SHORT-TERM EFFECTS OF A SINGLE DOSE OF GONADO- TROPHIN RELEASING HORMONE (GnRH) VACCINE ON TES- TICULAR AND EJACULATE CHARACTERISTICS OF DOGS

The short-term effect of gonadotrophin releasing hormone (GnRH) vaccine was evaluated in ten adult male dogs with mean weight of 8.0±1.2 kg, and age ranging between 1 and 3 years. The first group (control) comprised five intact dogs treated with normal saline, while the second group included five dogs treated with a single subcutaneous injection of 400 μg GnRH vaccine. Semen was obtained from the dogs before the administration of the vaccine and thereafter fortnightly up to twelve weeks for determination of semen volume, sperm concentration, motility, percentage live-dead ratio and abnormal spermatozoa percentage. Also, the scrotal circumference of the dogs was measured fortnightly for sixteen weeks. At the end of the 16 week, testis of the control and treated dogs were surgically removed, the short and long axis determined, and fixed in Bouin’s fluid for histopathological examination. The testicular dimension, sperm volume, percentage sperm motility and sperm concentration were presented as mean±SD and compared using repeated measures ANOVA (SPSS 17.0 software). The scrotal circumference was significantly (P<0.05) lower in the treated dogs than in controls. The testicular dimension of control dogs (6.1±0.7 cm) was significantly (P<0.05) bigger than that of treated dogs (4.4±0.3 cm) Histologically, the testes of treated dogs showed clear disruption both in the number and morphology of the interstitial Leydig cells. The mean semen volume, sperm motility, concentration and live-dead ratio decreased (P<0.05) two weeks after treatment in vaccinated dogs, and thereafter the dogs became aspermic. It was concluded that the single injection of GnRH vaccine produced changes in the testes and semen of dogs and infertility up to post vaccination week 16.