The Effect of Oral Probiotic <i>Bacillus amyloliquefaciens</i> on Intestinal Microbiota, Intestinal Structure, Serum Antioxidant Capacity and Inflammatory Responses of Heat Stressed Rats

This study investigated the effect of <i>Bacillus amyloliquefaciens</i> (<i>BaSC06</i>) in alleviating heat stress in rats. The rats were randomly divided into four groups. Each rat in Group 1 and Group 3 received oral 1 ml/day of PBS, whereas those in Group 2 and Group 4 were administered 1 ml/day of <i>BaSC06</i> (10⁸ CFU/ml). After two weeks, the rats in Groups 3 and 4 were exposed to heat stress at 42°C for 30 min, while those in Groups 1 and 2 were maintained at 25°C. The result showed that oral <i>BaSC06</i> increased abundance of <i>Firmicutes</i> phylum and <i>Ruminococcaceae</i> Family along with reduced level of Bacteroidetes family. Compared to Group 1, the height of small intestine villi increased significantly (<i>P</i> < 0.05) in Group 2, and intestinal villus height and mucosal thickness decreased significantly in Group 3 than that in Group 4 (<i>P</i> < 0.05). The distribution of ZO-1 was disrupted in Group 3 which was ameliorated in Group 4. The number of bacteria in the liver, spleen and mesenteric lymph nodes was significantly higher in Group 3 than other groups (<i>P</i> < 0.05) meanwhile the LPS level in Group 4 decreased significantly compared to Group 3 (<i>P</i> < 0.05). The levels of IL-1, IL-10 , HSP70 and MDA increased significantly (<i>P</i> < 0.05), the activity of CAT decreased significantly (<i>P</i> < 0.05) in Group 3 compared to the other groups. The adverse effects of heat stress can be alleviated by gavage <i>BaSC06</i>, which improve the composition of intestinal microbiota. It is helpful to elucidate the mechanism of probiotics to counteract the negative effects of heat stress.