Dietary supplementation with high-dose Bacillus subtilis or Lactobacillus reuteri modulates cellular and humoral immunities and improves performance in weaned piglets

Bacilli and Lactobacilli, especially high doses of them are often used as probiotics in piglets. The present study aimed to determine the effects of supplementing a piglet diet with high-dose Bacillus subtilis M-1 and Lactobacillus reuteri X-1. A total of 32 piglets with an initial body weight of 5.8 +/- 0.10 kg were weaned at 21 d of age and randomly allocated into one of four groups with eight replications of one pig: Group 1, assay diet supplemented with Bacillus subtilis M-1 (10(11) cfu kg(-1)); Group 2, assay diet supplemented with Lactobacillus reuteri X-1 (10(11) cfu kg(-1)); Group 3, assay diet supplemented with a combination of Bacillus subtilis M-1 and Lactobacillus reuteri X-1 (0.5x10(11) cfu kg(-1), respectively); control group, assay diet without bacterial supplement. Compared with the other groups, Group 2 showed an increase in feed intake (P > 0.05) and the highest ADG (P < 0.05), while Group I showed the best dry matter intake: gain ratio (P < 0.05). However, the three treatment groups (Group 1-3) all showed significant decreases in serum IgG and IgM concentrations (P < 0.05). Serum TNF-alpha, IL-6 and NO levels in Group 3 were decreased (P < 0.05) compared to those in the control group. Serum DAO and D-lactate concentrations were increased in all of the treatment groups (P < 0.05), compared to those in the control group. These findings show that the addition of high-dose Bacillus subtilis M-1 or Lactobacillus reuteri X-1 to the diet improved growth performance but impaired immunity in weaned piglets.