Suppression of fertility in pre-pubertal dogs and cats

Pre-pubertal gonadectomy in dogs and cats is still controversially discussed because some consequences cause health problems. Nevertheless, postponement of puberty, that is, prevention of an increase in sexual hormones and thereby prevention of their manifold effects, is of major importance, not only in controlling overpopulation but also to preserve the genetic base for future breeding stock and pets. Therefore, alternatives for surgical suppression of fertility in pre-pubertal animals were critically reviewed. As a promising alternative, the slow-release GnRH agonist deslorelin and other GnRH analogues have been investigated. In female dogs and cats, puberty could be significantly postponed without initial flare-up effect and without disturbance of body development. First trials to delay puberty in female and male cats by application of a 4.7-mg deslorelin implant 24 h after birth so far are promising. In female dogs, a previous investigation showed that when the implant was inserted at the age of 4 months, the initial flare-up effect was prevented. Body development was normal in the studies reviewed here, and with the 9.4-mg implant, puberty was significantly delayed until the age of 21 months or older. In one study, bitches either received a 4.7- or a 9.4-mg implant at the age of 4 months and the epiphyses were mostly closed before the time of first oestrus. Using a 4.7-mg deslorelin implant in pre-pubertal male dogs significantly postponed puberty, and age at puberty was >2 years when a 9.4-mg implant was used. However, further investigations are required, especially concerning the effect of different GnRH agonist dosages and resorption rates on the duration of postponement of puberty as well as long-term effects in both dogs and cats.