High deer densities increase vehicle collisions, damage agricultural crops, and amplify the spread of zoonotic and animal diseases, intensifying human-deer conflict. In addition, deer impact on forest vegetation can influence the distribution and abundance of other wildlife species. Greater demand for non-lethal means of animal damage control has led to an interest in contraception as a wildlife management tool. The development of a single-injection Gonadotropin-Releasing Hormone (GnRH) contraceptive vaccine by NWRC reduces logistical limitations and cost of using immunocontraception as compared to a vaccine that requires two injections. This study assessed the efficacy of two different GnRH-KLH (keyhole limpet hemocyanin) vaccine designs in a single-injection study, to determine if Mycobacterium avium bacterium in the adjuvant is necessary for the success of a single-injection contraceptive vaccine. Forty-two captive female black-tailed deer were divided into 3 groups. Control deer were injected with saline solution, one treatment group received GonaCon™ (a GnRH-KLH vaccine paired with AdjuVac™ adjuvant that contains a small quantity of killed M. avium bacterium), and the second treatment group received GnRH-KLH vaccine with DEAE-Dextran/oil as the adjuvant. Contraceptive success was evaluated by monitoring progesterone, pregnancy specific protein, antibodies to GnRH-KLH conjugate and to Johne’s bacterium (M. avium), and actual pregnancy rates. Pregnancy rates were significantly different based on treatment (X² = 9.389; df = 2; P = 0.009). Pregnancy rates in deer treated with GonaCon™ were significantly reduced as compared to saline controls (P = 0.006), but there was no significant difference between GnRH-DD compared to saline (P = 0.297). Significant difference was found between GonaCon™ and GnRH-DD (P = 0.055). Results suggest that M. avium in the AdjuVac™ adjuvant is essential for the success of the single-injection GnRH vaccine GonaCon™. The development of a single-injection vaccine will increase the practicality and lower the cost of using immunocontraception as a tool to control deer populations.