Short-term treatment with deslorelin implants to improve the bucks’ ability to stimulate cyclic activity during the late non-breeding season

Abstract

• Treatment with deslorelin during 5 d induced an increase in testosterone in bucks. • Testosterone concentration increased in all bucks joined with anestrous does. • Response of does to male effect with treated or untreated bucks was similar. The sudden introduction of males to anestrous females stimulates synchronous ovulations. The effectiveness of males to induce this response is androgen dependent. The aim of the present study was to compare the reproductive response of anestrous does to the introduction of teaser bucks treated with or without deslorelin implants, which continuously release a GnRH agonist. While 5 bucks were acutely treated with a single subcutaneous implant containing 7.4 mg of deslorelin (Suprelorin, Virbac) (group Des), other 5 bucks remained as controls (group Con). Each buck was placed with one group of 8 adult females. Deslorelin implants were inserted on Day -6 and from Day 0 to Day 9, bucks were joined with females from 07:00 to 08:00 and from 19:00 to 20:00 every day. Testosterone concentration was measured from blood samples collected twice a day (12 h apart, am/pm) on Days -11, -10, -9 and from Day -6 to Day -1, and collected immediately after buck stimulation from Day 0 to Day 9. Does that came into estrus and that showed short estrous cycles was registered from Day 0 to Day 9. Transrectal ultrasound examination for recording cyclicity on basis of presence of corpus luteum was done between Days 22 and 27, whereas ultrasonographic pregnancy diagnosis was carried out on Day 49. Testosterone concentration was greater in Des than Con bucks before joining them with females (36.0 ± 7.6 nmol/L vs 15.0 ± 6.8 nmol/L; P = 0.04), but the difference disappeared when all the experiment was analyzed together. Non significant differences were observed in reproductive response of does stimulated by treated or control males. Therefore, we concluded that both treated and control bucks were fully capable of inducing reproductive activity in anestrous does.