Effects of dietary supplementation with Bacillus subtilis LS 1-2 fermentation biomass on growth performance, nutrient digestibility, cecal microbiota and intestinal morphology of weanling pig

The present study investigated the effects of dietary supplementation with Bacillus subtilis LS 1-2 and citrus-juice waste fermentation biomass (BS 1-2 fermentation biomass) on growth performance, coefficient of total tract apparent digestibility (CTTAD) of nutrients, serum immunoglobulins, cecal microbiota and intestinal morphology of weanling pigs. A total of 240 weaned pigs (Landrace × Yorkshire × Duroc, initial body weight (BW): 6.4 ± 0.5 kg; 21 days of age) were randomly allotted to 4 treatments on the basis of BW (4 pens per treatment with 15 pigs in each pen). The dietary treatments included a basal diet supplemented with 0 (control), 1.5, 3.0 or 4.5 g/kg BS 1-2 fermentation biomass. The experimental diets were fed in a meal form for 2 phases (days 0-14, phase I and days 14-28, phase II). Pigs fed increasing dietary concentrations of BS 1-2 fermentation biomass had linear improvement (P<0.05) in overall average daily gain (ADG), average daily feed intake (ADFI), gain:feed (G:F) and CTTAD of dry matter (DM), gross energy (GE) and crude protein (CP). Also, overall ADG and ADFI of pigs fed 3.0 and 4.5 g/kg diets BS 1-2 fermentation biomass were greater (P<0.05) than pigs fed the control diet; whereas, G:F and CTTAD of DM, GE and CP of pigs fed 4.5 g/kg diet BS 1-2 fermentation biomass were greater (P<0.05) than pigs fed the control diet. At days 14 and 28, dietary increasing levels of BS 1-2 fermentation biomass linearly increased (P<0.05) serum IgG and IgA concentrations. At days 28, pigs fed increasing dietary concentrations of BS 1-2 fermentation biomass had fewer (linear, P<0.05) cecal Clostridium spp. and coliforms. Moreover, pigs fed the 4.5 g/kg diet BS 1-2 fermentation biomass had fewer (P<0.05) cecal Clostridium spp. and coliforms than pigs fed the control diet. On day 28, there was a significant linear effect of treatment on the villus height and villus height:crypt depth (VH:CD) of the duodenum, jejunum and ileum of pigs. Pigs fed the diet supplemented with 4.5 g/kg BS 1-2 fermentation biomass had greater (P<0.05) villus height and VH:CD (duodenum, jejunum and ileum) than those fed the control diet. The results suggest that BS 1-2 fermentation biomass had beneficial effects on weanling pigs growth performance, CTTAD of nutrients, cecal microbiota, serum immunoglobulins and intestinal morphology. Additionally, citrus-juice waste can be used as a substrate for growth of probiotic B. subtilis LS 1-2 under solid substrate fermentation.