Route-dependent efficacy of wild mint (Mentha longifolia) extract supplementation in heat-stressed broilers:...

Heat exposure can impair intestinal function, physiological homeostasis, and productive performance in broiler chickens. This study evaluated the effects of wild mint powder extract (WMPE) according to administration route and treatment level in Cobb broiler chickens reared under summer heat conditions. A total of 600 one-week-old Cobb broiler chickens were allocated to a 2 × 5 factorial arrangements comprising two administration routes (drinking water or feed) and five treatment levels (negative control, antibiotic control, and WMPE supplementation at 1, 2, or 4 mL/kg or L, according to the administration route). Significant administration route × treatment interactions were observed for cecal total bacterial and Clostridium counts, intestinal villous length, villous width, absorptive surface area, and growth performance (P<0.001). WMPE supplementation generally reduced cecal bacterial populations and improved intestinal morphometric characteristics, although the magnitude of these responses differed between administration routes and treatment levels. In particular, birds receiving 4 mL WMPE/L through drinking water exhibited the highest final body weight and daily body weight gain, whereas the corresponding dietary treatment produced a less pronounced growth response. Significant route × treatment interactions were also detected for serum lipid profile, antioxidant status, and immunoglobulin concentrations (P<0.0001). The dietary administration of 4 mL WMPE/kg produced the most pronounced responses in several antioxidant and lipid-related variables, whereas the highest serum IgG concentration was observed in birds receiving 1 mL WMPE/L through drinking water. Significant interactions were further detected for selected serum biochemical variables, carcass characteristics, and meat composition (P<0.05). Overall, the findings demonstrate that the biological responses to WMPE differed according to both administration route and treatment level, and that the most favorable response depended on the specific outcome evaluated. These findings emphasize the importance of administration route when assessing WMPE as a phytogenic supplement for broiler chickens exposed to summer heat conditions.