Insemination strategy based on ovulation prediction in dairy cattle

Calving rates after first insemination are often less than 50% in practice. Part of this low percentage might be explained by wrongly timed inseminations. Our hypothesis is that it is better to time insemination according to ovulation instead of according to behavioral estrus, but up to now it has not been possible to predict the time of ovulation in practice. So, to better time inseminations in practice, there is a need for predictors of ovulation time. Therefore, the relationship between various estrus characteristics and time of ovulation was studied to investigate whether these characteristics could predict time of ovulation. First standing heat was displayed 26.4+/-5.2h before ovulation. The increase in number of steps during estrus predicted the time of ovulation (29.3+/-3.9h) best. The next question was: What is the best time for insemination relative to ovulation? When this time is known, an insemination strategy can be formulated. It was found that inseminations performed 24 to 12h before ovulation resulted in the highest number of good quality embryos at Day 7. This means that the optimal strategy is to inseminate 5 to 17h after the first increase in the number of steps. This strategy will result in optimal timed inseminations relative to time of ovulation.