MAINTENANCE OF THE BIOLOGICAL EFFICACY IN CHICKS OF A CECAL COMPETITIVE-EXCLUSION CULTURE AGAINST SALMONELLA BY CONTINUOUS-FLOW FERMENTATION

A competitive-exclusion culture was isolated by the continuous-flow cu lture 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 degrees C were provided to da y-old chicks. Experiments utilizing the original culture were performe d after 5, 30, 100, and 365 days of continuous-flow conditions and the lyophilized culture after 5 days of continuous-flow culture. In all e xperiments chicks were challenged with 10(4) CFU of Salmonella typhimu rium at 3 days of age. At 10 days of age the chicks were killed and ce cal contents analyzed for fermentation parameters and for S. typhumuri um 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) compa red to untreated controls in all experiments. The results indicate tha t continuous-flow cultures can be used as a practical method to mainta in competetive-exclusion cultures without loss of efficacy, and contin uous-flow cultures stored in a lyophilized form can be reconstituted a nd still maintain efficacy.