Effect of Curcumin Supplement in Summer Diet on Blood Metabolites, Antioxidant Status, Immune Response, and Testicular Gene Expression in Hu Sheep

Simple Summary Heat stress can induce oxidative stress and has an adverse effect on the growth and reproductive performance in animals. Curcumin, a plant-derived substance, with the effect of scavenging oxidative free radicals, improving immune response and anti-apoptosis, has been widely used as a dietary supplement in the livestock industry. The present study aims to investigate the effect of a curcumin dietary supplement on the blood metabolites, antioxidant status, immune response, and testicular gene expression in Hu Sheep in summer. The results show that dietary curcumin supplementation (450 and 900 mg/per sheep daily) can promote lipid metabolism, antioxidant capacity, and immune response as well as testicular development in Hu sheep, which provides evidence for the protective role of curcumin against heat stress in sheep. Abstract In summer, the high temperature affects animal growth and reproductive performance. Curcumin is a flavonoid with anti-oxidant and anti-inflammatory effects. To evaluate the effects of dietary curcumin supplement on the blood biochemical parameters and testicular gene expressions in Hu sheep in summer, a total of 144 male Hu sheep aged four months were randomly divided into three groups (Con, Cur1, and Cur2, n = 48). Sheep in Con, Cur1, and Cur2 groups were fed a basal diet supplement with 0, 450, and 900 mg (per sheep) curcumin daily, respectively. Sheep were fed for 35 days, including a pre-feed for seven days. The results showed that the supplement with 450 mg and 900 mg curcumin increased serum free fatty acid (NEFA) and glutathione peroxidase (GPX), as well as IgA and IgM. The supplement with 450 mg curcumin increased the IgG level, while the supplement with 900 mg curcumin had a lower IgG level than the supplement with 450 mg curcumin (p < 0.05). Dietary curcumin supplement increased testicular organ index, serum testosterone level, and testicular star mRNA expression (p < 0.05). Furthermore, dietary curcumin supplement linearly inhibited testicular apoptosis with increased testicular bcl-2 mRNA expression and decreased caspase-3 mRNA expression (p < 0.05). In conclusion, dietary curcumin supplement can promote lipid metabolism, antioxidant capacity, and immune response, as well as testicular development, in Hu sheep, which provides evidence of application of curcumin in sheep production.