EFFECTS OF PROCESSED FALSE YAM TUBER ON NUTRIENT METABOLISM AND PHYSIOLOGY OF BROILER CHICKENS

Abstract

Six separate experiments were carried out to assess the effects of anti-nutritive elements in the false yam tuber on physiology and metabolism of broiler chickens. In experiment 1, the nutrient composition of the untreated sun-dried false yam tuber was determined. It comprised on dry matter basis 5.34% crude protein, 4.35% ether extract, 2.50% Ash and 3140.81Kcal metabolizable energy/kg. Also, the mineral composition of the untreated sun-dried false yam tuber revealed the presence of potassium, magnesium, calcium, phosphorus, sodium, iron, zinc and copper. In experiment 2, phytochemical screening of the untreated sun-dried false yam tuber showed, on dry matter basis, the presence of alkaloid (1.53%), phytate (2.97%), oxalate (2.64%) and mucilage (11.25%). In Experiment 3, the effects of processing on the nutrient and antinutritive factors of the false yam tuber were determined. Processed products used were Blanched false yam (BFYM), 0.1M Sodium hydroxide treated false yam (NaTFYM), 0.1M Sodium hydroxide treated blanched false yam (NaTBFYM) and Fermented false yam (FFYM). The macro-mineral elements which were consistently and significantly higher (P < 0.05) after processing when compared to the unprocessed ones are phosphorus, calcium, potassium and the trace elements iron, zinc, copper and manganese. Generally, processing caused reduction in phytate (27.95%), alkaloids (37.25%), saponins (68.18%), terpenoids (69.57%), oxalates (84.47%) and mucilage (100%) in the fermented false yam. Experiment 4 investigated effects of prolonged fermentation on microbial content of fermented false yam product and its safety. The following microorganisms were identified in the fermented false yam product: Enterobacter coloacae, Agglumerans and Bacillus spp all of them amounting to a value of 2.48 x 107 CFU/ml. In addition the yeast and mould cell counts averaged 2.5 x 105 CFU/ml. Experiment 5 involved toxicity study using Sprague Dawley rats for a period of 90 days to determine potential toxicity of the residual anti-nutritional factors in the processed false yam products. Rats fed on the processed false yam products inclusion rates of 5, 10 and 20g/kg did not show any visible clinical signs, deaths, or toxic effect on the animals’ behaviour. Haematological values measured showed a significant (P <0.05) reduction in HGBT, HCT and RBC levels of rats fed on 20g/kg. Biochemical parameters such as ALT and AST measured for the treatment rats showed significant difference (P<0.05) from the control rats. Organs such as kidneys, spleen, lungs and liver of rats fed on the 10g/kg and the 20g/kg of the processed false yam products were significantly (P < 0.05) reduced compared with the control. Experiment 6 investigated the effect of residual anti-nutritive factors in the processed false yam products on growth, blood metabolites and carcass characteristics of broiler chickens. A total of 350 Cobb broilers at four weeks of age were fed seven experimental diets for four weeks using 2x3 factorial designs. The experimental diets comprised fermented false yam (FFYM) and 0.1MSodium hydroxide treated blanched false yam (NaBFYM) which replaced portions of the maize on weight by weight basis at inclusion levels of 0%, 5%, 10% and 15%. The control diet (0%) contained no processed false yam products. The highest daily feed intake was reported in birds fed on the fermented false yam treatment. Daily live-weight gain of birds on the treatment diets decreased as the inclusion rate increased showing significant difference (P<0.05) at 15% when compared with the control. Haematological parameters measured for birds on the processed false yam such as WBC, RBC, HB, MCHC, RDW-CV, PDW, MPV and PCT were significantly different (P<0.05) from those of the control birds. It can be concluded that fermented and 0.1M sodium hydroxide treated blanched false yam tuber can replace maize at 10% inclusion in diets with minimal residual antinutritive effect on digestibility and growth of the broiler chicken.