Factors Affecting Calving Rate to AI in Cows

A postal survey was carried out to determine the influence of certain factors on calving rate of spring-calving dairy cows in Ireland for 2 consecutive years. Only 44% responded to the survey in 1973 and 58% in 1974. The calving rate for 8,285 inseminations was 66%. There was no difference between years in calving rate. Most of the repeat oestrous periods occurred 17 to 24 days after AI (70%) or 37 to 45 days after AI (10%). The day of the week was not related to conception rate but significantly fewer inseminations were carried out on Sunday. Both the individual technician and bull were significantly related to conception rate. For individual technicians there was no correlation in calving rate following insemination in successive years. Use of semen from the same or from a different bull for a repeat insemination did not affect fertility. The limitations of the survey are discussed.