supplementation on feed intake, bodyweight changes, water intake and mortality. The supplementary levels corresponded to dietary treatments 1-5, respectively. The mortality rates of the animals were 20, 20, 40, 50 and 0% for diets 1,2,3,4 and 5, respectively. Mean daily intakes of CP, CP and PKC supplements and water were not significantly (P>0.05) affected by dietary treatments or sex. There was an increase (P<0.01) in the intake of PKC as the level of supplementation increased. Generally the intake of PKC was low. This might be attributable to poor quality resulting from its preparation. In another study the degradation characteristics of the two feedstuffs were studied using the nylon bag technique. The insoluble but slowly degradable portion of the PKC was low (about 16%).

Effet de la complémentation de rations à base de pelures de manioc avec du tourteau de palmiste sur les performances du mouton Djallonké


Cette étude présente les effets de rations à base de pelures de manioc complémentées par du tourteau de palmiste (0, 50, 100, 150 et 200 g/tête/jour) sur l'ingestion, l'évolution pondérale, la quantité d'eau ingérée et la mortalité de moutons Djallonké nourris ad libitum. Les niveaux de complémentation correspondaient respectivement aux traitements alimentaires 1, 2, 3, 4 et 5. La mortalité des animaux était de 20, 20, 40, 50 et 0% pour les traitements 1, 2, 3, 4 et 5, respectivement. Les traitements et le sexe des animaux n'avaient pas d'effet significatif (P>0,05) sur la consommation journalière moyenne des pelures de manioc ou des pelures de manioc complétées par du tourteau de palmiste, ni sur la quantité moyenne d'eau ingérée par jour. La consommation du tourteau de palmiste augmentait (P<0,01) avec l'accroissement du niveau de complémentation mais demeurait faible d'une manière générale, probablement en raison de sa mauvaise qualité, elle-même imputable à une préparation défectueuse. Une autre étude a porté sur l'examen des caractéristiques de la dégradation de ces deux aliments au moyen de la technique des sachets en nylon. La portion insoluble mais faiblement dégradable du tourteau de palmiste était peu importante (près de 16%).


It is the policy of the Government of Ghana to increase the production of small ruminants to meet the animal protein requirements of the population. The Ministry of Agriculture (1988) envisaged an increase in the population of goats from about 1.9 million in 1987 to about 9.2 million by the year 2000; the population of sheep was expected to increase from about 2 million in 1987 to about 6.4 million by the year 2000. The main producers of small ruminants in Ghana are small-scale rural farmers. It is mainly these farmers who will be expected to increase their production. They, however, have serious problems feeding their animals. Increased pressure on the land has forced people to farm near their villages within walking distances of animals. During the cropping season animals are therefore kept in pens for most of the day. They are allowed to graze later in the afternoon, when they are less likely to travel outside the villages and damage the crops.

In the dry season the quality of the sparsely scattered forages is also poor, especially in the northern savanna zones of the country. The rural farmers, unlike the urban backyard farmers, are-not able to purchase completely mixed diets or feed ingredients to feed their animals. They have to rely on crop residues generated from their own farms and also foliage of multi-purpose trees, shrubs and grasses which they harvest from their farms or roadsides. The commonest crop residue fed to animals by farmers in both the south and north of the country is cassava peel (CP), although peels of plantain, yam and cocoyam are also used by farmers in the south.

About 3,327,000 metric tons of cassava is produced in Ghana per year (FAO, 1990) and with an extraction rate of about 20% (Kossila, 1984), about 665,400 metric tons of CP are produced in the country in a year. CP, however, has low nitrogen (Tuah, 1990) and mineral (Adegbola et al, 1988) contents. The objective of this study was therefore to investigate the effects of supplementing CP diets with graded levels of PKC as a protein source on the performance of young growing Djallonké sheep. PKC is available in most villages in the southern forest zone of the country but is not used at present as animal feed.

Materials and methods

Experiment 1


The PKC used in the trial was obtained from a palm oil production factory at Ahodwo, a suburb of Kumasi, near the University of Science and Technology, Kumasi, Ghana. To extract the oil from the kernels, they were first dried, then roasted and ground through a hammermill (about 1 mm sieve). The ground materials were boiled with water and the supernatant oil skimmed off. The residue kernel cake was dried in the sun.

The CP were obtained from a "garri" processing factory in the city of Kumasi. They were peels of mixed varieties of cassava. The peels sometimes had some cassava tuber pieces in their linings. They were sun-dried before being fed to the animals.

