The Metabolizable Energy of Some Tropical Tuber Meals for Chicks

Abstract

Two consective experiments were conducted with 360 White Leghorn cockerels, approximately two weeks old, to compare the metabolizable energy (M.E.) and metabolizable energy corrected to nitrogen equilibrium (M.E.n) for dehydrated cassava, cocoyam, yam, plantain and sweet potato meals. These were tested at 40 and 25% levels of substitution in the first and second experiment respectively. No consistent differences were observed for the M.E. and M.E.n values due to level of substitution. The range of M.E. and M.E.n for sweet potato in both experiments (3.94–4.11 and 3.73–3.89 kcal./g.) were non-significantly higher than those for cassava (3.78–3.88 and 3.66–3.78 kcal./g.), but both these sources had significantly superior M.E. and M.E.n compared with those for yam (3.24–3.36 and 3.19–3.28 kcal./g.) and plantain (3.16–3.29 and 3.04–3.22 kcal./g.). The corresponding values of 2.73–2.88 and 2.72–2.82 kcal./g. for cocoyam were significantly (P < 0.05) lower than for all the other tubers. The percentage gross energy as M.E. for cocoyam, yam and cassava were 65.31–68.90, 75.70–78.51 and 69.60–72.42, respectively. These were significantly (P < 0.05) lower than the fairly similar values of 86.90–89.20 and 87.17–90.93 for cassava and sweet potato, respectively. Rate and efficiency of gain was best for sweet potato at both the 25 and 40% levels of substitution, cassava and plantain showing significantly lower rate and efficiency of gain in comparison. Yam in turn gave rates and efficiency of gain significantly lower than for the later two tubers while cocoyam had significantly (P < 0.05) the lowest rate and efficiency of gain. The results suggest that sweet potato and cassava are superior energy sources compared to the others, although the growth promoting ability of the cassava diet tended to be reduced by the possible presence of some residual growth inhibitory factor in the dehydrated meal.