Reproduction control in a feral feline population using an anti-GnRH vaccine.

This study aimed to evaluate the use of the Improvac® vaccine to avoid heat and pregnancies in queens and fertility in males during the breeding season. Twenty-eight intact animals were divided into treated males (G1, n = 7), treated females (G2, n = 18), and untreated males (G3, n = 3) that were untamed and could not be captured for immunization. In cats from the G1 group, the testicular volume (337.35 ± 95.74 mm) and testosterone concentration (1.31 ± 0.49 ng/mL) reached the lowest value 16 weeks after the first vaccination. At week 40, all queens exhibited both estrus cytology and estrus behavior, with serum estrogen (38.5 ± 1.93 pg/mL) and progesterone (0.5 ng/mL) concentrations within the physiological range for the phase. Eleven queens received a third dose of the vaccine at week 40, and none became pregnant by week 64. The remaining queens (n = 7) did not receive the third dose of the vaccine and became pregnant by week 44. In cats from the G1 and G2 groups, the hematologic parameters were within the physiological range for the species. The results of this study indicate that the Improvac® vaccine is safe and effective in the short to medium term in preventing cat reproduction.