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

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 degrees 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 degrees 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 < 0.0001). Experiment 1 (1-21-day-old broilers): in the jejunum, we observed higher heat shock protein 70 kDA (HSP70) gene expression in HS broilers fed the MD diet (P = 0.0010). Broilers from HS presented higher expression of lipopolysaccharide-induced tumor necrosis factor (TNF)-alpha factor (LITAF) (P = 0.0001), interleukin-1 beta (IL1B) (P = 0.0003), and claudin 1 (CLDN1) (P = 0.0391). Regarding the diet effect, the highest LITAF (P = 0.0002) and IL1B (P = 0.0067) gene expression was observed in birds fed the MD diet. In the ileum, birds from comfort and fed the MD diet presented the highest ILIB expression (P < 0.0001). Broilers from HS presented higher occludin (OCLN) expression (P = 0.0072).Experiment 2 (22-42-day-old broilers): in the jejunum, broilers from HS presented higher LITAF (P < 0.0001) and OCLN (P < 0.0001) expression gene. Broilers fed the MS diet presented higher LITAF (P = 0.0007) and ILIB (P = 0.0220) gene expression. The highest HSP70 (P < 0.0001) and CLDN1 (P = 0.0349) gene expression was observed in HS broilers fed the MD diet. In the ileum, we observed that broilers submitted to HS presented higher HSP70 (P = 0.0008), LITAF (P = 0.0044), and OCLN (P < 0.0001) gene expression. Broilers fed the MD diet presented lower CLDN1 gene expression (P = 0.0141). Our results suggest that methionine supplementation in adequate amounts may assist the body in combating the deleterious effects of stress by stimulating the expression of genes capable of maintaining intestinal epithelial cell function.