Heat stress relief for broiler chickens: Dietary Rutin improved growth performance, immunity, antioxidant capacity, histopathologic picture and gene expression profile

Our research aimed to explore the performance, immunity, antioxidants, gene expression, and histopathology of broilers grown at standard temperatures vs those subjected to heat stress (HS) with rutin supplementation. Two hundred forty-one-day-old chicks were randomly allocated into 4 groups. Control group; Rutin group was administered rutin (500 mg/kg food) at ambient temperature; HS group, birds exposed to HS (35 +/- 2 degrees C) for 14 consecutive days; HS + Rutin group was administered the same dosage of rutin, and the birds were then exposed to HS. Molecular docking revealed high binding affinity of rutin toward the growth factors myostatin, insulin-like growth factor receptor-1 (IGFR-1), growth hormone receptor (GHR), heat Shock protein 90 (HSP90), heat Shock factor-1(HSF-1) and HSP70. Rutin not only improved the body weight and feed conversion ratio, but it also considerably reduced the negative effects of HS on growth performance. It also led to decrease in malondialdehyde and pro-inflammatory cytokine levels of interleukin 2 (IL-2), tumor necrosis factor (TNF-alpha), and IL-6, together with an increase in the antioxidant enzymes CAT, GPX, and SOD activity in addition to a considerable improvement in immunoglobulin (IgM, IgG, and IgA) secretion during HS. Interestingly on molecular level, rutin caused an upregulation in expression of HSP90, HSF-1, HSP70, growth related genes (myostatin, IGFR-1, GHR), and downregulation of immune-related genes chemokines [Lipopolysaccharide-induced TNF-alpha factor (LITAF), IL-1 beta, IL-6 gene expression. These changes are further confirmed by histopathological investigation that revealed improvement in hepatic and breast muscle histoarchitecture, increased glycogen and decreased IL-1 beta immunoexpression after rutin supplementation in HS. In conclusion, rutin is an efficient feed additive that improves antioxidant status, growth, and immunological function in HS.