Tower Equine

Veterinary Surgeons


Artificial Insemination - "Foals from the Freezer" - January 2008

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Getting a mare in foal used to be easy.

Mare 9 months in foal

The choice of stallion came down to how far you were prepared to drive, and the whole process was reassuringly natural. You took your mare to the stud, the stallion did his bit three or four times and eleven months later you woke up to the patter of tiny hooves............

These days it is a lot less simple. Artificial insemination with chilled or frozen semen has opened up a whole new freezer cabinet of possibilities, and your mares’ next suitor could come from anywhere in the world. But with choice comes uncertainty. What to choose? Chilled or frozen semen? A foreign stallion or one from the UK? How much will it all cost, and what is the likelihood of success? For the answers, read on.

Artificial insemination has several advantages over natural service. The chief one is increased choice of stallion, but AI can also cut down on travelling and stud costs, and reduce the spread of disease. It is also safer for both the mare and stallion. There can be downsides too. Veterinary costs can be a bit higher, and paradoxically, uncertified semen could increase the risk of disease.

But what about results I hear you ask? Well the good news is that pregnancy rates with chilled and frozen semen can be at least as high as with natural service. For certain mares they can even be higher. Remember however, that whichever approach you use, not all mares will get in foal on the first attempt. Breeding a foal is not like booking in for the farrier! You need to be prepared for at least a couple of tries. Above all bear in mind that artificial insemination is a group effort. Like a royal marriage there are three players in the game - the mare, the stallion and the vet. Each of these needs to do his or her job properly if you are to end up with a foal. So let’s look at each of these in turn.

The mare

By her mid teens, a mare’s likelihood of getting in foal is going down each year. This is common sense. Fertility declines with age. What is less commonly known is that older mares who have not bred will be less fertile than those who have. This is because the equine uterus ages faster when it isn’t being used. A fifteen year old mare who has had five foals will probably get in foal quite easily, but a fifteen year old first time breeder is likely to be tricky. Yet every week owners ring up saying ‘now that my mare is too old to compete, I want to have a foal from her’. This is a recipe for delays and disappointment. You may be fortunate – last season we had three polo ponies all in their late teens who all went in foal to frozen semen at the first go – but don’t risk it. Breed early. Whether you chose AI or natural service, the younger your mare, the better your chance.

The stallion

Not all Stallions are suitable for AI. For a start up to 30% have semen that simply does not freeze well enough. Unfortunately this doesn’t always stop stallion owners from trying, with the result that some frozen semen is of dubious quality. It is very depressing to spend time and money getting a mare all set up, and then to receive a sample of low motility semen No matter how fertile your mare, if the sperm are all on crutches, you won’t get a foal.

So choose a stallion with proven AI results. Most stallion collection centres will give you an honest opinion on the quality of a particular stallion’s chilled or frozen semen. Foreign stallions can be less easy to judge. Then there is the added problem of semen delivery. Chilled semen needs to be inside the mare in 24 hours – overnight delivery is possible from Europe, but courier services don’t work the weekend, making the timing of insemination doubly tricky. For this reason frozen semen may be a better option.

The vet

Preparing a mare for artificial insemination is not rocket science, but it does require a trained stud vet; someone completely familiar with synchronising ovulation and insemination. Practice makes perfect, so choose a vet who is doing this on a regular basis. Don’t be shy of asking about his or her success rates, and ask about the fees as well. Many vets offer a fixed price package per breeding cycle, which can help you keep track of costs. Each mare is an individual - a good vet will talk you through all the options and advise on what is most suitable for you.

Roger Lee MA VetMB, CertEM(Stud) MRCVS