Suppression of inflammatory responses in heat-stressed broiler chickens by bovine casein.

This study was conducted to investigate the potential of bovine casein to mitigate the inflammatory responses in heat-stressed broiler chickens. One-day-old Ross 308 male broiler chickens (n = 1200) were reared using standard management practices. On d 22 of age, birds were divided into 2 main groups and kept either under thermoneutral temperature (21 ± 1 °C) or chronic heat stress (30 ± 1 °C). Each group was further divided into 2 sub-groups and fed either the control diet (Con) or the casein (3 g/kg) supplemented diet (CAS). The study consisted of four treatments; each treatment was replicated 12 times with 25 birds per replicate. The treatments were as follow; CCon: control temperature + control diet, CCAS: control temperature + casein diet, HCon: heat stress + control diet, and HCAS: heat stress + casein diet. The casein and heat stress protocols were applied from d 22 to d 35 of age. Casein increased the growth performance of the HCAS (P < 0.05) when compared to the HCon. Additionally, the maximum feed conversion efficiency was exhibited (P < 0.05) by the HCAS. Compared with CCon, heat stress increased (P < 0.05) the levels of proinflammatory cytokines. Casein lowered (P < 0.05) the levels of proinflammatory cytokines and increased (P < 0.05) the levels of anti-inflammatory cytokines in response to heat exposure. Heat stress decreased (P < 0.05) villus height, crypt depth, villus surface area, and absorptive epithelial cell area. Casein increased (P < 0.05) villus height, crypt depth, villus surface area, and absorptive epithelial cell area in CCAS and HCAS. Furthermore, casein improved intestinal microflora balance by enhancing (P < 0.05) the growth of intestinal beneficial bacteria and decreasing (P < 0.05) the intestinal colonization with the pathogenic bacteria. In conclusion, dietary inclusion of bovine casein would suppress the inflammatory responses in heat-stressed broiler chickens. Such potential could be utilized as an effective management approach to promote gut health and homeostasis during heat stress conditions.