Utilisation of whole cassava plant in the diets of growing pigs in the tropics

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1 Livestock Research for Rural Development (13) Utilisation of whole cassava plant in the diets of growing pigs in the tropics E O Akinfala and O O Tewe* Department of Animal Science, Obafemi Awolowo University, Ile- Ife, Nigeria. * Department of Animal Science, University of Ibadan, Ibadan, Nigeria. akinfala@oauife.edu.ng Abstract The effects of inclusion of whole cassava plant (flour, peels, leaves and tender stems) as a replacement for maize in the diets of growing pigs on growth, feed intake, feed to gain ratio, serum biochemical and haematological indices were studied for eight weeks. Twenty-four pigs with initial mean weight of 12.5±0.32kg were used. Three diets were formulated. M: which was maize based served as control. 40C: contained 40% cassava products (20% flour, 10% peels and 10% leaves plus tender stems). C60: contained 60% cassava products (40% flour, 10% peels and 10% leaves plus tender stems). The ratio of leaves to tender stems was 3:1. All the diets were made to be isonitrogenous at 3.0 % N and isocaloric at 2.9 kcal/g DE. The weight gained ranged from 384 to 411 g/day with no differences among diets. The values obtained for serum metabolites were similar on all diets. The thiocyanate value of the blood ranged from 0.57 to 0.66 mg/100ml with highest value occurring in diet C60.

2 The inclusion of dried whole cassava plant at levels of up to 60% in the diets of growing pigs had no adverse effect on their performance, serum and haematological indices. Key words: Pigs, cassava, whole plant, growth, metabolic profile Introduction The extremely high prices of conventional feed ingredients in Nigeria has increased the feeding cost to about 60-80% of the total cost of intensive livestock production especially for poultry and pigs. (Fajimi et al 1975; Tewe 1997). Several researchers (Job 1975; Tewe 1982; Iyayi and 1994) have confirmed the suitability of cassava for pig feeding, and the potential of cassava meal as good substitute for maize meal for all classes of pigs. However, there is paucity of information on the use of whole cassava plant (flour, peels, leaves and tender stems) for pig feeding because earlier research efforts have been on either the use of flour or peels or leaves to feed pigs. The increasing pressure on the use of cereals by human population and livestock feed millers, coupled with a deficit in animal protein intake especially in developing countries necessitate the use of unconventional feedstuffs for livestock production especially pigs. The considerable information, which has been accumulated on the positive effects of cassava meals as feed ingredients for pigs stimulated the current investigation. For instance, cassava flour and peels could serve as source of energy because the nitrogen free extract is high and can compare favourably with that of maize. The crude protein value of leaves plus tender stem is high about 23%. It is rich in vitamins and the amino acids profile can compare favourably with that of soya bean meal (Khajarern et al 1977). The leaf is high in lysine but low in sulphur

3 containing amino acids such as methionine and cystine (Devendra 1977). Cassava peels, leaves and tender stem are under utilized in Nigeria because they are left to rot away on farms and homesteads after harvesting. Hence, the objective of the present study was to furnish information on the effect of inclusion of whole cassava plant in the diet of growing pigs on their growth, feed intake, feed to gain ratio, serum metabolites and haematological indices. The use of the whole cassava plant could go a long way in reducing costs of production, in alleviating the problem of direct competition by nonruminants with people for feedstuffs like maize and possibly the evolution of a sustainable crop-livestock farming system in Nigeria. Materials and methods Three diets were formulated to be isonitrogenous (3 % N) and isocaloric (2.9 kcal/g Digestible energy). Diet M was maize based, diet C40 ontained 40% dried cassava products (20% flour, 10% peels and 10% leaves plus tender stem) and diet C60 contained 60% dried cassava products (40% flour, 10% peels and 10% leaves plus tender stems). The ratio of cassava leaves to tender stems was 3:1. The cassava flour, peels, leaves and tender stems were harvested from the neighbouring farms around University of Ibadan Teaching and Research Farm. The leaves and tender stems were obtained from harvested cassava. The cassava tubers were peeled and the tuber chopped into bits. The tubers, peels, leaves and tender stems were sun-dried for about 5-10 days depending on the intensity of sunlight to about 10% moisture content. They were later taken for milling, All other ingredients were got from a feed ingredients depot near University of Ibadan (Table 1).

4 Table 1: Composition of experimental diets Ingredients, % Diets M C40 C60 Maize Maize offal Cassava flour Cassava peel Cassava leaves + Tender stems Palm kernel cake Groundnut cake Fish meal Blood meal Oyster shell Bone meal *Premix (Vit/Min) Salt Total *Premix supplied per kg diet 4,000,000 I.U Vit.A, 800,000 I.U Vit. D3, 12,000 I.U Vit E, 0.80g Vit K, 0.60g Vit B1, 2.0g Vit B2, 1.40g pantothenic acid, 20.00mg biotin, 0.40g folic acid, 120.0g cholinechloride, 8.0g zinc bacitracin, 40.0g manganese, 20.0g iron, 18.0g zinc, 0.80g copper, 0.60g iodine, 0.09g cobalt, 0.04g

