Effects of Bacillus licheniformis and Bacillus subtilis on growth performance, gut health, and immunity in pigs.

This study evaluated the effects of dietary supplementation with Bacillus licheniformis and Bacillus subtilis on the gut health and growth performance of weaning pigs. A total of 28-day-old piglets (n = 50 per group) were randomly assigned to four groups: CTRL (basal diet), BS (basal diet + Bacillus subtilis), BL (basal diet + Bacillus licheniformis), or BSL (basal diet + both Bacillus strains). After 28 days, pigs fed BSL had the highest body weight, although the difference was not statistically significant. Bacillus-treated pigs showed no differences in inflammatory cytokines or hematological characteristics, except for a reduction in cortisol levels in the supplemented groups. The genes encoding inflammatory cytokines were not significantly expressed among the groups. Intestinal morphology was significantly improved with villus height, villus/crypt ratio in BL (p < 0.05) and BSL (p < 0.01), and smooth circular muscle thickness showing notable increases in BS (p < 0.05), BL (p < 0.001) and BSL (p < 0.001). The tight junction proteins were significantly expressed higher in all Bacillus-treated groups, with BSL (p < 0.001) exhibiting the greatest improvement. Gene expression levels of ZO-1 and occludin were also significantly elevated in the ileum, with the most pronounced increases observed in BSL (p < 0.01). These results suggest that combining Bacillus subtilis and Bacillus licheniformis synergistically enhances intestinal morphology and barrier function, highlighting their potential as functional feed additives.