The nutritive value of full-fat and defatted Australian rice bran. V. The apparent retention of minerals and apparent digestibility of amino acids in chickens and adult cockerels fitted with ileal cannulae

Abstract

Three experiments examined the apparent retention of minerals and the digestibility of amino acids from diets based on rice bran in male growing chickens and adult cockerels. In Experiments 1 and 2, the apparent retention of calcium declined with increasing bran inclusion and in many instances with chickens values were negative. For each 1 g kg −1 addition of rice bran to the diet, there was an additional output of 0.24 and 1.45 mg calcium g −1 dietary calcium intake at the terminal ileum of cockerels and male chickens, respectively. Retention values for magnesium and phosphorus, measured with chickens and adult cockerels, were positive; although they did not change substantially with increased rice bran inclusion in the diet, these values were usually lower on diets with than without rice bran. There were few differences relating to source of bran in Experiments 1 and 2, and when examined further in Experiment 3, this was confirmed. The apparent retention of calcium was positive on each diet in Experiment 3, but retention of phosphorus was much lower on 1982 defatted rice bran (DFRB) than the basal diet or the diet containing Starbonnet full-fat rice bran (FFRB). Amino acid digestibility of rice bran was consistently lower for growing chickens (Experiment 1) than mature birds (Experiment 2). In Experiment 1, amino acid digestibility for Starbonnet FFRB was significantly better for both essential (0.69 vs. 0.52) and non-essential (0.73 vs. 0.54) amino acids than 1982 DFRB. There was a tendency for Starbonnet FFRB to be higher in amino acid digestibility for mature cockerels than the 1982 DFRB and 1982 FFRB, but not the 1981 DFRB. Digestibility of lysine was consistently above 0.85 for each bran tested with mature birds, but only 0.63 for growing chickens.