Effect of probiotic supplementation on growth performance, intestinal morphology, barrier integrity, and inflammatory response in broilers subjected to cyclic heat stress

This study investigated the protective effects of probiotic on heat stress-induced intestinal injury and inflammatory response in broilers. A total of 180 male broilers were randomly allocated to three treatments with four replicates each from 22 to 42 days of age. The broilers were either raised under thermoneutral (TN) conditions (23 +/- 1 degrees C) or subjected to cyclic heat stress (28-35-28 degrees C for 12 hr daily). The broilers kept at TN conditions were fed a basal diet, and those exposed to heat stress were fed basal diets supplemented with or without probiotic at a dose of 1.5 x 10(8) cfu/kg. Compared with the TN group, heat stress decreased (p <.05) the growth performance, reduced (p <.05) villus height and villus height: crypt depth ratio in intestinal mucosa, increased (p <.05) serum levels of D-lactic acid on day 28 and endotoxin, TNF-alpha and IL-6 on day 42, and decreased (p <.05) serum IL-10 content on day 42. Dietary supplementation of probiotic reversed (p <.05) all these changes except for the growth performance in heat-stressed broilers. In conclusion, dietary inclusion of probiotic could improve intestinal morphology and barrier function, alleviate inflammatory response, but exert no ameliorative effect on growth performance of broilers under cyclic heat stress.