Optimum Strategies in Artificial Insemination, with Emphasis on the Timing Relative to Ovulation and the Role of the Boar

Optimised insemination strategies on pig farms aim at reducing the number of inseminations, without reducing reproductive performance. At the moment, one insemination with good quality semen can result in good fertilisation results when insemination takes place in a 24 h period before ovulation. However, knowledge of this optimal period is not sufficient to limit the number of inseminations to only one in all sows, because the time of ovulation of sows can not be predicted within a 24 h range. Therefore, to optimise insemination strategies on farms, either the period during which one insemination leads to optimal fertilisation results must be increased and/or the prediction of ovulation time needs to be improved. Much work concerning the timing of insemination -relative to oestrus characteristics-and reproductive performance (litter size, farrowing rate) has been performed in the sixties and seventies. Since the early nineties, ultrasound has allowed assessment of the timing of ovulation in spontaneously ovulating sows. Since then, experiments have increased our knowledge on the timing of ovulation in sows relative to behavioural and physiological changes and on effects of insemination strategies on fertilisation. Besides the timing of insemination, also the circumstances around insemination are important for fertilisation chances. In this overview, also recent data on the role of boar presence on uterine motility are presented (Langendijk, 2001).