Consequences of variation in interval from insemination to ovulation on fertilization in pigs

This review describes effects of variation in the interval between insemination and ovulation on the fertilization process in the sow. Inseminations performed too early or too late relative to ovulation decrease litter size and especially farrowing rate. This effect can be explained to a large extent by the increase in the percentage of non-fertilized eggs, resulting in partial fertilization or no fertilization at all. No effects of variation in the interval from insemination to ovulation are found on the percentage of degenerate embryos. Only moderate effects are found on mean embryonic development and variation in embryonic development at day 5 after insemination. In general, insemination between 0 and 24 h before ovulation gives good fertilization results. Factors influencing the optimal interval from insemination to ovulation, such as number of sperm cells used for insemination, storage time of liquid semen and use of frozen semen, and sow factors such as parity and breed are discussed.