How does GonaCon differ from PZP?
A. Porcine zona pellucida (PZP), another immunocontraceptive vaccine, has been used to sterilize dogs, coyotes, burros, wild horses, and white-tailed deer temporarily. The PZP vaccine, also known as SpayVac™, causes multiple estrus cycles in female deer. GonaCon, however, prevents female deer from entering estrus.