INFLUENCE OF CAECECTOMY AND DIETARY-PROTEIN CONCENTRATION ON APPARENTEXCRETA AMINO-ACID DIGESTIBILITY IN ADULT COCKERELS

1. The influence of caecectomy and dietary crude protein content (50, 100, 150, 200 and 250 g/kg diet) on the apparent excreta amino acid di gestibilities in adult cockerels fed on semi-purified diets containing soybean meal (SBM) or cottonseed meal (CSM) as the sole source of pro tein was investigated, 2. Caecectomy had no influence on the apparent digestibilities of most amino acids in SBM, the exceptions being histi dine, arginine and lysine, but lowered the apparent digestibility of a mino acids in CSM. 3. The protein content in assay diets has a strong influence on the apparent amino acid digestibility values for poultry. Apparent values are lower when the dietary protein content is low. 4. The use of a single endogenous amino acid output value, generated by regression analysis or protein-free diets, for true digestibility adju stments across a wide range of protein intakes is questioned. In parti cular, such an application will penalise estimates of apparent digesti bility when the dietary protein content is high.