5 selenium, 36.0g lasalocid (Avatec). Twenty-four weaner pigs with initial mean body weight of 12.5±0.32kg (Crosses of Large White x Hampshire) were assigned randomly to the three dietary treatments. The experiment was conducted for eight weeks. The animals were fed twice daily at 09:00a.m and 02:00p.m. They were fed at 3 to 5% of their body weight. Water was supplied to the animals ad libitum. The animals were housed individually in concrete floored pens equipped with watering and feeding facilities. Routine management practices were followed. Records of feed consumption, and weight gained each week were kept on a treatment basis. Blood samples were collected from the animals after fasting overnight after eight weeks of observation. The blood samples were collected from individual animal with the aid of sterilised 10-gauge needles made through the anterior Vena Cava. The bleeding was done in the morning before feeding. Ethylenediamine tetra acetic acid (EDTA) an anti coagulant was added to the test tubes meant for haematological indices. Haematological measurements were determined using methods outlined by Kelly (1979). The blood samples in the tubes meant for biochemical assays were allowed to clot before centrifuging to obtain serum used in the determination of some serum metabolites using standard chemical procedures: urea (Harrison 1947), creatinine (Bioness and Tausky 1945), serum protein Buriet method (Reinhold 1953), albumin (Donmas et al 1971), glucose and cholesterol. Samples of the diets were dried in a force-draught oven at 60 o C for 24h and ground in a laboratory hammer mill before proximate analysis (AOAC 1990). The cyanide of the diets was analysed using the method outlined by ISO (1975). Table 2: Proximate composition, digestible energy and cyanide

6 level of experimental diets Parameters Diets M C40 C60 Dry matter basis Crude protein, % Crude fibre, % Ether extract, % Ash, % Nitrogen free extract, % *Digestible energy DE, Kcal/g HCN, mg/kg ND* *ND = Not determined. *Digestible energy calculated using the prediction equation of Morgan et al 1975 The data were subjected to statistical analysis using SAS computer software package (1988). Results and discussion The growth rate, feed intake and feed conversion parameters were not significantly influenced (P>0.05) by the dietary treatments (Table 3). Table 3: Performance of pigs fed experimental diets M C40 C60 Feed intake, kg DM/day Weight gain, kg/day 0.411± ± ±0.02 Feed:gain ratio 2.17 ± ± ±0.65

7 There were significant (P>0.05) differences only in serum tryglyceride and thiocyanate levels (table 4). There was no apparent relationship between serum tryglyceride values and the dietary treatments. Thiocyanate levels appeared to reflect levels of cassava products in the feed but were within accepted levels for this metabolite. Table 4: Serum metabolites of growing pigs fed experimental diets M C40 C60 Total protein, g/100ml 6.10 ± ± ±0.08 Albumin, g/100ml 2.70 ± ± ±0.08 Globulin, g/100ml 3.40 ± ± ±0.17 Albumin-Globulin ratio 0.80 ± ± ±0.11 Creatinine, mg/100ml 1.05 ± ± ±0.08 Urea, mg/100ml 18.0 ± ± ±1.63 Cholesterol, mg/100ml 181± ± ±2.04 Glucose, mg/100ml 71.0± ± ±1.23 Triglyceride, mg/100ml 80.0 a ± a ± b ±0.82 Serum thiocyanate, mg/100ml 0.57 c ± b ± a ±0.01 abc: Means along the same row having different superscripts differ significantly at P<0.05 Table 5: Haematological indices of growing pigs fed experimental diets M C40 C60 Packed cell volume (PCV), % 41.0 a ± b ± b ±0.41 Red blood cell (RBC) x 10-6 /µl 7.5 a ± b ± b ±0.12 Haemoglobin (Hb), g/100ml 12.7 a ± b ± b ±0.12 White blood cell (WBC), x10-3 /µl 20,200 a ±1,388 21,350 a ±775 9,000 a ±2,122 a, b, c: Means along the same row having different superscript differ significantly at P<0.05. The serum metabolites (albumin, globulin, creatinine and urea) are indicators of adequacy of protein in terms of quality and quantity in the diet. These parameters show whether there are protein malnutrition, alterations in the dietary intake of protein and pattern of utilization, and possibly the extent of muscle wastage and subsequent degradation of muscle phosphorous creatinine to form creatinine (Eggum 1970). Though cyanide which is found mainly in cassava may affect the pattern of protein utilization in animals (Iyayi and Tewe 1992), the evidence was not pronounced in this study because, the values obtained for serum metabolites fall within the range recommended by Mistrukan and Rawnsley (1977) and Adesehinwa (1997) for normal growing pigs. Other serum metabolites (glucose, triglyceride and cholesterol) that indicate the

8 efficiency of utilisation of metabolisable energy in a given diet (Fanimo 1991 and Anderson 1983) were similar in all the treatments. Haematological indices provide an opportunity to clinically investigate the presence of several metabolites and other constituents in the body of animals. They are good ways of assessing the health status of an animal and play a vital role in the physiological, nutritional and pathological status of an organism by distinguishing normal state from state of stress, which can be nutritional, environmental or physical (Tewe et al 1981; Church et al 1984 ; Onifade 1993). Cyanide has great affinity for metals such as copper and iron, making them unavailable, thereby reducing the haemoglobin count and effective transportation of oxygen and carbohydrate. Cyanide also causes reduction in growth rate by inhibiting the intra-thyroidal uptake of iodine, causing an increase in secretion of thyroid stimulating hormone (TSH) and thereby causing a reduction in thyroxin level which is necessary for growth (Tewe 1991). The haematological results showed higher values for pigs on the control diet (maize based) (P<0.05) compared to the cassavabased diets. However, all the values obtained were within the range recommended for healthy pigs by Dukes (1974) and Schalm et al (1975). The total white blood cell (WBC) counts obtained in the study were within the range recommended. Conclusions The inclusion of the dried whole cassava plant (peels, leaves plus tender stems and flour) at up to 60% in the diets of growing pigs did not affect the performance and serum metabolites.

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