Ileal endogenous amino acid losses: Response of broiler chickens to fiber and mild coccidial vaccine challenge

Abstract The effects of mild coccidial vaccine (5× dose) challenge and fiber levels on ileal endogenous amino acid (EAA) losses was determined in 26-d-old broiler chickens using the regression method. Birds were fed semipurified diets containing 3 levels of casein (40, 80, or 120 g/kg of diet) as the only source of dietary protein at 2 levels of fiber (purified cellulose at 25 or 75 g/kg of diet). One half of the experimental birds were gavaged with coccidial vaccine on d 20. The 3 levels of casein were used to determine EAA losses for each replicate cage of birds. The design of the study was a randomized complete block employing a factorial arrangement of treatments with 2 levels of coccidial challenge (control or unchallenged, and challenged) and 2 levels of fiber, with 6 replicate cages per treatment and 8 birds per cage. Birds were killed on d 26 and contents from the entire ileum were flushed with distilled water and stored at −20°C until processed. Ileal EAA losses were determined from the ordinate intercept, at zero amino acid (AA) intake, of the regression of ileal digesta AA concentration in milligrams per kilogram of DM intake against dietary AA intake in milligrams per kilogram of DM. The effect of fiber level on EAA losses, expressed in milligrams per kilogram of DM intake, were higher (P