Probiotics: Challenging the Traditional Modes of Action

A trial was conducted to evaluate the performance of broiler birds which supplemented with a commercial inactivated probiotic. Four hundred and fifty day old broiler chickens were allocated into 3 treatments with 6 replicates each. Each replicate was placed on clean wood shavings in floor pens receiving feed and water ad libitum. In treatment 1, feed was supplemented with 500 g/ton of a heat-inactivated probiotic containing Lactobacillus spp, Bifidobacterium animalis, Pediococus acidilactici and Enterococcus faecium. In treat-ment 2, the feed was supplemented with 500 g/ton of the same probiotic without the heat-inactivating proc-ess (commercial product). In Treatment 3 the feed was supplemented with Zinc Bacitracin at 100 ppm. Dur-ing the length of the experiment the birds received the following diets: pre-initial 1 to 7 days; initial 8 to 21 days; growth, 22 to 35 days; and finisher, 36 to 40 days. Data were analyzed following the same dietary periods. In addition, data was arranged in two periods of similar length; from 1 to 21 days and from 22 to 40 days. During the pre-initial phase, treatment 2 had higher weight gain compared to treatment 1. During the initial phase, treatments 1 and 2 had lower feed conversion compared to treatment 3. In the finisher, treatments 1 and 2 had higher body weight and lower feed conversion than treatment 3. In conclusion, regu-lar and inactivated probiotics had a similar performance which under the conditions of this trial were supe-rior to the treatment containing 100 ppm of zinc bacitracin. These data suggest that not all growth promot-ing effects are mediated by bacterial metabolites or active colonization of the gastrointestinal tract.