Amino acid digestibility of various feedstuffs using different methods

The protein requirement for poultry is actually a requirement for amino acids. Recently, there has been much interest in formulating diets on a digestible amino acid basis. The most accepted methods of determining amino acid digestibility are the precision-fed cecectomized rooster assay (PFR) and standardized ileal chick assay (SID). The PFR involves tube-feeding cecectomized adult roosters and excreta are then quantitatively collected for amino acids. For the SID, 3-week-old broiler chicks are ad libitum fed a semi-purified diet with the test ingredient added as a sole source of protein for a period of several days. The animals are then euthanized and ileal digesta are collected and analyzed for amino acids. When these two methods were compared for 15 feed ingredients, standardized amino acid digestibility was found to vary among feed ingredients and among samples of the same ingredient. There were generally no differences in amino acid digestibility for six corn and four distiller???s dried grains with solubles (DDGS) samples between the two methods. The PFR did yield significantly (P