Microbial Contribution to Dry Matter and Amino Acid Content of Poultry Excreta

A physical separation procedure was developed for determination of the microbial contribution to dry matter and amino acid content of excreta from adult Single Comb White Leghorn roosters. The procedure included repeated mixing of excreta in saline, filtration, and low-speed and high-speed centrifugation. Excreta were separated into microbial, insoluble, and soluble fractions. Total facultative and direct microscopic counts of bacteria in the fractions indicated that 90% of the measured microbial cells were in the microbial fraction. Purity of the microbial fraction was ascertained by comparison of its amino acid composition to that of isolated microbial cells from poultry excreta. The microbial contribution to dry matter and amino acid content of poultry excreta was estimated to be 11 and 25%, respectively. The results indicate that bacteria represent a substantial proportion of amino acids in poultry excreta. Thus, measurement of amino acid digestibility with fecal collection methods may not be valid.