SummaryA series of five metabolism trials was made to determine apparent nitrogen digestibility and metabolizable energy (ME) contents of protein rich feedingstuffs. The mean nitrogen digestibilities of fish meal, groundnut, mustard, sesame and cottonseed cakes were 66, 69, 68, 57 and 40%, respectively. Corresponding values for metabolizable energy values were 1820, 2460, 2330, 1870 and 1530 kcal/kg, respectively. The metabolizable energy contents of coconut cake, niger cake and blood meal were 1190, 2360 and 2190 kcal/kg, respectively. The quantity of protein, its digestibility and crude fibre content in the cakes are the prime factors for this trend in MB. Simple and multiple regression equations were derived from biologically assayed metabolizable energy and chemically analysed energy-yielding nutrient contents of the feedingstuffs. The simple regression equation is:ME kcal/kg = 32·95 (% crude protein + % ether extract × 2·25+ % available carbohydrate)–29·20.The multiple regression equation is:ME kcal/kg = 370·29 + (24·47 × % crude protein)+ (65·77 × % ether extract)+ (44·07 × % available carbohydrate)- (8·15 × % crude fibre).The correlation coefficients of simple and multiple regression equations were 0·72 and 0·73, respectively, indicating that there is very little advantage for prediction in using the multiple regression equation. The usefulness of the equation for routine checking of poultry feeds for ME is apparent since the nutrients required to predict metabolizable energy can be analysed within a short period of time.

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Experiments were made to assess the nutritive value of expeller-proeessed mustard cake (MS) for egg-type and meat-type chicks. Eight samples of MS on average contained 37-2 % crude protein, 27-5 % true protein, 12-6 % available carbohydrate and 2-09 % tannins. The average metabolizable energy content (ME) of eight samples of MS for egg-type and meat-type chicks were 2350 and 2300 kcal/kg respectively. MS in the diet replacing groundnut cake (GN) which formed 30-32 % of the control diets was found to have no effect on growth rate of the chicks of either breed although there was thyroid enlargement. MS was also found not to affect the body composition of the chicks.

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