Animals, housing, management and feeding

A growth rate study of twenty three young Djallonké sheep of both sexes was carried out at the Department of Animal Science, University of Science and Technology, Kumasi, Ghana. The animals had a mean live weight of approximately 12 kg and were dipped and dewormed at the start of the experiment. They were weighed after 18 hours without food. The animals were kept in individual pens measuring 1 x 3 m on wooden slatted floors in a building described by Tuah et al (1985). They were randomly allocated to five dietary treatments. Treatment groups were balanced for sex of animals. Dietary treatments 1-5 corresponded to five graded levels of PKC supplements to the basal CP diet (0, 50, 100, 150 and 200 g/head per day). The animals were fed daily at 0800 from wooden troughs described by Tuah et al (1985). The troughs for those animals which received the PKC supplements were partitioned into two compartments with pieces of wood. Water was offered ad libitum at 0800 daily. The animals were allowed two weeks to adjust to their respective diets before data began to be collected. Feed and water intake and bodyweight changes were monitored. Leftover feed and water were measured every morning before fresh feed and water were provided. Samples of feed and oats or leftovers were taken once a week and kept for analysis. The animals were weighed every two weeks after 18 hours without food throughout the 12-week study.

Experiment 2

In sacco degradation of CP and PKC

This study was undertaken at the Rowett Institute, Aberdeen, Scotland. Samples of CP and PKC weighing about 3 g each were put in nylon bags. They were then incubated in the rumens of three fistulated wethers to measure degradability of dry matter at various incubation periods. The wethers had a mean body weight of 58 kg. The incubation periods were 4, 8, 16, 24, 48, 72 and 96 hours. The type of bags and the incubation procedures were the same as described by Tuah et al (1986). The sheep were fed 700 g/head per day at 0900 h and 1600 h of a diet containing (per kg): 500 g hay; 300 g barley; 100 g molasses; 91 g fishmeal; 5 g dicalcium phosphate; 3 g NaCl; and 1 g mineral-vitamin premix. The mineral-vitamin premix contained (per kg): 185 g calcium; 104 g magnesium; 2250 mg cobalt; 44,000 mg manganese; 36,400 mg zinc; 1300 mg iodine; 100 mg selenium; 10,000,000 iu retinol; 2,000,000 iu vitamin D3; and 40,000 iu alphatocopherol.

CP and PKC were ground in a 3 mm sieve and triplicate samples of each were soaked in warm water (about 39-39°) for one hour. The samples were subsequently washed in a washing machine as was done for the CP and PKC samples incubated in the rumens of the sheep. The washing losses were determined after drying the samples in an oven at about 70°C for 48 hours. The equation of Ørskov and McDonald (1979), p = a + b(1-ect), was used to describe the course of degradation of the feeds.

Calculation of energy intake, maintenance energy and rumen degradable nitrogen requirements

It was assumed that the PKC supplied negligible amounts of metabolisable energy (ME). Thus the calculation of ME intakes was based on the energy from the CP only. It was also assumed that all the nitrogen in the CP was degradable in the rumen and that nitrogen in PKC was only 16% degradable in the rumen.

The fractional outflow rate of the particles of CP was assumed to be 0.04/h. The apparent digestibility coefficient of dry matter of the CP was then estimated to be 0.58, based on the in sacco degradation characteristics of the peels. The ME content of the CP was estimated using the formula MJ ME/kg dry matter = 0.156 x DOM, given by Roy et al (1977), where DOM is the digestive organic matter per kg of dry matter. The estimate of the ME content of CP (9 MJ ME/kg dry matter) may have been overestimated because instead of using the in vivo content of dry matter, digestible dry matter (DDM) content was used. The mean ME intakes of the animals were then calculated from their mean daily dry matter intakes. The rumen degradable nitrogen (RDN) requirements of the animals were calculated using the requirement value of 1.33 g N/MJ ME (ARC, 1984). The maintenance energy requirement for the animals was assumed to be similar to the requirement of the temperate breeds for which Ørskov and McDonald (1970) reported a value of 420 KJ/kg W0.75/day

Chemical analysis

The dry matter contents of the CP and PKC and the fat content of PKC were determined according to the methods of AOAC (1980). The nitrogen contents of the two feedstuffs were determined by the Kjedahl method (AOAC, 1980).

Statistical analysis

The intake of CP, PKC, CP + PKC and water were subjected to statistical analysis using the 2-way analysis of variance (Steel and Torrie, 1980).


Chemical composition of the feedstuffs

The dry matter contents of the CP and PKC were 84.49 and 86.67%, respectively. The nitrogen contents of the CP and PKC were 5.44 and 33.53 g per kg dry matter, respectively. The PKC contained 10.2 g fat per kg dry matter.

Degradation characteristics of the feedstuffs

The degradation characteristics of the feedstuffs are shown in Figure 1. The rate and level of degradation of CP were higher than PKC after 16 hours of incubation. Before then, the apparent degradability of PKC was better than that of CP. This may be attributed to particle size differences.

