Probiotics offer one alternative to antibiotic growth promoters as they have been shown to improve the development and maintenance of a stable gut microbiome in poultry, which leads to reduced enteric disease and improved growth performance. Therefore, the objective of this study was to delineate the effects of Bacillus subtilis DSM 32315 (BS DSM32315) on intestinal morphology, microbial composition and performance in broiler chickens. A total of 240 Arbor Acre (AA) male birds were randomly assigned to 2 dietary treatments with 10 pens of 12 birds per pen. The dietary treatments included a basal diet (Control), a basal diet supplemented with 500g/MT of BS DSM32315, 1.0x106 CFU/g feed). Corn-soybean meal based basal diets were formulated on the recommendation which is normally used in china for starter (day 1-14), grower (day 15-28) and finisher (day 29-42) phases. Water and pelleted feed were provided ad libitum. Supplemental BS DSM32315 significantly increased (P<0.05) body weight, average daily gain, and feed intake of broilers at 28 and 42 d of age. Intestinal lesion scores were significantly reduced (P<0.05) in birds fed BS DSM32315, while there was tendency for higher (P=0.077) expression of Ileal tumor necrosis factor (TNF)-α. In the cecum, PCA plot defined groups from control and treatment groups occupied distinct positions. Birds supplemented with BS DSM32315 had higher abundance of Firmicutes and lower abundance of Bacteroidetes which also increased the abundances of Christensenellaceae and Caulobacteraceae, and simultaneously reduced the abundances of potentially harmful bacteria such as Vampirovibrio, Escherichia/Shigella and Parabacteroides. The villus height (VH) and VH to crypt depth ratio of ileum was significantly higher (P<0.05) in treatment group relative to control. Clostridiales and Bacteroidales accounted for the largest proportion in the community, which were respectively increased and decreased in treatment group as compared to control. Within Clostridiales, the majority belonged to the Ruminococcaceae and Lachnospiraceae families. Functional comparison based on KEGG orthologue groups demonstrated a decreasing trend (P<0.10) in the enrichment of the pathways for enzyme families, metabolism of cofactors and vitamins in birds fed BS DSM32315. Overall, supplementation of supplemental B. subtilis DSM 32315 altered microbial composition and intestinal morphology, thus improving the growth performance.
Keywords: Bacillus subtilis DSM32315, intestinal morphology, gut microbiome, performance.