Effects of Probiotic on Immune Response and Intestine Morphology of Broiler Chicks Exposed to Stress Induced by Corticosterone

This experiment investigated the effects of different doses of Bacillus subtilis spore as a probiotic on the immune response, intestinal morphology and ileal dry matter digestibility in broiler chicks exposed to stress induced by corticosterone (CORT). Two hundred and eighty-eight one-day-old Ross 308 male broiler chicks were randomly assigned to six treatments in a completely randomized factorial design with and without CORT injection and 3 levels (0, 0.8×10^6, and 1.6×10^6 cfu/g) of B. subtilis spore supplementation. At 7 to 9 days of age (for 3 days), the chicks received one of the subcutaneous injections of CORT or corn oil (as control) at 2 mg/kg BW twice a day. The same injections were repeated at 25 to 27 days of age. Corticosterone injection led to significant (P 0.05) cchanges in intestinal morphology including villus height, ratio of villus height to crypt depth, and dry matter digestibility (as measured by TiO2 marker). These same parameters, however, increased in the experimental chicks relative to the control as a result of probiotic supplementation. Heterophil/lymphocyte ratio increased (P 0.05) as a result of corticosterone injection but exhibited no significant effect of probiotic supplementation. While corticosterone injection decreased lymphocyte density in the medulla of the bursa of Fabricius, this adverse effect was reversed by probiotic supplementation, which was more effective at a 1.6 × 10^6 concentration than at 0.8 × 10^6. As a general conclusion, it may be claimed that administration of B. subtilisbased probiotic alleviates certain negative effects of the stress induced by the corticosterone injection.