Nutritional value of yeast (Saccharomyces cerevisiae   ) and its derived products, extract and cell wall, in poultry feeding.

To assess the nutritional value for poultry of brewer's yeast (Y) (Saccharomyces cerevisiae ), and that of its derived products: extract (E) and cell wall (CW), after being submitted to a process of autolysis, a balance trial was conducted with 48 adult, cecectomized roosters of the Gold Line strain. True digestibility of dry matter (DMTD), of nitrogen corrected for uric acid (NuTD), and of amino acids (AATD); and true metabolizable energy corrected to zero nitrogen balance (TMEn) were determined. Total nitrogen content in Y, E and CW analyzed 8.4, 11.3, and 3.5 %, respectively. Balance trial results showed highly significant differences among the three feedstuffs evaluated, in favor of E, in almost all the criteria of evaluation. Mean values of Y, E, and CW for DMTD (%) were 45.7 ± 0.8, 59.7 ± 0.8, and 25.0 ± 1.1, respectively; those of Y and E were, for AATD (%), 75.,4 and 91.6; and for methionine digestibility (%), 86.2 and 98.9; but for cysteine digestibility (%), 67.3 and 63.2. Autolysis of the yeast increased the concentration of nutrients, in the extract and favored digestibilities of dry matter; total nitrogen; and aminoacids, except cysteine; it also increased the metabolizable energy value