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 <italic>Bacillus licheniformis</italic> and <italic>Bacillus subtilis</italic> 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: CON (basal diet), T1 (CON + <italic>Bacillus subtilis</italic>), T2 (CON + <italic>Bacillus licheniformis</italic>), or T3 (CON + both <italic>Bacillus</italic> strains). After 28 days, Pigs fed T3 had the highest body weight, although the difference was not statistically significant. <italic>Bacillus</italic>-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 in T2 and T3, with villus height, villus/crypt ratio, and smooth circular muscle thickness showing notable increases. The tight junction proteins were significantly ex-pressed higher in all <italic>Bacillus</italic>-treated groups, with T3 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 T3. These results suggest that combining <italic>Bacillus subtilis</italic> and <italic>Bacillus licheniformis</italic> synergistically enhances intestinal morphology and barrier function, highlighting their potential as functional feed additives.