Effect of Bacillus subtilis and Bacillus licheniformis supplementation in diets with low- and high-protein content on ileal crude protein and amino acid digestibility and intestinal microbiota composition of growing pigs
The study was performed to investigate the effect of combinations of feed additives consisting of either a combination of a probiotic and a prebiotic (synbiotic), or a combination of a probiotic and xylanase on ileal nutrient digestibility, ileal microbial metabolite concentrations, and microbial composition in ileal digesta of weaned piglets. In total, 12 six-week old barrows with an average initial body weight of 7.5 kg, fitted with an ileal T-cannula, were assigned to 3 dietary treatments. The basal diet was supplemented with a combination of 1 g probiotics (Pediococcus acidilactici, Bactocell®) and 20 g prebiotics (oligofructose) (Pro/Pre) or 1 g probiotics (Pediococcus acidilactici, Bactocell®) and 0.5 g xylanase (Pro/Xyl) per kg diet. The supplementation of Pro/Xyl increased ileal digestibility of neutral detergent fibre (NDF) by 41.6% (P < 0.05). The microbial metabolite concentrations, pH of ileal digesta as well as ileal lactobacilli populations were not affected (P > 0.05) by any of the treatments. Enterobacteriaceae were reduced (P < 0.05) upon supplementation of Pro/Pre, resulting in an increased (P < 0.05) ileal lactobacilli to Enterobacteriaceae ratio compared with piglets fed the control diet. In conclusion, NDF digestibility was increased following xylanase supplementation, while microbial activity and composition in the ileum were not affected. The synbiotic approach was effective in reducing ileal Enterobacteriaceae numbers.