The effects of subcutaneous GnRH aganist deslorelin implantation on the reproductive system of male dogs

Abstract

The aims of the study were to investigate the effects of GnRH agonist deslorelin on male reproductive system and to evaluate the possibility of subcutaneous deslorelin implantation to control male fertility in dogs. Ten healthy intact male dogs were used in this study. Eight dogs (a treatment group) were subcutaneously treated with deslorelin formulated into an implant by Peptech Animal Health, Australia, at doses between 0.5 to 1 mg/kg body weight and the other two dogs (a control group) received a placebo implantation. Serum testosterone concentrations were evaluated by chemiluminescence immunoassay. The sperm-rich fraction was obtained by digital manipulation and analyzed to evaluate its quality. To determine testicular size, scrotal circumference measurement and testicular volume determination by the method using ultrasonography were performed. Transabdominal ultrasonography was used to determine prostatic volume. All above criteria were measured once before and, every second week after implantation for the first 12 week period, and every forth week for the second 36-week period. A considerable change was shown in the treatment group. Testosterone level significantly decreased (mean percentage decrease, 94.7%) from week 8 to week 24 (p˂0.05). The seminal volume and total number of spermatozoa per ejaculation considerably reduced within 5.2 week (mean percentage decrease, 71.6%) and within 6 weeks (mean percentage decease, 87.1%) after implantation. Ejaculates ceased completely at week 7.5, and the period ejaculates were unobtainable was 28 weeks. Scrotal circumference and total testicular volume significantly declined; mean percentage decrease were 22.7% from week 6 to week 32 and 38.5% from week 6 to week 40, respectively (P˂0.05). Prostatic volume significantly decreased (mean percentage decease, 50.2%) from week 6 to week 44 (P˂0.05). However, serum testosterone concentrations, serum characteristics, testicular size and prostatic volume were completely reversible after long-term suppression. In conclusion, the results of this present study clearly revealed that subcutaneous deslorelin implantation at doses between 0.5-1 mg/kg obviously suppressed reproductive function and fertility in male dogs for a long period.