Impact of heat stress on redox homeostasis in the liver of laying hens and the protective role of antioxidant supplements
D. B. Perederiy, Y. T. Salyha
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Institute of Animal Biology NAAS, 38 V. Stus str., Lviv, 79034, Ukraine
Under intensive poultry farming conditions, heat stress (HS) is a major factor negatively affecting the productivity of laying hens. Elevated ambient temperatures can lead to systemic imbalances, particularly by disrupting the redox homeostasis in liver cells. A primary consequence of HS is the onset of oxidative stress (OS), marked by increased production of reactive oxygen species (ROS) and impaired function of the antioxidant defense system. Recent studies suggest that dietary supplementation with antioxidants such as betaine, taurine, and myo-inositol can enhance the liver’s resistance to oxidative injury. These compounds are thought to stabilize cellular membranes, stimulate antioxidant enzyme activity, and reduce the overall OS burden in the liver of laying hens. This study aimed to evaluate the combined effects of betaine, taurine, and myo-inositol on oxidative stress markers in the liver of laying hens under HS conditions. Thirty-two laying hens were used. The experiment was conducted at the vivarium of the Institute of Animal Biology NAAS, and consisted of two phases: during the first phase, birds were kept at 20 °C for one week (thermoneutral conditions); in the second phase, HS was induced by raising the ambient temperature to 30 °C for 6 hours daily over 7 days. The birds were divided into two groups: a control group fed a standard diet, and an experimental group whose diet was supplemented with 0,5 g/kg betaine, 5 g/kg taurine, and 2 g/kg myo-inositol. Under HS conditions, the control group exhibited a 1,5-fold increase in hepatic LOOH levels (p < 0,001), indicating heightened OS. SOD and CAT activities decreased by 30% (p < 0,01) and 25% (p < 0,001), respectively, compared to thermoneutral conditions. GPx and GR activities declined by 25% (p < 0,05) and 38% (p < 0,05), respectively. In contrast, antioxidant supplementation reduced LOOH levels by 1,4-fold (p < 0,001) and increased SOD and CAT activities by 21% (p < 0,05) and 18% (p < 0,05), respectively. GPx activity rose 1,5-fold (p < 0,01) relative to the control group. These findings confirm the beneficial effects of betaine, taurine, and myo-inositol on the hepatic antioxidant system in laying hens under HS. Their inclusion in poultry diets may serve as a promising strategy to mitigate oxidative damage and support liver function during periods of elevated ambient temperature.
Key words: heat stress, antioxidant supplements, antioxidant protection, enzymes, catalase, superoxide dismutase,hydroperoxides, lipid peroxidation, glutathione peroxidase, reduced glutathione, TBA-active products
