Effect of probiotic supplementation on productive performance and epithelial intestinal integrity of broiler chickens exposed to heat stress.

Heat stress (HS) impacts performance and intestinal homeostasis of broiler chickens. Probiotic represents an alternative to counteract those negative effects. This study evaluated the performance and intestinal integrity of HS chickens supplemented with a B. subtilis based probiotic in two 35-d periods. Period 1 was conducted under thermoneutral conditions (TN; 25.7 ± 1.7 °C) using 150 one-day old chickens (Ross-308) randomly assigned to two dietary treatments: TN birds fed a standard diet without (TN-S) or added with 0.05% probiotic (TN-P). Period 2 was conducted under HS (29.3 ± 2.6 °C) with 120 one-day old chickens fed the standard diet without (HS-S) or with 0.05% probiotic (HS-P). On day 35, ten birds per treatment were sacrificed and jejunum was collected. HS and probiotic supplementation reduced feed intake from d-1 to d-35 (P < 0.01). Feed conversion from day 1 to 21 was better in HS compared to TN chickens, but the opposite occurred from d-1 to d-35 (P < 0.01). Overall, from d-1 to d-35, body weight and daily gain were lower in HS than TN chickens (P < 0.01), but these variables were higher in HS-P than HS-S chickens (P < 0.05). HS chickens reduced villi height, and crypt depth, and increased villi height:crypt depth ratio compared to TN chickens (P < 0.01), but probiotic supplementation increased them (P < 0.01). Probiotic supplementation increased claudin-5 expression during TN and HS periods (P < 0.05), and TJP-1 during TN period (P < 0.05), but decreased occludin expression during HS (P < 0.05). In general, Bacillus subtilis supplementation positively impacts performance and epithelium integrity of the small intestine of HS broiler chickens.