Artificial Insemination

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In order to produce a foal, natural service between a mare and stallion is not always suitable or available. Either the stallion is competing and the breeding season would interrupt his schedule, or the stallion is abroad and too far away to make natural service viable. In both circumstances owners may require the assistance of artificial insemination (AI).

Horse - Equine Artificial Insemination

Chilled or frozen AI?

In AI the semen is collected from the stallion, transported to a different location, and then inseminated into the reproductive organs of the mare at the appropriate time in her reproductive cycle.

In its natural state semen will only remain viable for a few hours and the heat of the environment with soon cause the sperm to die. For this reason semen needs to be either chilled or frozen and preservatives added to maintain its longevity. The time taken to transport the semen from stallion to mare usually decides whether chilling or freezing the semen is most suitable.

Chilled semen- Chilled semen involves refrigerating the semen immediately after collection, placing it into chiller packs and then transporting it either by post or manual collection. In this form the semen will be viable for 2-3 days which usually gives plenty of time for inseminating. The conception rates (chance of producing an embryo) are greater than for frozen semen. For this reason by choice we would always advise working with chilled over frozen semen.

Frozen semen- Once the semen has been collected from the stallion, the semen is separated and added to a preservative. It is then frozen and stored below freezing, usually in dry ice. The semen can then be transported great distances as long as it is kept frozen. Once arriving at its destination it can be defrosted, re-awakening the sperm and inseminated into the mare. Unfortunately the freezing and handling process slightly reduces the viability of the sperm and conception rates using frozen semen is slightly lower than for chilled semen.

What is involved if I want to get my mare into foal?

The process of Ai is split into 3 stages: pre-breeding, insemination, and post breeding.

Pre-breeding- Early in the year you hope to have your mare inseminated a pre-breeding check is advised. This will involve a full clinical exam of the horse and also an assessment of the reproductive organs by palpating them by hand through her rectum and scanning them with an ultrasound machine. This will highlight any abnormalities that may hinder reproductive suitability.

Insemination- Arrangements need to be made with the stallion owners so that semen is sent well in advance for frozen semen, or delivered in a suitable form on the day of insemination (e.g. via post) for chilled semen. Inseminating the semen needs to be performed at a specific time in the mare’s reproductive cycle around the time the egg ovulates (is released) from the ovary. This is during the time she is seen ‘in season’ but is more accurately assessed by a vet through ultrasound scans of the ovaries and uterus. For chilled AI this need to be done within 12-24 hours of ovulation. Whereas for frozen AI it needs to be done with 6 hours of ovulation. So in using frozen AI a greater number of scans are required both during day and night.

Post-breeding- 1 or 2 days after insemination, some mares react to the semen placed into the uterus. It is therefore necessary to scan the mare to assess the need to flush away any inflammatory fluid produced to encourage healthy embryo growth. Pregnancy scans can be performed at around 14 days and 28 days post insemination.

Horse - Equine Artificial Insemination

Is AI best performed at my yard or a vet clinic?

Ai is best performed at the clinic where stocks can be used to safely position the mare for scanning and inseminating. This is safest for the vets scanning but also reduces the risk of damaging the mare if she were to move. If owners prefer all procedures to be performed on yards, sedation may well be required if stocks are not available.

Due to the frequent scanning of mares involved in frozen AI (every 6 hours), all procedures need to be undertaken at the clinic.

Are there any potential problems with AI?

1) Due to the intensive nature of scanning and inseminating, the costs of AI are greater than in natural service.
2) AI increases the choice of stallions from around the world but also increases the risk of disease spread. These include Contagious Equine Metritis (CEM), Equine Viral Arteritis (EVA), and Equine Infectious Anaemia (EIA) which are more common abroad, particularly mainland Europe, than in the UK. These viruses are transported in the semen and can survive the chilling or freezing process. For this reason imported semen must undergo strict screening tests and documentation. This adds to the costs involved and can prevent insemination if the documentation is substandard.
3) Though every measure is taken to ensure the process of scanning and inseminating is performed safely there is a small risk of damaging the mare’s rectum. This can have serious consequences and be potentially fatal.

If you would like to know more about AI in your mare, then please ring Andrew Wallace at the clinic.

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