The Effect of Heat Stress on Broiler Meat Quality and the Mechanisms Underlying Muscle Acidification: An In Vivo and In Vitro Study

Background: This study investigated how chronic heat stress affects meat quality and post-slaughter muscle acidification in slow-growing yellow-feathered broilers, focusing on the roles of ALDOB and HSP90B1 in glycometabolism. Methods: From 100 to 120 days of age, broilers were kept either under thermoneutral conditions (25 ± 1 °C, N group) or cyclic heat stress (32 ± 1 °C for 9 h/day, H group). Meat quality traits (pH, shear force, drip loss, color) were measured at 0, 24, and 48 h of refrigeration (4 °C). Free amino acid and fatty acid profiles were analyzed. DF-1 cells were exposed to 43 °C for functional assays of ALDOB and HSP90B1. Results: Chronic heat stress reduced body weight, altered flavor precursors, and induced PSE-like characteristics (lower pH, higher shear force, increased drip loss, paler color), especially in leg muscles. ALDOB and HSP90B1 were upregulated in both tissues and cells. ALDOB overexpression promoted glucose consumption, while HSP90B1 suppressed lactic acid production. Conclusions: Chronic heat stress impairs growth and flavor precursors and exacerbates post-slaughter muscle acidification (primarily driven by ATP hydrolysis, with lactic acid as a secondary contributor). ALDOB and HSP90B1 may dually regulate glycometabolism under heat stress.