The effects of active versus passive immunization of mares against inhibin on embryo quantity and quality

The aim of this research was to determine the effects of active verses passive immunization against inhibin in horses and in addition, to evaluate embryo morphology, quantity and quality between the two treatment groups and control group, along with evaluate body condition of the mares after treatments. In experiment 1, active immunization against inhibin resulted in an increase in ovulation rate through superovulation of these mares. Mares actively immunized against inhibin showed a marked increase in embryo numbers compared with control mares. The actively immunized group did show a reduction in body condition though, due to the abscesses and lesions at the injection sites compared with the control group who showed no reduction in body condition. In experiment 2, mares were passively immunized against inhibin, using purified and concentrated serum from one mare in experiment 1. This resulted in a higher than expected rise in embryo recovery rate over a shorter immunization period than in the actively immunized group, without the reduction in body condition as seen in actively immunized mares. Yet, the rise in embryo recovery rate was not as great in the passively immunized group as was in the actively immunized group. If this is due to a dose dependent reaction to the levels of the antibodies this may be overcome. As there was an increase in serum FSH concentrations. These results suggest that immunization against inhibin (both active and passive) can be used to increase ovulation rate in mares. This research, however, does not rule out other methods of superovulation that were not tested in this study, but is favorable of passive immunization against inhibin as a useful tool to accomplish it.