The study reported here described the use of nonsurgical castration with zinc gluconate and compared it with traditional surgical castration in terms of acceptance by dog owners, ease of use, and short-term outcomes. Medical records of male dogs neutered during a May 2004 animal control campaign in the Galapagos Islands were reviewed. Zinc gluconate was provided as a sterile aqueous solution containing 0.2M zinc gluconate (13.1 mg/mL). In the zinc gluconate-treated group, dogs with testes measuring < 10 mm in width received zinc gluconate volumes of 0.1 ml/testicle. Volumes for dogs with testes measuring > 27 mm in width were truncated at 1.0 to 1.1 mL/testicle. The needle was inserted into the dorsocranial aspect of each testicle and directed caudally so that the tip was estimated to be at the center of the testis, and the solution was gently injected. Use of zinc gluconate was well accepted by the dogs. Moderate complications associated with bilateral orchiectomy were limited to wound dehiscence in 2 skin incisions, representing 3.4% (2/58) of dogs. Necrotizing zinc gluconate injection-site reactions occurred in 4 dogs, representing 3.9% (4/103) of dogs. All 4 dogs with severe reactions were large, mature dogs that had received a dose of the drug at the upper end of the label range (3 dogs received 0.8 mL/testicle and 1 dog received 1.0 mL/testicle). Surgical wound complications were treated by superficial wound debridement and resuturing. Zinc gluconate reactions required antimicrobial treatment, orchiectomy, and extensive surgical debridement and reconstruction, including scrotal ablation in 2 dogs. Further investigation is needed to identify risk factors for adverse reactions to zinc gluconate and to develop strategies for avoidance.

COMMENTARY: The ideal sterilizing agent or technique is inexpensive, noninvasive, completely effective, and not associated with side effects. Castration meets some but not all of these criteria, and the same can be said of zinc gluconate as an intratesticular injection. The latter is less invasive than castration and may be associated with fewer long-term side effects because it does not completely suppress testosterone secretion. However, as noted in this study, it is as commonly associated with short-term side effects, which are generally more severe than those of castration and require anesthesia and surgery. Finally, readers should be aware that reports describing efficacy of zinc gluconate often mistakenly consider dogs ejaculating semen samples containing no spermatozoa as equivalent to those dogs from whom they could collect no semen sample, calling them all infertile or sterile.

Comparison of intratesticular injection of zinc gluconate versus surgical castration to sterilize male dogs. Levy JK, Crawford PC, Appel LD, Clifford EL. AM J VET RES 69:140-143, 2008.