Interactive effects of glutamine and gamma-aminobutyric acid on growth performance and skeletal muscle amino acid metabolism of 22-42-day-old broilers exposed to hot environment.

Abstract

The present experiment was conducted to investigate the interactive effects between dietary glutamine (Gln, 0 and 5g/kg) and gamma-aminobutyric acid (GABA, 0 and 100mg/kg) on growth performance and amino acid (AA) metabolism of broilers under hot environment. A total of 360 22-day-old Arbor Acres male chickens were randomly assigned to five treatment groups under thermoneutral chamber (PC, 23°C) and cyclic heat stress (HS, 30-34°C cycling) conditions. Compared with the PC group, cyclic HS decreased (P < 0.05) daily weight gain (DWG), daily feed consumption (DFC), the concentrations of Gln, glutamate (Glu), and GABA, and the activities of glutaminase and glutamic acid decarboxylase (GAD) in breast muscle at 28, 35, and 42days, while it increased (P < 0.05) the activities of glutamine synthetase (GS) and gamma-aminobutyric acid transaminase (GABA-T) at 28, 35, and 42days. Dietary Gln and GABA improved (P < 0.05) DWG and DFC of broilers under cyclic HS during 28-42days. In breast muscle, the Gln supplementation increased (P < 0.05) the concentrations of Gln (28, 35, and 42days), Glu (28, 35, and 42days), and GABA (42days) and the activities of glutaminase (28, 35, and 42days) and GAD (28, 35, and 42days) but decreased (P < 0.05) GS activities at 28, 35, and 42days and GABA-T activities at 28days. The addition of GABA increased (P < 0.05) the concentrations of Gln and Glu and activities of glutaminase and GAD, while it decreased (P < 0.05) GABA-T activities at 28, 35, and 42days. Significant interactions (P < 0.05) between Gln and GABA were found on breast skeletal muscle Gln concentrations, glutaminase activities, GS activities at 28 and 35days, and DWG, GABA concentrations, and GABA-T activities at 28, 35, and 42days in broilers under cyclic HS. In conclusion, the present results indicated that the interactions of exogenous Gln and GABA could offer a potential nutritional strategy to prevent HS-related depression in skeletal muscle Gln and GABA metabolism of broilers.