Are lower fertility bulls necessarily less fertile? Proposals concerning insemination procedures.

This essay argues that current procedures of selection for high fertility bulls may overlook young males of potentially high fertility unless these are tested by modified procedures of insemination. Should this suggestion prove to be true, even if only for a small proportion of young bulls that would not previously have been retained as stud animals, then valuable production genes would be kept in the national herd. Modified procedures of introducing the sperm suspension might include (I) deep intra-uterine insemination, (II) insemination into the functional sperm reservoir in the Fallopian tube isthmus, (III) laparoscopic insemination close to the utero-tubal junction, (IV) intra-peritoneal insemination, (V) insemination under conditions of mild superovulation, and (VI) insemination with smooth muscle stimulants and/or sperm stimulating agents added to the suspension. (VII) The potential value of in vitro fertilization assays, such as the zona-free hamster oocyte sperm incorporation test, is also noted. Even if only one of these approaches were found to be fruitful, its impact could be of major significance for the cattle breeding industry.