Effects of betaine and ascorbic acid on tonic immobility, superoxide dismutase and glutathione peroxidase in broiler chickens during the hot-dry season

The aim of the study was to evaluate effects of betaine and ascorbic acid (AA) on tonic immobility (TI), and activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx) in broiler chickens, reared during the hot-dry season. Eighty White Ross breed day-old broilers were divided into 4 groups. Group I (control) was given sterile water; group II, betaine (250 mg/kg); group III, AA (50 mg/kg), and group IV, betaine + AA, at 250 + 50 mg/kg, respectively. The administration was done orally in drinking water and daily for 42 days. The duration of TI of each bird was measured. Serum obtained from blood samples collected from the birds were assayed for activities of the enzymes. The dry-bulb temperature (28.33°C-35.67°C), relative humidity (69.0-93.0%), and temperature-humidity index (27.85-36.1), recorded during the study period showed that the birds were subjected to heat stress. Betaine and its coadministration with AA decreased (P < 0.05) TI duration compared to the control group. Betaine + AA significantly increased (P < 0.01) SOD activity compared with the controls. There were significant increases in GPx activity in broiler chickens in betaine (P < 0.01), AA (P < 0.05), and betaine + AA (P < 0.001) groups, when compared with that of controls. The result demonstrates that betaine and/or AA decreased TI and enhanced activities of the antioxidant enzymes in heat-stressed birds. It is concluded that the administration of betaine and/or AA to broiler chickens alleviates the adverse effects of heat stress by decreasing fearfulness and increasing activities of SOD and GPx enzymes.