Clinical use of deslorelin implants for the long-term contraception in prepubertal bitches: effects on epiphyseal closure, body development, and time to puberty.

Long-acting GnRH agonists have been used both for canine estrus induction and prevention. The objective of the study was to investigate the use of a deslorelin implant as a long-term and reversible contraceptive in prepubertal bitches with special regard to the time of epiphyseal closure. Thirteen healthy, crossbreed, medium-sized prepubertal female dogs were used in this study. An implant containing 9.4 mg (G1, n = 5) and 4.7 mg (G2, n = 4) deslorelin acetate (Suprelorin) or a placebo (sodium chloride 0.9%; G3, n = 4) was inserted subcutaneously in the interscapular region. Estrus was monitored once daily by physical and sexual behavioral changes. Body development, vaginal cytology, and serum progesterone and estradiol 17β concentration were monitored weekly for the first 5 weeks, and then every 3 weeks throughout the treatment period. Radiographic examinations were performed monthly to determine the epiphyseal closure. Half of the deslorelin-treated bitches (G1: n = 2 and G2: n = 2) came into estrus during the 83-week observation period. All animals in the control group showed estrus between the 39th and 64th weeks of observation. Time to puberty averaged 82.7 ± 8.9 and 61.9 ± 9.7 weeks in the deslorelin-treated (G1 and G2) and the control bitches, respectively (P < 0.02). Both deslorelin implants (9.4 and 4.7 mg) can be used efficiently for the long-term prevention of estrus in prepubertal bitches; however, epiphyseal closure is clearly delayed which was without any clinical effect in the present study.