Effects of reversing the light-dark cycle on growth performance and intestinal health in heat-stressed broilers

Heat stress (HS) has severely restricted the growth and yield of poultry. Reversal light-dark cycles (RLD) are a low-cost and highly effective method to regulate circadian rhythms. However, current studies have not demonstrated whether this method can improve the intestinal injury induced by HS in broilers. This research collected the intestinal tissues, and the experiment was carried out by HE staining, molecular biology, 16S rRNA sequencing, and other methods. Our results show that HS not only hinders the growth and development of broilers but also leads to increased stress levels in the body and impairs intestinal function. RLD treatment increased significantly the body weight of broilers, alleviated oxidative stress caused by HS, promoted the release of melatonin, as well as reduced the expression of cortisol and heat shock protein 70. RLD also induced increased gene and protein expression of tight junction proteins and clock genes, and altered the structure of the cecal microbial community by increasing the abundance of Enterococcus faecalis, Lactobacillus, and Bacteroidetes. Furthermore, the activities of intestinal digestive enzymes and absorption enzymes were significantly improved. In conclusion, RLD improves the growth performance of broilers under HS conditions by reducing the stress response and protecting intestinal function.