• contraception;
  • fertility control;
  • immunocontraception;
  • porcine zona pellucida


The biological efficacy of porcine zona pellucida (PZP) immunocontraception and the timing of booster inoculations were determined in 24 species of ungulates and five species of non-ungulates across 10 years of treatment and for which no technical problems were identified. The collective contraceptive efficacy for 265 ungulates, 25 bears, and 11 sea lions, across 517 contraceptive intervals was 93.3%, and contraceptive efficacy ranged from a low of 60% in nyala (Taurotragus angasi) to 100% in 16 other species. The timing of annual booster inoculations was adjusted, between 6 months and 12 months, depending on the length of the breeding season and the species-specific immune responses. The high degree of efficacy in bears and sea lions suggests that the PZP vaccine has some application in certain non-ungulate species. Technical problems in the timing and delivery of the vaccine can cause non-biological failures and were identified in an additional 20 animals, not included above, and included inoculating pregnant animals, the use of needles too short for effective intramuscular injections, failure to complete the initial inoculation series, and failure to give booster inoculations at the prescribed time. Zoo Biol 0:1–10, 2005. © 2005 Wiley-Liss, Inc.