Supplemental Probiotics, Postbiotics, and Their Combination on the Growth, Slaughter Variables, Organ Development, Intestinal Morphology, and Cecal Microbiota of Broilers.

This study was performed to evaluate the effects of dietary supplementation with viable Bacillus subtilis, inactivated Lactobacillus plantarum, and their combination on growth and slaughter performance, immune organ and small intestine development, and cecal microbiota of broilers. A total of 480 one-day-old broilers were used across a 42-day feeding experiment and were fed a basal diet, a basal diet + 300 mg/kg viable B. subtilis (probiotic), 320 mg/kg heat-killed L. plantarum (postbiotic), or their mixtures (combination). Each diet had six replicates, and each replicate had 20 broilers. Compared to the control group, the final body weight and average daily gain increased, and the feed conversion ratio decreased in the probiotic and postbiotic groups, while the combination group showed parameters comparable to those of the postbiotic group. Feeding broilers with probiotic, postbiotic, and their combination increased the dressing-out percentage, indices of the spleen and bursa of Fabricius, and lengths and weights of the small intestine. In addition, the villus height/crypt depth ratio of both the duodenum and jejunum was increased in the probiotic and postbiotic groups. Broilers in the combination group had a lower abundance of Proteobacteria, while those in the probiotic and postbiotic groups had a higher abundance of Desulfovibrio in the cecum. Overall, we concluded that dietary supplementation with viable B. subtilis and inactivated L. plantarum could improve growth and slaughter performance, organ development, intestinal morphology, and cecal microbiota of broilers. However, their combination had not yielded a synergistic and additive effect on broilers.