Feed and water intake, bodyweight changes and general performance of the animals

The performance of the animals was generally poor resulting in the deaths of some animals as shown in Table 1.

The mean intake of water, combined CP and palm kernel cake and CP alone were not significantly (P>0.05) affected by dietary treatments or sex. The intake of the palm kernel supplement was, however, significantly (P<0.01) affected by dietary treatment. As the level of supplementation increased, the intake of the PKC increased. The mean intake of CP alone was 63 g/kg w0.75 per day for males and 61 g/kg W0.75 per day for females. For the PKC, the mean intake values were 7 and 6.5 g/kg w0.75 per day for males and females, respectively. The mean daily water intakes were 269 and 284 ml/kg W for the males and females, respectively. The changes in the body weights of the animals which survived throughout the 12-week study period did not follow any consistent trend. Two of the animals on Diet 1 and one each of the animals fed Diets 3, 4 and 5 maintained their body weights. Two of the animals fed Diet 5 and one of those fed Diet 1 lost weight. All the other animals gained weight (range 0.5 to 2.0 kg/84 days).

Figure 1. In vitro dry matter degradability values of cassava peels and palm kernel cake at various incubation periods.

Two animals each from Diets 3 and 4 died while one animal each died from those fed Diets 1 and 2.

Table 2 shows the calculated energy intake, maintenance energy requirements and rumen degradable nitrogen requirements of the animals. The total nitrogen supplied by the PKC for the levels of intake registered is also shown in Table 2.


Generally the performance of the animals was poor because of rumen degradable nitrogen deficiency in their diets. This deficiency was not alleviated by supplementing the CP with PKC as the intake of PKC supplements was generally very low. This low intake could not be attributed to the fat content of PKC which was also low (10.2 g/kg dry matter), but could be attributed to the low palatability of PKC (McDonald et al, 1988) Yussof (1985) reported high intakes of diets containing PKC by cattle, but the cake was completely mixed with the other ingredients. The objective of this study would have been defeated if the two ingredients had been ground and mixed, as rural farmers would not have adopted the feed package because of the cost of grinding. The PKC used by Yussof (1985) was not a product of heat treated kernels as was the case with the solvent-extracted or screw-pressed kernels in this study. The application of heat in the presence of water might have caused the Milliard reaction, which could have rendered the nitrogen unavailable to both the rumen microbes and the host animal. This could also partly explain the low intakes of PKC.

Table 1. Mean weight performance, feed and water intakes and mortality rates of Djallonké sheep.








Initial body weight (kg)






Final body weight (kg)






Changes in body weight (kg/84 days)






Daily dry matter intake of:

CP (g/kgW0.75)






PKC (g/kgW0.75)






CP and PKC (g/kgW0.75)






Daily water intake (ml/kgW0.75)






Mortality rate (%)






abc = Values in a row with different superscripts are significantly different (P<0.05).

Table 2. Mean performance characteristics of Djallonké sheep.








Initial body weight (kg)






Metabolic body weight (kgW0.75)






Daily intake of CP (g)






Daily energy intake from CP (MJ/ME)






Maintenance energy requirements (MJ ME/day)






Energy intake (from CP) as a proportion of maintenance energy requirement (x maintenance)






Rumen degradable nitrogen requirement for the level of energy intake (mg/day)






Quantity of nitrogen supplied by CP (mg/day)






Mean quantity of nitrogen contained in the PKC eaten (mg)






Deficiency of rumen degradable nitrogen (mg/day)






The zero hour dry matter degradability values for PKC and CP shown in Figure 1 may be misleading. The values seem to be high whereas the actual degradability values may not have been. This could be because the PKC was pulverised through a 3 mm sieve into very fine powder, most of which could have leaked out of the nylon bag and therefore not degraded. The filter paper soluble fraction was 17%. The calculated mean energy intakes from CP ranged from 1.24 to 1.46 x maintenance energy requirements of the animals. The calculated rumen degradable nitrogen supplied by CP in this study did not meet the calculated RDN requirement. The deficits ranged from 1969 to 2388 mg/day. These deficits in the requirements of RDN could not have been met by nitrogen supplied by the PKC at the levels of intake recorded, even if all the nitrogen it contained was rumen degradable.

Notwithstanding the deficiency of RDN, about 74% of the animals survived on the diets for three months. The intakes of the diets (59 to 68 g/kg W0.75 per day) were also remarkable. though lower than the values (87 to 108 g/kg W0.75 per day) reported by Adegbola et al (1988) when they fed CP diets containing adequate amounts of nitrogen to the same breed of sheep.


The funding of this study by the European Community (EC) is acknowledged.


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