VET’S DIARY: Artificial insemination increases in mares

We have seen an increase in the number of mares being presented for AI recently as owners realise they can get their mare in foal without sending her to stud.

The internet has made high-quality stallions readily available from the UK, Europe and beyond by overnight delivery of chilled semen for insemination within 24 hours of collection. Fairmoor Equine Clinic is a BEVA-approved AI premises with two vets registered to perform AI.

Older mares are being presented for AI once their career finishes. However, their fertility is reducing with age. Pregnancy rates decrease with age as mares become more susceptible to early embryonic death. We medicate these mares after insemination in an attempt to maintain the pregnancy.

Ultrasound scanning allows close examination of the uterus and ovaries and assessment of the stage of the cycle as well as picking up abnormalities which may prevent pregnancy or need treatment to enhance the chances of success. Uterine cysts may be detected as these are more common in mares over 14 years old.

If the mare is not cycling, that can be a problem, but drugs are available to bring them into season in some cases.

A breeding soundness examination should be carried out by your vet to assess the mare’s likely breeding potential. Due to advances in ultrasound scanning, prediction of the time of ovulation is more accurate which enables a single insemination of chilled or frozen semen to be used to achieve a pregnancy. This is beneficial as fewer inseminations cause less insult to the uterus as well as maximising the chances of successful fertilisation.

Scanning is done post insemination to check for ovulation and fluid. Older maiden mares are more prone to fluid in the uterus after insemination due to a tight cervix.

The fluid will prevent implantation in the uterus. However flushing after insemination for up to five days will remove any inflammatory material through the cervix and combined with a Caslicks procedure will limit infection and enhance the chances of pregnancy. We have had good results with AI using these techniques.

A 14-day pregnancy scan is recommended and this is the best time to detect twins as they can be managed at this time by removing one. Twins are not viable because the placenta cannot sustain twins and will lead to complications such as difficulty foaling, retained placenta, reduced fertility when rebreeding the mare, abortion or birth of dead or weak foals. A follow-up scan at 23 days for a foetal heartbeat confirms the survival of the remaining embryo. Drugs to enhance the survival of the pregnancy can again be used.

Late pregnancy monitoring is becoming more routine in order to detect pregnancy complications early and in some cases abortion can be avoided. Modern ultrasound scanners enables easier imaging of the deeper abdomen allowing the foetal size, foetal heartbeat and the placenta to be assessed. Monitoring is recommended in an older mare to make sure the foetus and placenta are healthy especially if any of the following are seen, running milk, vaginal discharge, colic, swollen abdomen or any illness during pregnancy.

Embryo transfer is becoming more popular among competition mare owners. The process involves inseminating a mare then flushing out the embryos and transferring them into a recipient mare. This allows mares to produce foals while continuing to perform up to the highest level and allows breeding more than one foal per mare per year. Unsound mares or older mares with problems such as pregnancy loss or weak abdomens may be able to donate an embryo but not carry the pregnancy themselves. This is an exciting alternative to breeding after the end of the athletic career although the extra cost is significant.