DEVELOPMENT OF AN ILEAL AMINO-ACID DIGESTIBILITY ASSAY FOR THE GROWING CHICKEN - EFFECTS OF TIME AFTER FEEDING AND SITE OF SAMPLING

1. The study aimed to establish the optimum time after ingestion and o ptimum sampling site for the development of an ileal amino acid digest ibility assay for broiler chickens. 2. To establish the optimal sampli ng time, 4-week-old broiler chickens were given one of 6 protein sourc es (meat-and-bone, soyabean, cottonseed, fish, maize and wheat meals) as the sole source of protein in a test diet. The diets contained chro mic oxide as an indigestible marker. The birds were starved for 24 h, fed and subsequently killed for sampling of ileal digesta (terminal 15 cm) at 2, 3, 4, 5 and 6 h after the start of feeding. 3. For the soya bean, fish, wheat and maize meal diets, sampling time had no significa nt effect on apparent ileal nitrogen digestibility, whereas for the me at-and-bone and cottonseed meal diets there was a significant quadrati c effect of sampling time. The amount of digesta collected was maximis ed and the mean apparent ileal nitrogen digestibility had the lowest v ariation around the 4 h sampling time. 4. To establish the optimum sam pling site, 4-week-old chickens were given either a meat-and-bone, a s oyabean or a wheat bran meal-based diet. The birds were killed 4 h aft er the start of feeding and digesta were sampled from 0-10, 0-15, 0-20 or 0-25 cm of terminal ileum. 5. There was no significant effect of s ampling site on the apparent ileal digestibility of dietary nitrogen. The terminal 15 cm of ileum was considered a preferred site for sampli ng ileal digesta from broiler chickens.