Effect of dietary quercetin on growth performance, blood parameters and testicular development of Hu sheep in summer

To evaluate the effects of dietary quercetin on growth performance, blood parameters and testicular development of Hu sheep in summer, 96 lambs (25.51±0.23 kg) aged 4 months were randomly assigned to two groups (Con and Que, n=48), fed a basal diet supplemented without (Con) or with 3.75 g/d (Que) quercetin, respectively. Lambs were fed for 5 weeks including a pre-trial adaption of 1 week. Feed intake and body weight were recorded, blood samples and testicular tissues were collected to detect the biological indexes, immunoglobulins, antioxidants, hormones, testicular spermatogenic epithelium and steroidogenic proteins. Results showed that quercetin supplement decreased feed intake very significantly (P<0.01) without affecting average daily gain; increased serum NEFA level significantly (P＜0.05) without affecting concentrations of Glu, TC, TG, HDL, or LDL. Quercetin supplement increased the activity of serum GPX, and concentrations of plasma IgA, IgM, and IgG very significantly (P<0.01); However, it did not significantly affect T-AOC level or SOD activity. Quercetin supplement reduced T3 concentration numerically (P=0.050) without changing plasma T4 or cortisol concentration (P>0.05). Testicular spermatogenic cells in the Que group were arranged in a more organized manner with a thicker epithelium (P<0.01), and plasma testosterone increased numerically compared with that in the Con group (P=0.071). WB analysis showed that quercetin supplement increased testicular HSD3B expression very significantly (P<0.01) without affecting StAR, P450scc, or CYP17 expressions. In conclusion, dietary supplement of quercetin at 3.75 g/d in summer can decrease food intake without affecting the body weight, promote lipid metabolism, antioxidant capacity, immune response and improve the structure of testicular spermatogenic epithelium in Hu sheep, which provide evidences for further application of quercetin in sheep production.