VET’S DIARY: Pregnancy monitoring to ensure healthy foals

At this time of year we are in full swing with horse breeding, writes Stephen Bradley.

Pregnant mares are foaling and then getting back in foal again. We are heavily involved in all of this from assisting difficult foalings to looking after sick foals and then inseminating mares to get them pregnant again.

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

We can examine these mares at our clinic or at home. The internet has made high-quality stallions readily available from the UK and Europe. Using ultrasound scanning we can predict when a mare will ovulate, then order chilled semen by next day delivery for insemination within 24 hours of collection.

Pregnancy rates have also increased with AI as expertise has developed over the past 10 years.

Frozen semen can be shipped worldwide and can be ordered in advance for when the mare comes into season.

Frozen semen may involve lower numbers of sperm than fresh or chilled semen and has a shorter life of six hours, so for these reasons deep uterine insemination is used which involves placing the tip of the insemination catheter to the tip of the uterine horn next to the ovary from which the ovulation has occurred.

This enhances the chances of the egg being fertilised as the sperm are in position as the egg descends from the fallopian tube.

Due to advances in ultrasound scanning ability, 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.

An increasing number of older maiden sportshorse mares are being presented for AI after their competition career finishes but their fertility is reducing with age.

If they are not cycling, that is a problem but drugs are available to kick start the cycle and bring them into season in some cases.

Older mares are more prone to pooling fluid in the uterus. This fluid will interfere with implantation of the fertilised egg in the uterus.

However, washing out after insemination will remove any fluid and coupled with a Caslicks procedure will enhance the chances of pregnancy.

Similarly older mares are more susceptible to early embryonic death but there are drugs available which can be used after insemination to enhance embryo survival.

Twin pregnancies are quite common but never have a good outcome in the horse as the mares placenta isn’t big enough to support two foals and will unfortunately result in abortion of both foals.

A 14-day scan after insemination is the best time to detect twins and remove one allowing the survival of the remaining embryo.

If twins are detected later than 18 days, it is more difficult to deal with and often the pregnancy will have to be terminated.

We do pregnancy monitoring in late pregnancy to make sure the foal and placenta are healthy.

We have just invested in a new ultrasound scanner which enables easier imaging of the deep horse abdomen allowing the foetal size, foetal heart beat and the placenta to be assessed.

This can be done routinely or if there is a problem such as illness in the mare, vaginal discharge, running milk or swelling of the abdomen.

This alerts us to the possibility of a high-risk foal being born which will need extra attention and allows us to start treatment which just may prevent abortion.