Mitigating the negative effects of heat stress in broiler chickens using Saccharomyces cerevisiae and ascorbic acid

Abstract

The production of broiler chickens is often affected by fluctuating environmental conditions leading to loses economically during the hot summer season globally. This has resulted in calls to evaluate the non-ventilating measures available for alleviating excessive heat stress in broiler chickens. Antistress and/or antioxidant agents are readily available and potent agents that are considered in mitigating the negative effect of heat stress in broiler chickens‘ production. The research focused on mitigating the negative effects of heat stress using Saccharomyces cerevisiae and ascorbic acid in broiler chickens. Fifty-six broiler chicks were divided into 4 groups of 14 each, control, probiotic-administered, ascorbic acid-administered and probiotic + ascorbic acid-administered. Broiler chickens were fed diet fortified with probiotic at a dose of 1 g/kg of feed and ascorbic acid at a dose of 200 mg/kg of feed from day (D) 1 to D35 of the study period. Cloacal temperature (CT), temperature-humidity index, dry-bulb temperature and relative humidity and in the pen were obtained bi-hourly, from 07h00 – 19h00, while body surface temperature (BST) was measured thrice on D21, D28 and D35 of the study period. Feed intake, water intake and body weight were measured on D7, D14, D21, D28 and D35 of the study. Behavioural parameters were measured on D21, D28 and D35 of the study period. Interleukin 10 (IL-10) gene expression; 8-hydroxyl-2-dioxyguanosine (8-OHdG), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and malondialdehyde (MDA) activities and concentration, respectively, as well as erythrocyte osmotic fragility (EOF), haematology and small intestinal morphology, were evaluated after sacrificing the chickens at the end of the experiment. Ambient temperature parameters were outside the thermoneutral zone which was indicative of thermal stress during this study. Cloacal temperature and body surface temperature (BST) obtained in the treatment groups were significantly higher (P < 0.0001) than those of the control. Water intake and body weight were significantly higher (P < 0.01) in the treatment groups when compared to the control. Improved tonic immobility and vigilance parameters were obtained in the treatment groups when compared with the control group. The administered antioxidants were efficacious in reducing the expression of oxidative gene damage and enhancing that of interleukin-10. Superoxide dismutase, CAT, GPx, EOF and some haematological parameters were significantly lower (P < 0.0001) in the treatment groups when compared with the control. Small intestinal morphometry and goblet cells count were significantly higher (P < 0.0001) in the treatment groups in comparison with the control group. Interestingly, chickens on probiotic and/or ascorbic acid did not display the detrimental effects of heat stress compared to the control group and this was evident in their performance indices. We therefore conclude that both probiotic and ascorbic acid, anti-stress and antioxidant agents show potential to be effective in mitigating the negative effects of heat stress in broiler chickens, while the best performance was obtained in the Saccharomyces cerevisiae group of broiler chickens. Based on this result, production scale studies are recommended.