The Relationship Between the Crude Protein Content and the Apparent Ileal Digestible Amino Acid Content of Wheat and Sorghum

Background – Provision of adequate levels of essential amino acids is very important in the compilation of diets, especially for monogastric animals. We (Ravindran and Bryden, 1999; Li et al., 2002) have found that formulating diets based on digestible amino acid values was superior to those based on total amino acids. Amino acid analysis and digestible amino acid determination are too costly and time consuming for routine investigation in the feed industry and it would be helpful if the apparent ileal digestible amino acid content of a feedstuff could be deduced from its total crude protein content, which is routinely determined. Wheat and sorghum are the major components of poultry diets and contribute a substantial proportion of dietary protein. Objective – To investigate the relationship between the total crude protein and apparent ileal digestible amino acid content of Australian wheat and sorghum. Design – Male broilers at 35 days of age were allocated to pens with 7 birds per pen. Twenty-one wheat and seven sorghum with total crude protein contents ranging from 94-172 and 80-118 g/kg (air dry basis), respectively were incorporated as the sole source of dietary protein in experimental diets. Celite, a source of acid insoluble ash, was added (20 g/kg) to all diets as an indigestible marker. Each experimental diet was fed to three pens for 5 days. At the end of trial all birds were sacrificed and the digesta from the lower portion of the ileum was collected and pooled with the contents of the other birds from the same group. Freeze-dried digesta were analysed for crude protein, amino acids and acid insoluble ash. Outcomes – There were strong and significant (