Long-term effects of PZP immunization on reproduction in white-tailed deer.

A 6-year study was conducted to determine the long-term effects of porcine zona pellucida (PZP) vaccine on the immune and hormonal responses, and reproduction of the white-tailed deer. The first 2 years of active immunization resulted in an 89% reduction in fawning. Vaccination with PZP produced reversible infertility lasting 1-4 years. Infertility was directly related to immune titers to PZP. Doe fertility was restored when the antibody titer dropped to minimal levels, but following re-immunization, infertility was reestablished. Reduction in fawning throughout the 6-year study was 76%. It was also observed that immune responses among deer were variable, especially in the first year of treatment. Variability was also observed among deer for the duration of infertility following the initial vaccination.