Effect of Bacillus licheniformis on the Heat Stress to Adrenal Gland Structure and Plasma CORT Content in Male Rabbits

PurposeTo study the mechanism of Bacillus licheniformis for alleviating heat stress in male rabbits.

MethodNinety male rabbits of similar age and good body condition were selected and randomly divided into normal temperature control group (N), heat stress group (H) and heat stress+B. licheniformis group (H+B). Group N and group H were fed with basic diets. Group H+B was fed with a basic diet+B. licheniformis 1 000 mg/kg. Group H and group H+B were given heat stress stimulation to simulate hot summer temperature. The test period was 30 days. The adrenal index and content of CORT in the plasma of each group were measured. After the test, sections were made and the changes in adrenal gland structure were observed by light and electron microscopes.

ResultsAdrenal weight and adrenal index in group H and group H+B were extremely significantly higher than those in group N (P<0.01). Group H+B was extremely significantly lower than the group H (P<0.01). Observation of adrenal gland structure showed that in group H, the thickness of the adrenal capsule was reduced, the diameter of the cell mass was reduced, and the structure of the adrenal cortex and medulla was severely damaged. Adrenal gland structure in group H+B was obviously improved. The plasma CORT content showed that at the beginning of the experiment (12 hours and 3 days), the CORT level in group H increased significantly (P<0.01), but began to decrease after 10 days. Although the CORT level of group H+B also increased at the beginning, it increased slowly and reached the normal level in the middle and late stages, and there was no significant difference from group N at the 30th day of the test (P>0.05).

ConclusionThe addition of B. licheniformis to the diet can alleviate the damage caused by heat stress stimuli to male rabbits and help maintain their normal reproductive function.