Modified insemination procedure in cattle: deep uterine deposition of smaller numbers of frozen-thawed or sex-selected spermatozoa

SUMMARY After describing the site of fertilisation and that of the functional sperm reservoir in the female tract, proposals are made concerning a modified site of sperm deposition. A deep pre-ovulatory insemination into the ipsilateral uterine horn - the side adjoining the ovulatory follicle - should raise the chances of establishing viable spermatozoa in the isthmus where they would undergo storage. Suppressed motility within viscous secretions and binding of the head to endosalpingeal microvilli characterise this phase. Release and activation of such spermatozoa would be prompted by imminent ovulation and associated endocrine programming delivered via a local route. Potential advantages of deep insemination include (1) raising the overall fertility of genetically valuable bulls whose non-return rates are sub-optimal; (2) reducing the number of spermatozoa in each insemination dose; (3) using effectively the limited numbers of sex-selected sperm cells (X and Y chromosome bearing spermatozoa) currently available from flow cytometry; and (4) breeding from valuable but oligospermic bulls. Putative disadvantages might include (1) rectal palpation of the ovaries to locate the preovulatory follicle; (2) damage or even perforation of the uterine wall by the deep insemination catheter; (3) risk of polyspermic fertilisation; and (4) the inappropriateness of the technique for non-clinically qualified inseminators. Each of these reservations is responded to in a rational manner. In conclusion, a modified technique of insemination would be feasible under commercial conditions, might enable retention of genetically valuable bulls deemed of only average fertility under test conditions, and could give a welcome boost to a sagging artificial insemination industry.