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Inseminating mares with chilled semen is a common method of reproduction, allowing owners to keep their mare at home and increasing the range of stallions available.

The aim of breeding using chilled semen has always been to inseminate the mare just before ovulation (when the mare’s egg is released).

But occasionally mares do not ovulate as expected or there may be problems with the courier service transporting the semen.

As a result, it has previously been thought that, because of a high incidence of both pregnancy failure and infection associated with inseminating the sperm after ovulation, the only option was to miss this breeding cycle and wait for the whole process of lining the mare up for insemination to start again. This was both costly and time-consuming.

Vets from a big breeding practice in the UK looked at the breeding records of over 150 mares inseminated with chilled semen.

They found that, contrary to opinion, good pregnancy rates with acceptable pregnancy losses can result from insemination with chilled semen within 16 hours of ovulation.

They did note that it was important the mare’s uterus was treated with saline flushing and an infusion of antibiotics after insemination to reduce the risk of her developing an infection.

Repeated administration of the reproductive hormone oxytocin was also given until the uterus appeared free from fluid.

This is extremely useful for all mare owners and vets working with chilled semen as it means we can often successfully inseminate the mare to obtain a viable pregnancy, even if the semen arrives late.

For the full veterinary article on what’s new in breeding, see the current issue of Horse & Hound (13 January, 2011)

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