Effects of Dietary Supplementation with Aspergillus Awamori on Growth Performance and Antioxidative Status of Broiler Chickens Exposed to High Ambient Temperature

This study was conducted to evaluate the effects of dietary supplementation with Aspergillus awamori on the growth performance and antioxidative status in male broiler chickens exposed to high ambient temperatures. Twenty-four 15-d-old male broiler chickens were randomly divided into 2 dietary groups fed a corn-soybean meal-based diet supplemented without or with 0.05% of Asp. awamori. Six birds of each dietary group were kept under a thermoneutral condition (22 degrees C), and 6 birds were exposed to heat stress (35 degrees C, 9 h/d) for 15 d. Dietary Asp. awamori decreased feed intake and improved the feed conversion ratio in chickens kept at 22 degrees C. Body weight gain and feed intake were decreased in chickens exposed to heat stress. There was no beneficial effect of dietary Asp. awamori on growth performance under the heat stress condition. However, the malondialdehyde content in skeletal muscle, as an index of lipid peroxidation, was decreased by dietary Asp. awamori in chickens kept at 22 degrees C. Although the malondialdehyde content increased under the heat stress condition, dietary Asp. awamori alleviated the increased malondialdehyde. In addition, the alpha-tocopherol content in skeletal muscle was negatively affected by the exposure to heat stress, and dietary Asp. awamori recovered the reduction in the alpha-tocopherol content. Moreover, mRNA expression of glutathione peroxidase in liver was increased by dietary Asp. awamori under both of the thermal conditions. In conclusion, this study shows that dietary Asp. awamori improves the diminished antioxidative status under the heat stress condition partially because of its effect on the expression of hepatic antioxidant enzymes in broilers.