Effect of heat stress and Gln on the protein expression of Nrf2 and Keap1 of the thigh muscle in broilers. a,b,c Groups without common letters differ significantly (P < 0.05); Duncan's test was used to compare statistical differences among the CON, HS, HS-0.5% Gln, HS-1.0% Gln, and HS-1.5% Gln groups. CON = broilers were kept in the normal-temperature environment and fed a basal diet; HS = broilers were kept in the circular heat stress environment and fed a basal diet; HS-0.5% Gln, HS-1.0% Gln, and HS-1.5% Gln = broilers were kept in the circular heat stress environment and fed basal diets supplemented with 0.5, 1.0, and 1.5 Gln. Nrf2, nuclear factor erythroid 2–related 2; Keap1, kelch-like ECH-associated protein 1. The protein expression of each protein of the CON was set to be 1. CON, control; Gln, glutamine; HS, heat stress.