Gut microbiota contributes to heat tolerance in chickens through metabolic remodeling and suppression of thermogenesis.

The gut microbiota is increasingly recognized as a key regulator of host metabolic adaptation to environmental challenges. However, whether breed-specific gut microbiota contributes to variation in heat tolerance among poultry breeds remains unclear. This study used Cyan-shank partridge chickens, a native Chinese breed with superior environmental adaptability, to investigate the role of the gut microbiota in heat tolerance and its underlying mechanisms. Cyan-shank partridge chickens exhibited a higher inflection point temperature of rectal temperature and greater tolerance to heat stress than Arbor Acres (AA) broilers. Under cyclic heat stress, Cyan-shank partridge chickens maintained lower body temperatures, superior growth performance, and reduced expression of thermogenesis-related genes in skeletal muscle and liver. Concurrently, Cyan-shank partridge chickens exhibited lower cecal microbial α-diversity and a distinct microbial community structure compared with AA broilers. Fecal microbiota transplantation (FMT) of Cyan-shank partridge chickens derived microbiota into AA broilers improved growth performance and reduced the expression of the thermogenesis-related genes under heat stress. FMT also substantially remodeled the recipient gut microbiota, decreasing the abundance of Bacteroides while enriching several potentially beneficial taxa, including Limosilactobacillus and Phascolarctobacterium. Furthermore, untargeted metabolomics revealed profound alterations in microbial metabolic functions, particularly in pathways related to the tricarboxylic acid cycle, amino acid metabolism, and neurotransmitter metabolism. These metabolic functional changes support the potential mechanisms by which the altered microbiota may contribute to the observed improvements. These findings demonstrate that the gut microbiota contributes to the superior heat tolerance of Cyan-shank partridge chickens and that this phenotype can be partially transferred through FMT, accompanied by reduced thermogenic activity in recipient broilers. This study provides a potential microbiota-based strategy for improving the heat tolerance of commercial broilers.