Infertility and Embryonic Mortality in Female Rabbits Immunized with Different Sperm Preparations

Abstract

Female rabbits were immunized by multiple intradermal injections with washed ejaculated, epididymal or β-amylase treated rabbit sperm in Freund’s complete adjuvant emulsion. All treatments suppressed fertility, with only 2.3 percent of 364 eggs recovered from 17 immunized rabbits fertilized following intravaginal insemination, while the control fertilization rate was 95.7 percent. Reinsemination of females when immunity was declining showed that normal fertility was attained by about 25 weeks postimmunization. Intramuscular booster injections given to 5 does 61 weeks after initial immunization resulted in 47 percent of 19 eggs recovered being fertilized, compared to 96 percent fertilization in 26 eggs from 5 control animals. The very low fertilization rate in immunized females prevented tests for embryonic and fetal mortality when immunized animals were inseminated. In order to test whether the uterus of immunized rabbits was hostile to conceptuses, normal embryos were transferred to immunized females. The actual embryonic and fetal mortality appeared to be higher in immunized animals, but only the results for young born attained statistical significance (P<0.05). Collectively these results suggest that the infertility effect of immunization was primarily expressed as a block to fertilization.