The effect of increasing dietary Vitamin E and D doses on the performance of broilers and CLDN2 gene expression during experimental heat stress.

This study aimed to evaluate the effects of increased doses of vitamins E and D on broiler performance, blood parameters, and intestinal CLDN2 gene expression under heat stress (HS). Four hundred broilers were allocated to five groups: a negative control (C-) receiving recommended vitamin levels without HS exposure, a positive control (C+) exposed to HS without additional vitamin supplementation, a group receiving a higher dose of vitamin D (6000 IU/kg) during HS (D6), a group receiving a higher dose of vitamin E (100 mg/kg) during HS (E100), and a group receiving a combination of higher doses of vitamins D and E during HS (D6E100). Broiler performance, blood parameters, and intestinal CLDN2 gene expression were assessed. The results showed that blood glucose, ALT, AST, and LDH levels were significantly reduced in the D6E100 group following HS exposure (p< 0.05). Administration of higher vitamin doses increased feed intake and reduced the feed conversion ratio (p< 0.05). Heat stress significantly upregulated intestinal CLDN2 gene expression, whereas supplementation with vitamins D and E significantly downregulated its expression. In conclusion, HS negatively affected broiler performance and increased intestinal CLDN2 gene expression. However, combined supplementation with higher doses of vitamins D and E mitigated these adverse effects, suggesting a potential strategy to enhance broiler resilience under HS conditions. Keywords: Heat stress; Vitamin E; Vitamin D; CLDN2.