Determination of ileal digestibility of amino acids in raw materials for broiler chickens – Results of collaborative studies and assay recommendations

Abstract Interest in amino acid digestibility of feed ingredients for poultry has been keen during the past decade. It is now acknowledged that digestibility determined at the terminal ileum is a better measure of amino acid absorption by the poultry. There had been a proliferation of publications on ileal amino acid digestibility values of range of feed ingredients, but wide variations seen in the published values remain a major concern to the end-users. In addition to the inherent ingredient variation, differences in assay methodology employed in laboratories are important contributing factors, highlighting the need for a consensus standard methodology to determine ileal amino acid digestibility. Two collaborative studies, involving five research stations, were initiated with this aim. In Study 1, maize and rapeseed meal were assayed, and pronounced variations in the ileal amino acid digestibility of these two ingredients were observed when the assay was conducted using station protocols, which differed in assay procedures. Use of a common agreed protocol in Study 2, in which a maize-soybean meal diet was assayed, completely eliminated the variation among research stations in apparent amino acid digestibility estimates. Based on these results, a consensus assay procedure for the determination of apparent ileal amino acid digestibility in feed ingredients for growing birds is proposed. It is hoped that this exercise will enable better comparison of data generated across research stations.