In vitro 14C-amino acid fermentation by CF3, a characterized continuous-flow competitive exclusion culture of caecal bacteria.

Competition for growth-limiting nutrients by broiler caecal bacteria and Salmonella has been suggested as one factor associated with decreased Salmonella caecal colonization. The amino acids arginine, aspartic acid, serine and threonine have been indicated as Salmonella growth-limiting nutrients. Broiler caecal bacteria maintained in a continuous-flow culture (CF3) were used as inoculum for media containing 14C-arginine, 14C-aspartic acid, 14C-serine or 14C-threonine. The 14C-labelled amino acids, except 14C-arginine, were metabolized to lactic, formic, acetic, propionic and butyric acids. In glucose-based media, 72%, 72% and 33% of the radiolabel from aspartic acid, serine and threonine, respectively, were detected in organic acids. Fermentation without glucose resulted in 48%, 50% and 71% of the radiolabel from aspartic acid, serine and threonine, respectively, being detected in organic acids. Results indicated that the early establishment of CF3 in young chicks may result in the depletion of growth-limiting amino acids and, therefore, reduction of Salmonella colonization.