A flavonoid extract from Bupleurum aerial parts given at recovery onset attenuates residual liver and lung injury in yellow-feathered broilers after acute heat exposure.

Most broiler heat stress studies focus on the exposure phase, whereas the first hours after heat withdrawal remain understudied. We tested whether a flavonoid extract from Bupleurum aerial parts (BAPF), administered at recovery onset, could reduce residual liver and lung injury in yellow-feathered broilers exposed to 35 °C for 6 h and then cooled to 24 °C over the next 6 h. The extract improved liver and lung histology, lowered serum injury markers and circulating interleukin-1β and interleukin-18, and improved hepatic redox indices, with the most consistent responses at 46 to 68 mg/kg body weight per day. Exploratory composite analysis also prioritized the 46 to 68 mg/kg body weight per day range. In a separate heat and rewarming model using the chicken fibroblast cell line DF-1, the extract added at recovery onset lowered reactive oxygen species, increased nuclear abundance of nuclear factor erythroid 2-related factor 2, and reduced immunoblot signals for NLR family pyrin domain containing 3, cleaved caspase-1, cleaved caspase-3, and cleaved gasdermin E. An ML385 pretreatment arm attenuated several of these changes, supporting involvement of this pathway. Overall, the findings suggest that early recovery after heat exposure may provide a post-heat intervention window and warrant further evaluation of BAPF initiated at recovery onset to limit residual organ injury in yellow-feathered broilers.