Effects of Porcine Zona Pellucida (PZP) Vaccination With Spayvac® Using Three Different Adjuvants on Ovarian Activity in Mares

Introduction

Contraception can be provided to wild horses in a humane, economically feasible, and publicly acceptable manner. Currently, pZP immunocontraception has the greatest potential to control fertility because it is easy to administer, is safe, can provide multi-year efficacy, and has minimal side effects. SpayVac® (ImmunoVaccine Technologies, Inc. [IVT], Halifax, Canada) is the only single-dose pZP vaccine with proven multi-year contraceptive efficacy, which makes it practical and economical for broad-scale application in the field. Because the pZP antigen is a poor immunogen, vaccine effectiveness depends upon choice of adjuvant and formulation. The objective of this study was to compare the effect of vaccinating with pZP formulated as SpayVac® containing one of three adjuvants (proprietary IVT adjuvant, non-aqueous MFA [modified Freund’s adjuvant], and aqueous emulsion MFA) on ovarian activity in mares. Our hypothesis was that, irrespective of adjuvant, SpayVac® vaccination would not affect ovarian activity in mares. [...]