Effects Of Supplement With Letrozole On The Hormone Level In Plasma, Seminal Plasma And Semen Quality Of Bulls

Letrozole(LE) is a third-generation non-steroidal aromatase inhibitor in the body to inhibit testosterone and androstenedione conversion to estradiol and estrone, which increase androgen levels in the body. In this experiment, to study the possibility of using LE to improve semen quality of Simmental bulls, different levels of LE was supplied on Simmental bulls, to dertermine hormone levels in plasma, seminal plasma and semen quality of Simmental bull. The study chose average age of 4 years old and body weight 951±111kg. Thirty-five Simmental bulls healthy and normal semen. We adopt single-factor multi-level test design.Thirty-five Simmental bulls were randomly devided into five groups(n=7): experimental group I(basal diet+50 mg/d LE), experimental group II(basal diet+100 mg/d LE), experimental group III(basal diet+150 mg/d LE), experimental group IV(basal diet+200 mg/d LE), control group(basal diet+0 mg/d LE), LE was fed together with concentrate supplement at six p.m one time per day. The trial duration was 100 days. In the 0 d, 20 d, 40 d, 60 d, 80 d, 100 d, after feeding 2 h. Artificial vigna semen was used to collect semen to determine semen quality and take 0 d, 60 d, 100 d of senmen obtained semen plasma to determine seminal plasma hormone levels, jugular vein blood was collected on an empty stomach in the morning to determinate plasma hormone levels. The results showed that supplement with different levels of letrozole increased androgen levels and reduced estrogen levels in plasma and seminal plasma. In the androgen, the content of androstenedione and testosterone levels increased significantly(P<0.01).In the estrogen, the content of estrone and estradiol decreased significantly(P<0.01), and improved the body's antioxidant capacity, lower malondialdehyde content. However, there was no significant effect on the content of follicle-stimulating hormone and luteinizing hormone. In addition, by supplement with different levels of letrozole, the experimental group semen volume and sperm motility were higher than the control group, and the test group II improved the bull semen volume and sperm motility significantly(P<0.01). The results of this study showed that supplement with LE can increased the content of endogenous A significantly, and reduced the content of E1 and E2; supplement with LE can increase T-AOC and the content of MDA; supplement with LE can increased semen volume and sperm motility significantly. There are four different levels of supplements with LE:50 mg/d, 100 mg/d, 150 mg/d, 200 mg/d, the best addition amount is 100 mg/d.