Porcine zona pellucida is a form of zona pellucida extracted from the ovaries of pigs, often referred to by the initials PZP. It is a popular source of antigens for immunocontraception.
The zona pellucida is a thick membrane that surrounds the unfertilised eggs of mammals. In order for an egg to be fertilised, sperm must first bind to, and then penetrate the zona pellucida. When porcine (pig) zona pellucida is injected into other mammals, antibodies are produced which attach to that animal's zona pellucida, preventing the sperm from attaching to the egg, therefore preventing fertilisation.
Porcine zona pellucida has been used in wildlife contraception since the late 1980s. Animals with which PZP has been employed in this context include elephants, feral horses, elk and whitetailed deer.