Maintenance of the Biological Efficacy in Chicks of a Cecal Competitive-Exclusion Culture against Salmonella by...

A competitive-exclusion culture was isolated by the continuous-flow culture of chicken cecal bacteria. The original continuous-flow culture and a continuous-flow culture derived from a lyophilized sample of it that had been stored for 180 days at -70°C were provided to day-old chicks. Experiments utilizing the original culture were performed after 5, 30, 100, and 365 days of continuous-flow conditions and the lyophilized culture after 5 days of continuous-flow culture. In all experiments chicks were challenged with 10⁴ CFU of Salmonella typhimurium at 3 days of age. At 10 days of age the chicks were killed and cecal contents analyzed for fermentation parameters and for S. typhumurium colonization. Ten-day-old chicks provided with the original or the lyophilized culture had significantly increased cecal propionic acid (P < 0.05) and decreased Salmonella cecal colonization (P < 0.05) compared to untreated controls in all experiments. The results indicate that continuous-flow cultures can be used as a practical method to maintain competetive-exclusion cultures without loss of efficacy, and continuous-flow cultures stored in a lyophilized form can be reconstituted and still maintain efficacy.