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Evaluating a non-surgical deslorelin implant for sterility in tom cats

Romagnoli S, Baldan A, Righetti C, Milani C, Mollo A, et al. Semen quality and interval to sterility in tom cats treated with a 94 mg deslorelin implant. J Feline Med Surg. 2016 Jan 13.

Non-surgical control of sterility in domestic animals is becoming an increasingly important topic from several perspectives. Breeders are interested because of the possibility to temporarily prevent pregnancy for short periods of time while maintaining the potential for future breeding use. Trap-Neuter-Return programs and other population control efforts are interested because of the potential for less expensive, invasive, and time consuming methods to achieve sterility compared with surgical castration.

Gonadotrophin-Releasing Hormone (GnRH) is a hormone produced by the brain that stimulates the production of Lutenizing Hormone 9LH) and Follicle Stimulating Hormone (FSH), which in turn stimulate sperm production in males. Deslorelin is a GnRH antagonist (a drug that blocks the action of GnRH) that has been used in Europe and Australia to non-surgically achieve sterility in male dogs.

This paper investigates that use of a 9.4mg deslorelin implant in adult male tom cats and its efficacy in decreasing sperm production, motility, and morphology. 15 privately owned healthy tom cats were recruited to this study by the University of Padova. Cats were intact males between 5 months and 5 years of age.

Semen was collected in cats through urethral catheterization and injection of medetomidine to stimulate semen release. Semen collection was preformed prior to placing the implant, then every 2 weeks for 3 months after. Cats were also administered gonadorelin and serum testosterone assayed, however these results are not reported.

Semen was evaluated for total spermatozoa count, motility, and morphology (detached heads, head/neck/tail abnormalities, or cytoplasmic droplets).  Sterility was defined as a total spermatozoa count of <0.5×106, sperm motility <20% and normal morphology < 20%.

After implantation of deslorein, several cats experienced a transient increase in semen quality during the first month, followed by a gradual decline in sperm numbers and quality until complete sterility was achieved.

Deslorelin implants in this study resulted in sterility in all cats after 70 days based on semen morphology, though half of cats were sterile by the second month post- treatment. It is possible that functional sterility may have been induced prior to this. While this may be effective for fertility control in many situations, the slow onset may prove a barrier to routine use.  This study also demonstrated that semen collection in cats is simple and effective using a medetomidine-based methodology. (MRK)

See also:
Goericke-Pesch S, Georgiev P, Antonov A, et  al. Clinical efficacy of a GnRH-agonist implant containing 4.7 mg deslorelin, Suprelorin, regarding suppression of reproductive function in tomcats. Theriogenology 2011; 75: 803–810.