Induced infertility in cattle by iso-immunization with semen and testis.

Iso-immunization of heifers with bull semen and homogenized testis combined with Freund's complete adjuvant resulted in an induced temporary infertility. Eleven heifers injected intradermally with semen and six heifers with testis required an average of4\m=.\11 and 4\m=.\83 inseminations/conception, respectively, compared with nine control heifers which averaged 1\m=.\11services/conception. Two heifers immunized with semen were slaughtered after eight and twelve unsuccessful inseminations, and an unfertilized ovum was recovered from each animal. Intra-uterine injection of semen and adjuvant caused nine heifers to require an average of 2\m=.\67services/conception compared with an average of 1\m=.\0for four control animals that had received intra-uterine injections of adjuvant and saline or adjuvant and rabbit semen. Four diagnosed pregnancies of the iso-immunized heifers underwent degeneration and an additional seven incidences of embryo loss were suspected from delays in return to oestrus after breeding. There was no evidence of embryo mortality in the control animals. Specific sperm agglutinins were detected in the serum and uterine and vaginal secretions of the iso-immunized heifers. The fertility of a particular insemination appears to have been negatively associated with the