Heat stress effect on the intestinal epithelial function of broilers fed methionine supplementation

•24-hour heat stress impairs the performance of broilers at 21 and 42 days of age.•24-hour heat stress and methionine deficiency impairs the intestinal integrity of broilers 21 and 42 days of age.•Heat stress stimulates the expression of genes involved in the immune response in jejunum and ileum.•Heat stress and methionine deficiency increasing expression of genes encoding proteins capable of maintaining intestinal health and integrity.•Methionine supplementation helps cells fight the harmful effects of heat stress. The objective of this study was to evaluate the effect of DL-methionine supplementation on the expression of genes related to immune function and intestinal integrity in the jejunum and ileum of 21- or 42-day-old broilers subjected to 38 °C for 24 h. Broilers of 1–21 and 22–42 days of age were divided into two treatments related to methionine supplementation: without DL-methionine supplementation (MD) or recommended level of DL-methionine (MS). In addition, the animals were either maintained at a comfort environment or exposed to heat stress (HS) (38 °C for 24 h, starting on day 20 or day 41 for Experiments 1 and 2, respectively). Heat stress increased body temperature and the respiratory rate of the birds in both the experimental periods evaluated (1–21 and 22–42 days of age) (body temperature: P = 0.0010 and P = 0.0005, respectively; respiratory rate: P