[GnRH agonist implants in small animal practice - what do we know 13 years following EU registration?]

The availability of GnRH agonist implants offers the possibility of a reversible, temporary downregulation of endocrine and germinative testicular function in male dogs and hobs. This review provides an overview of the registered indication, the induction of temporary infertility in healthy, intact, sexually mature male dogs (4.7 and 9.4 mg deslorelin) and hobs (9.4 mg deslorelin) as well as various off-label indications. Off-label use requires strict indications, informed consent from the owner and a lack of licensed medication (safe and optimum effect). Off-label indications in the male dog include sexual-hormone dependant (disturbing) behavior, benign prostatic hyperplasia, small adenomas of the hepatoid glands and alopecia X. Successful use of deslorelin implants for estrus suppression in jils, but also for the treatment of hyperadrenocorticism in ferrets in general have been described. Similarly, hormonal castration can be induced in tomcats and queens. The variable time to onset of effect and its duration (extremely variable in some animals) represent a challenge for breeders. No (sufficient) contraceptive activity was identified in male rabbits and male guinea pigs; however, treatment did successfully suppress the estrus cycle in female individuals of these species, as well as reproductive activity in male and female rats. Regarding the use in birds and reptiles, significant species-specific differences exist with regard to efficacy, time until onset of effect and duration of downregulation. In birds, the implant is efficient to fully suppress egg laying in chicken, Japanese quail and psittacids. In doves, egg laying is only significantly reduced. Successful treatment of reproduction-associated (unwanted) behaviour patterns (feather picking, aggression) has also been described. In some male birds, namely zebrafinch and Japanese quail, the deslorelin implant is suitable to reduce testosterone levels. Successful treatment of hormone-dependent tumours (Sertoli-cell tumorus) in budgerigars has been described as well as the modulation of specific behavior in turkeys and an efficacy in facilitating their keeping (i. e. reduction of aggression). In reptiles, only the successful use of deslorelin in iguana has been demonstrated to date.

Contraceptive efficacy and dose-response effects of the gonadotrophin-releasing hormone (GnRH) agonist deslorelin in Tasmanian devils (Sarcophilus harrisii)

Contraception is increasingly used to manage breeding opportunities in conservation-dependent species. This study aimed to determine the efficacy, duration of effect, optimal dose and potential side effects of Suprelorin contraceptive implants in Tasmanian devils, for use in the conservation breeding program. In our pilot study, Suprelorin was found to effectively suppress oestrous cycles in female devils, yet caused a paradoxical increase in testosterone in males. Therefore, we focussed on females in further trials. Females received one (n=5), two (n=5) or no (n=5) Suprelorin implants, with quarterly gonadotrophin-releasing hormone (GnRH) challenges used to test pituitary responsiveness over two breeding seasons. Both Suprelorin doses suppressed pituitary responsiveness for at least one breeding season, with a reduced effect in the second. There was a dose-response effect on duration rather than magnitude of effect, with high-dose devils remaining suppressed for longer than low-dose animals. There were no apparent negative effects on general health, yet captivity and contraception together may cause weight gain. Suprelorin contraceptive implants are now routinely used in the Save the Tasmanian Devil Program insurance metapopulation to meet the aims of maintaining genetic and behavioural integrity by controlling individual reproductive contributions in group housing situations.

Gonadotrophin-Releasing Hormone Agonists and Other Contraceptive Medications in Exotic Companion Animals

The use of a gonadotrophin-releasing hormone agonist slow-release implant (GnRH A-SRI) has become increasingly popular as an alternative for surgical contraception in many species. Although these implants have proven to be very effective in some species (eg, ferrets, rats, chicken, psittacines, and iguanas), they have been found less effective in other species (eg, male guinea pigs and rabbits, veiled chameleons, slider turtles, and leopard geckos). This review provides an overview of the available literature on the effects of GnRH A-SRIs in companion exotic animals.

Disorders of the Reproductive Tract of Rabbits

Disorders of the reproductive tract are common in rabbits. Conditions are different in rabbits that are farmed for their meat or fur and those that are kept as pets. Farmed rabbits suffer from infections and diseases associated with pregnancy. Congenital abnormalities are more likely to be recognized and treated in pet rabbits. Pet rabbits suffer from age-related changes to their genital tract (hyperplasia, neoplasia, or hernias). Neutering is an important part of prevention and treatment of reproductive disorders. Knowledge of normal male and female reproductive anatomy is essential to prevent complications. These are described and illustrated.