Effect of mixed cecal microflora maintained in continuous culture and of dietary lactose on Salmonella typhimurium colonization in broiler chicks.

Mixed cecal microflora obtained from a mature chicken were maintained in vitro in continuous-flow (CF) culture. The effect of the CF culture and dietary lactose on Salmonella typhimurium cecal colonization in broiler chicks was evaluated. When averaged across four replicates, chicks treated with the culture alone (1.75 log10 decrease) or with 5% dietary lactose alone (2.98 log10 decrease) were protected against S. typhimurium. Optimum protection against S. typhimurium was observed when birds were treated with the culture in combination with dietary lactose (4.27 log10 decrease). Dietary lactose resulted in reduced cecal pH. A large increase in cecal propionic acid was observed in the birds given the CF culture. A significant correlation (P < 0.001) was observed between the cecal concentration of undissociated propionic acid and protection against S. typhimurium colonization (r = -0.78). The results indicated that indigenous cecal flora that protect against Salmonella colonization can be maintained without loss of efficacy in CF culture.