The objective of the study was to determine to what extent B. subtilis DSM 32315 (BS) probiotic can ameliorate the negative effect of weaning stress on intestinal microbial profile and integrity, and growth performance, in piglets fed low or high crude protein (CP) diets. Seventy-two piglets (initial weight 7.61 ± 0.55 kg) were allotted to 4 diets in a randomized complete block design in a 2 × 2 factorial arrangement. Two protein levels included high CP (HCP; 0–14d, 20.5%; 15–42d, 19.5%) and low CP (LCP; 0–14d, 18%; 15–42d, 17%), and 2 added levels of BS included at 0 or 500 mg/kg diet. Results indicated that supplementation of BS increased (P < 0.05) Bacillus and Bifidobacterium in the ileum while there was a tendency (P = 0.057) for Lactobacillus counts regardless of CP level. However, in the colon, Bacillus and Bifidobacterium abundance was higher (P < 0.05) in LCP diets. In jejunum, supplementation of BS increased (P < 0.05) villus height (VH) in LCP diets, but this was not observed in HP diets (CP × BS interaction; P < 0.01), and villus height:crypt depth ratio (VH:CD) was increased (P < 0.01) by BS supplementation. Supplementation of BS increased (P < 0.05) VH and VH:CD only in LCP diets (CP × BS interaction; P < 0.05) in the ileum. In ileum, the relative mRNA expression of Occludin-1, and EGF and IGF-1R, increased (P < 0.05) when BS was added to LCP diets than to HCP diets (CP × BS interaction; P < 0.05). Supplementation of BS increased (P < 0.05) the apparent total-tract digestibility (ATTD) of dry matter and gross energy regardless of CP level. Furthermore, feeding BS increased daily gain (P = 0.02) and reduced feed conversion ratio (P < 0.01). In conclusion, Bacillus subtilis DSM 32315 modified hindgut bacterial composition and maintained intestinal integrity of piglets, with more pronounced benefits in piglets fed low protein diets.
Key Words: Bacillus subtilis DSM32315, gut health, low protein diet, microbiota profile, piglets