This study investigated the effect of dietary Macleaya cordata extract (MCE) supplementation on the growth performance, serum parameters, and intestinal microbiota of yellow-feather broilers under heat stress. A total of 216 yellow-feather broilers (28-days-old) were randomly allotted into three groups. A control group (CON) (24 ± 2 °C) and heat stress group (HS) (35 ± 2 °C) received a basal diet, and heat-stressed plus MCE groups (HS-MCE) (35 ± 2 °C) were fed the basal diet with 1000 mg/kg MCE for 14 consecutive days. The results revealed that MCE supplementation improved the final body weight, average daily feed intake, average daily gain, and spleen index when compared with the HS group (p < 0.05). In addition, MCE supplementation decreased (p < 0.05) the activities of aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, and creatinine, and increased (p < 0.05) the glucose level and alkaline phosphatase activity in heat-stressed yellow-feathered broilers. Moreover, MCE treatment alleviated heat-stress-induced intestinal flora disturbances, decreased the Bacteroidota and Bacteroides relative abundances, and increased Firmicutes. A linear discriminant analysis effect size analysis found five differentially abundant taxa in the HS-MCE group, including Alistipes, Rikenellaceae, Mogibacterium, Butyrivibrio, and Lachnospira. These results suggest that MCE can alleviate HS-induced decline in growth performance by modulating blood biochemical markers and cecal flora composition in broilers.

Heat stress (HS) leads to disturbance of homeostasis and gut microbiota. Macleaya cordata extract (MCE) has anti-inflammatory, antibacterial, and gut health maintenance properties. Still, the specific effects of MCE on blood biochemical indices and gut microbiota homeostasis in heat-stressed mice are not entirely understood. This study aimed to investigate the impact of MCE on blood biochemical indices and gut microbiota in heat-stressed mice. A control group (CON) (25 °C, n = 6) and HS group (42 °C, n = 6) were gavaged with normal saline 0.2 mL/g body weight/day, and HS plus MCE group (HS-MCE) (42 °C, n = 6) was gavaged with 5 mg MCE/kg/day. HS (2 h/d) on 8–14 d. The experiment lasted 14 days. The results showed that HS increased mice’ serum aspartate transaminase, alanine transferase activities, heat shock protein 70 level, and malondialdehyde concentrations, and decreased serum catalase and superoxide dismutase activities. HS also disrupted microbiota diversity and community structure in mice, increasing the Bacteroidetes and decreasing Firmicutes and Lactobacillus; however, MCE can alleviate the disturbance of biochemical indicators caused by HS and regulate the flora homeostasis. Furthermore, MCE was able to moderate HS-induced metabolic pathways changes in gut microbiota. The Spearman correlation analysis implied that changes in serum redox status potentially correlate with gut microbiota alterations in HS-treated mice.