L-serine modulates activities of antioxidant enzymes and behavioral responses in broiler chickens subjected to feed restriction during the hot-dry season

Abstract

The aim of the study was to evaluate the effects of L-serine on catalase and glutathione peroxidase activities; latency, rest, number of lines crossed, attempts at jumping, vocalization, defecation, preening rate and tonic immobility of broiler chickens subjected to feed restriction during the hot-dry season. Broiler chicks (n =120) were divided into four groups of 30 each: Group A: feed restriction (FR); Group B: feed restriction + L-serine (FR + L-serine); Group C: feed ad libitum (AL); and Group D: feed ad libitum + L-serine (FR + L-serine). L-serine (200 mg/kg) was administered for 14 days orally from one-day old. Broiler chickens were subjected to 20%-feed restriction from day 7-14 of rearing. The temperature-humidity index recorded from the study period was 30.88 ± 0.81, indicating the chickens were subjected to environmental heat stress. At weeks 3, 4 and 5, serum catalase and glutathione peroxidase activities were evaluated. Tonic immobility and Open-field responses were assessed at weeks 4 and 5. Activities of catalase and glutathione peroxidase increased (P < 0.05) in FR + L-serine and AL + L-serine broiler chickens, compared to FR and AL broiler chickens. Latency duration, and rest and frequency of preening increased (P < 0.05) in FR and AL broiler chickens, compared to FR + L-serine and AL + L-serine broiler chickens. Tonic immobility decreased significantly (P < 0.05) in the following order: AL > FR > AL + L-serine > FR + L-serine broiler chickens. The results show that feed restriction and/or L-serine ameliorated the risk of adverse effects of environmental heat stress by increasing catalase and glutathione peroxidase activities; and by decreasing duration of rest, preening frequency, latency of movement and tonic immobility. In conclusion, L-serine administration and feed restriction, particularly in combination, alleviated the adverse heat stress-induced behavioral responses partly by enhancing activities of catalase and glutathione peroxidase.