Selenomethionine alleviates heat stress-induced jejunal injury in broilers by regulating endoplasmic reticulum stress-mediated signaling pathway.

Heat stress (HS) is a major factor limiting broiler production. This study evaluated whether dietary selenomethionine (Se-Met) could attenuate HS-induced jejunal injury in broilers. The assessed outcomes included growth performance, jejunal antioxidant status, digestive enzyme activity, mucosal barrier-related proteins, and endoplasmic reticulum (ER) stress-related protein expression at 35 and 42 days of age. A total of 200 28-day-old Ross 308 broilers were randomly assigned to five groups with four replicates per group and 10 birds per replicate. The thermoneutral control group was maintained at 24 ± 1 °C and fed a basal diet (TN). The HS group was maintained at 33 ± 1 °C and fed the basal diet, whereas the HS0.15, HS0.3, and HS0.6 groups were maintained under HS and fed the basal diet supplemented with 0.15, 0.30, and 0.60 mg/kg Se-Met, respectively. HS affected growth performance and jejunal functional indices to different extents at 35 and 42 days of age. Group differences were observed in (ADFI) at 35 d (P = 0.002) and 42 d (P = 0.027), (ADG) at 35 d (P = 0.015) and 42 d (P < 0.001), and F/G at 42 d (P = 0.001), whereas (F/G) at 35 d did not differ among groups (P = 0.035). Jejunal antioxidant indices also differed among groups, including T-AOC at 35 d (P < 0.001), T-SOD at 35 d (P = 0.035) and 42 d (P < 0.001), and MDA at 35 d (P < 0.001). Compared with the TN group, the HS group showed lower sucrase activity at 35 d (P = 0.018) and 42 d (P < 0.001), lower maltase activity at 35 d (P = 0.019), and lower Occludin expression at 35 d (P = 0.011) and 42 d (P = 0.003). Se-Met supplementation attenuated several HS-associated changes, with the 0.30 mg/kg dose showing the most favorable overall response. At 35 d, Occludin and Claudin-1 expression in the 0.30 mg/kg Se-Met group increased by 9.1% and 9.0%, respectively, compared with the HS group. In conclusion, dietary Se-Met may help reduce HS-associated jejunal dysfunction in broilers, partly by improving antioxidant status and attenuating HS-induced upregulation of ER stress-related proteins, including GRP78, ATF6, PERK, and IRE1. However, Se-Met did not consistently restore all intestinal parameters to thermoneutral levels, and further studies are needed to verify downstream ER stress and apoptosis pathways.