Bioefficacy of a probiotic feed additive in broiler diets.

Three experiments were conducted to evaluate the effects of a probiotic supplement on the performance of broiler chickens. In each experiment, two treatments were applied during both the starter (1-21d) and the grower (22-42d) phases: a basal diet, and the basal diet supplemented with 10 CFU/kg Enterococcus faecium CECT 4515. Diets were presented as mash (Experiments I and II) or pellets (Experiment III) following local custom, and were based on wheat, barley, maize and soybean meal. 18, 12 and 16 replicates of 22, 60 and 40 Ross-308 birds per treatment were used in Experiments I, II and III, respectively. In all the Experiments, probiotic supplementation increased feed intake at 21 d (53.3 vs 55.3 g/d; 46.4 vs 47.9 g/d; 41.0 vs 46.8 g/d; P<0.050). In addition, probiotic supplementation also increased growth in Experiments I and III (36.3 vs 37.8 g/d; 26.6 vs 30.1 g/d; P<0.050), and in Experiment II (28.0 vs 28.7 g/d; P<0.100). Over the whole period, significant differences were also observed for growth and feed intake in Experiment III, but only for feed intake in Experiment I, and were absent in Experiment II. These results suggest that the probiotic tested improves the performance of birds especially between 1 and 21 d.