Effects of intratesticular administration of zinc gluconate and dimethyl sulfoxide on clinical, endocrinological, and reproductive parameters in dogs.

Nonsurgical sterilization methods are considered alternative tools for the worldwide challenge represented by canine overpopulation control. Intratesticular injection of zinc gluconate associated with DMSO arises as an option because of the effortless diffusion throughout the testicular parenchyma. This study aimed to verify the effectiveness of a double testicular injection of zinc gluconate associated with DMSO as a chemical contraceptive for male dogs. The study was conducted with 22 dogs treated with two intratesticular injections of the chemical solution (treated group; n = 15) or 0.9% NaCl solution (control group; n = 7) on a monthly interval. All animals were submitted to clinical examination, breeding soundness evaluation including morphologic and sonographic examination of the testes, assessment of libido, volume of the sperm-rich fraction, sperm motility, total sperm count, plasma membrane integrity, sperm morphologic abnormalities, and the total number of morphologically normal and motile sperm in the ejaculate. Blood samples were collected for serum testosterone analysis, and testicular tissue was morphologically and histologically evaluated. No clinical alterations and signs of pain or local sensitivity along the experimental period were noticed. However, the injection of zinc gluconate and DMSO significantly reduced libido and testosterone concentrations (even beyond the reference range for intact male dogs). Impairment of sperm quality-related variables was observed 15 days after the first intratesticular administration of zinc gluconate and DMSO (i.e., decrease in sperm count and sperm motility and an increase in major sperm defects and by this a decrease in the total number of morphologically normal and motile sperm). Testicular ultrasonographic analysis revealed reduction of testicular volume and changes of testicular echotexture in treated animals, compatible with tissue degeneration, fibrosis, and calcification of testicular parenchyma on histologic examination. In conclusion, intratesticular administration of zinc gluconate associated with DMSO reduces reproductive potential which may lead to subfertility or infertility in dogs.

Evaluation of efficacy and safety of zinc gluconate associated with dimethyl sulphoxide for sexually mature canine males chemical neutering.

The aim of this research was to evaluate the efficacy of zinc gluconate associated with dimethyl sulphoxide (DMSO) for chemical neutering in canine males. Fifteen sexually mature male dogs were divided in two groups, named control and treated. An injection was administered to both testicles, at a concentration of 26.2 mg zinc gluconate per ml and 0.5% DMSO in the treated group (11 dogs). The control group was given injections of saline solution (four dogs). Clinical examination and blood collection for a haemogram were done both before and after drug injection. There were 12 spermograms performed to analyse sperm motility, sperm vigour, ejaculate volume, testicle size, pathology and sperm concentrations. Libido was also measured. An ultrasound examination and histopathology were performed at the end of the experiment. Dogs' libido after chemical injection was reduced by over 50%. The spermogram analysis showed final mean results of 14.54% for sperm motility, 0.72 of sperm vigour and 37,150 per million spermatozoa per millilitre, values considered below the necessary levels at which fertilization can occur. Ultrasound and histopathology analyses of testicles for the treated group revealed more intense injuries when compared with the control group, with compromised testicular parenchyma and a decrease of germ cell number leading to total atrophy, indicating that the treatment reduced the fertilizing potential of male dogs, promoting a possible subfertile status.