Effect of number and frequency of inseminations on fertility of mares.

This research study looked at the effect of the number and frequency of inseminations on the fertility rates of mares over a 10-year period. The data showed a higher rate of pregnancy in mares that are inseminated more frequently and those with a longer duration of oestrus.

Methodology

• The data was collected from 257 normally cyclic mares over a 10-year period.
• The study observed the relationship between the number of inseminations per cycle, duration of oestrus, and pregnancy rate.
• Mares were inseminated on alternate days of oestrus with 100 X 10(6) progressively motile spermatozoa.

Findings

• Mares that became pregnant were inseminated more frequently per cycle than mares that did not become pregnant. Specifically, the average was 3.4 inseminations per cycle for pregnant mares versus 2.8 for non-pregnant mares.
• The study found that the pregnancy rates increased with the increasing number of inseminations per cycle. First-cycle pregnancy rates ranging from 22.2% for one insemination to 58.3% for five inseminations and slightly decreased to 52.2% for six or more inseminations.
• The duration of oestrus – the period when the mare is receptive for breeding – was longer in mares that became pregnant compared to those that did not. The average was 7.9 days for pregnant mares and 6.4 days for non-pregnant mares.
• Mares that had an initial oestrus of less than 10 days had lower overall pregnancy rates (after three cycles) compared to mares with a longer oestrus period. First-cycle pregnancy rates were higher for mares inseminated more frequently per cycle.

Conclusion

• The study concluded that a higher number of inseminations per cycle and a longer duration of oestrus led to a higher pregnancy rate in mares.
• It also indicated that numerous inseminations per cycle in mares with prolonged oestrus periods were not harmful to their fertility.