Rethinking the role of GnRH-based immunization as a complementary tool for canine reproductive control

Canine reproductive control is a central component of humane dog population management, but its effectiveness depends on broader population, human-behavioral and governmental-level dynamics. Surgical sterilization remains the definitive and most widely used method for preventing reproduction in individual dogs; however, its population-level impact depends on whether programs can reach sufficient numbers of reproductively active animals with adequate timing, continuity and territorial access. In settings where surgical capacity is delayed, intermittent or limited, complementary non-surgical tools may help reduce the time during which dogs remain capable of reproducing. GnRH-based immunization is a biologically plausible approach that induces antibodies against gonadotropin-releasing hormone (GnRH), temporarily suppressing the hypothalamic-pituitary-gonadal axis and downstream reproductive function. This narrative review reconsiders the role of GnRH-based immunization in canine reproductive control, with emphasis on its biological basis, current evidence in dogs, operational interpretation and potential integration with surgical programs for canine reproductive control. Available evidence supports immunogenicity, endocrine effects and some reproductive and behavioral changes in dogs, especially in males, but uncertainties remain regarding individual variability, booster requirements, owner participation, field consistency, and population-level effectiveness. GnRH-based immunization should not be framed as a replacement for surgical sterilization, but as a complementary tool that may support context-responsive programs under specific population, territorial and programmatic conditions. Future studies should evaluate not only individual endocrine and reproductive outcomes, but also implementation feasibility, welfare, cost-effectiveness, owner participation, follow-up and long-term effects on reproduction at the population level.