Influence of caecectomy on digestibility of amino acids by roosters fed distillers' dried grains with solubles

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Abstract
Several laboratories are currently using the rapid excreta collection assay desoribed by Sibbald (1979), or a modification thereof, to measure digestibility of amino acids (AA) in feedingstuffs for poultry. The use of faecal or excreta collection assays to measure utilization of dietary AA has been frequently questioned because of the unknown effects of gut micro-organisms on AA excretion. These effects may be large with swine (Holmes et al. 1974) and thus many researchers have used ileal digesta collection to measure AA digestibility with pigs (Zebrowska, 1978). The question on significance of microbial effects is less clear with poultry. Some studies with germ-free chicks suggested that influence of the hindgut microflora on digestibility of protein and AA was significant (Salter & Coates, 1971; Elwell & Soares, 1975), whereas others indicated that these effects were small and probably negligible (Salter, Coates & Hewitt, 1974; Salter & Fulford, 1974). More recently, Parsons, Potter, Brown, Wilkins & Bliss (1982) concluded that microbial fermentation in the hindgut may have a significant effect on AA excretion by poultry, but to a much lesser extent than swine.