Individual and Combined Effects of a Direct-Fed Microbial and Calcium Butyrate on Growth Performance, Intestinal Histology and Gut Microbiota of Broiler Chickens

This study evaluated the effects of a Bacillus direct-fed microbial and microencapsulated calcium butyrate fed individually and in combination, as compared to an antibiotic growth promoter, on growth performance, processing characteristics, intestinal morphology, and intestinal microbiota of Ross 708 broilers reared from 0 to 47 d post-hatch. Dietary treatments included: (1) a negative control with no antimicrobial (NC), (2) a positive control diet containing bacitracin methylene disalicylate (PC), (3) a diet containing a Bacillus direct-fed microbial (CS), (4) a diet containing microencapsulated calcium butyrate (BP), and (5) a diet containing both CS and BP. Treatments were replicated with 10 pens of 20 birds each. From 0 to 15 d post-hatch, the FCR of broilers fed the PC, CS, BP, and CS + BP diets were lower (p < 0.05) than those fed the NC diet, but treatment effects (p > 0.05) were not observed on subsequent performance. BP supplementation improved (p < 0.05) total breast meat weight and yield at processing. Intestinal histology was not influenced (p > 0.05) by the treatment. Analysis of the jejunal microbiota collected at 15 d post-hatch revealed that the genus SMB53 was significantly lower for the CS group, and Sporanaerobacter was lower in the CS and CS + BP groups compared with the NC (p < 0.05). The jejunal microbiota from broilers in the CS + BP group had higher (p < 0.05) alpha and beta diversities compared with broilers fed the NC and CS diets. The results reflected synergistic effects between CS and BP in modulating the jejunal microbiota at 15 d that may have been related to enhanced feed efficiency (i.e., lower FCR) observed during this period.