Dietary supplementation with mint leaf powder alleviates leaky gut by regulating tight junction protein (TJs) expression in heat-stressed broilers

Heat stress (HS) greatly impacts broiler performance via impaired intestinal barrier function and physiological homeostasis disruption. Mint leaf powder (MP) holds bundle of bioactive components linked to health benefits like essential oils (menthol and menthone) and polyphenolic (rosmarinic acid, quercetin, and kaempferol), promoting medicinal attributes besides antioxidant potentiality. The objective of this study was to examine the potential of dietary supplementation with 18 g MP/kg to ameliorate HS-induced intestinal permeability in broilers. A total of 80 one-day-old male Cobb broiler chickens were randomly assigned to a 2×2 factorial design with four treatments: in thermoneutral conditions (25°C), with 0 or 18 g/kg MP (LMP0, LMP1) and in HS conditions (35°C), with 0 or 18 g/kg MP (HMP0, HMP1). Experimental periods were from 15-42 days (d) of age. Overall, HS reduced final body weight (12-14%), average daily feed intake and average daily gain compared to broilers in thermoneutral conditions (P < 0.01). Dietary supplementation with 18 g MP /kg diet reduced physiological HS metabolic responses, reducing breathing frequency over the HS period, leg temperature, and cloacal temperature of HS birds (P < 0.01) during days (d) 29-35. Molecular analysis showed HS induced a decrease in tight junction proteins, including Claudin-5, ZO-1, and NFκB while also inducing an increase in the expression of heat shock proteins, HSP70 and HSP90 (P < 0.01). Furthermore, MP supplementation partially restored Claudin-5 and NFκB expression of HS birds which may demonstrate improvements in intestinal barrier integrity among HS broilers. In addition, MP modulated the expression of thermosensitive TRPM8 channels and hypothalamic neuropeptides that play key roles in appetite regulation, including AGRP and GLP-1 . HS elevated plasma cortisol (P<0.01), but MP reduced it back to baseline (P<0.01). Collectively, these results highlight that dietary MP supplementation at 18 g/kg provided protective effects against HS induced intestinal barrier dysfunction by preservation tight junction protein expression, modulation of thermosensory pathways, and reduction in stress responses and suggests the potential use of MP as natural feed additives in managing HS in broiler production. • Heat stress (HS) impaired intestinal immune function, body weight and feed intake of broiler chickens. • Dietary supplementation with 18 mg/kg of mint leaf powder (MP) reduced breathing frequency, leg and rectal temperature of HS-birds. • HS decreased expression tight junction proteins (TJs) of Claudin-5, ZO-1, and NFκB against increase expression of HSP70 and HSP90. • MP modulated the expression of thermosensitive TRPM8 channels and hypothalamic neuropeptides of AGRP and GLP-1. • MP alleviated HS induced intestinal barrier dysfunction by preservation TJs, modulation of thermosensory pathways, and reduction in HS responses.