WHEN IT comes to this time of year, owners of mares are faced with a myriad of options. It used to be much more straightforward... you chose a stallion, dispatched the mare to the stud where he was standing, and hoped she came back in foal.

WHEN IT comes to this time of year, owners of mares are faced with a myriad of options. It used to be much more straightforward... you chose a stallion, dispatched the mare to the stud where he was standing, and hoped she came back in foal.

Today, with the widespread use of artificial insemination (AI), there is so much more to consider. Do you go for natural service or AI? If it is to be AI, do you use frozen or chilled semen? Will you send the mare to an AI centre, or does your veterinary practice offer an AI service? If it does, can they scan and inseminate your mare at home?

My views on the various options available to mare owners are outlined in this article, along with advice on pre-breeding checks. Next month I will take a look at a vet's involvement with mares at stud, describe pregnancy diagnosis and how we deal with twins and problem mares.

Whether to go for natural service or AI will, to a large extent, be determined by the choice of stallion. Most Thoroughbred stallions only cover mares naturally because Weatherbys - the organisation that records all Throughbred matings and births in Great Britain and Ireland - will not accept foals borns by AI, embryo transfer or any other artificial means.

By contrast the majority of Warmblood and sports horse stallions are only available using AI since they combine stud and competition duties. Semen is also available from an increasing number of other stallions, including those of pony breeds and Clydesdales, for AI.

If you do have a choice between natural covering and AI, which should you use? The answer is not straight forward and is determined by several factors, which include likelihood of success, cost and convenience.

ULTRASOUND SCAN showing a large follicle on an ovary

LARGE CYST in a horn of the uterus. This is sufficiently large to reduce the chances of the mare becoming pregnant

It is a long-held and false assumption that a mare is more likely to conceive when covered by a stallion, rather than undergoing AI. Average overall conception rates - which are the percentage of mares that become pregnant over the stud season - are very similar at 75% for AI compared with 80% for natural service.

There is, however, a subtle difference in the conception rate per oestrus cycle between natural covering and AI, which is more significant for frozen semen. Recent data from the Thoroughbred industry showed that 65% of covered mares conceive per cycle. This compares with per cycle conception rates of 55-70% for AI with chilled semen and 35-50% for AI using frozen semen.

These figures indicate that, although overall conception rates are similar, it may take more attempts to get your mare in foal when using AI. This is especially true with frozen semen and should be factored into your budgetary considerations.

Natural service is not without its drawbacks and dangers. It usually means travelling your mare, possibly with foal at foot, to the stallion with associated expense. There is also the potential for physical injury and transmission of disease during covering. These risks should be mitigated by ensuring that the stud adheres to the appropriate health checks and that it is proficient in working with stallions.

An advantage of AI is that it can be done either at home or at a stud, veterinary practice or AI centre nearby. At home AI is only possible using chilled semen, since frozen semen requires careful handling and defrosting in a controlled environment. Chilled semen can be delivered to your home from most parts of Europe using next day couriers, and brings the prospect of using a range of non-UK stallions.

In some instances, chilled semen might only be available in the early part of the stud season. Many stallion owners prefer not to mix stud and competition duties and so will only provide frozen semen once the event, show jumping or dressage season gets underway.

One of the major costs of AI is the ultrasound scans required to coordinate insemination with the time of ovulation. This tends to be more intensive when using frozen semen, since the short lifespan of defrosted sperm requires pinpoint accuracy in the timing of insemination.

Mares will typically be scanned five times per oestrus cycle when using chilled semen and as many as 15 times when using frozen semen. Many studs offer so-called veterinary packages' so that you can budget your mare's vet bill.

By means of example, we charge £180 per cycle for all routine veterinary examinations and drugs when using chilled semen, and £245 for frozen semen using a fixed-time insemination protocol. The five-star' technique for frozen semen involves scanning the mare every six hours - including at midnight and 6am - for several days when she is in season and our fee for this is £595.

The best conception rates with frozen semen are achieved when the semen is introduced directly into the tip of uterus at the point where the egg enters from the ovary. This ensures that a high number of sperm remain viable and is done either using an endoscope or, as is more commonly the case, by guiding a long catheter through the cervix and into the appropriate horn of the uterus.

When looking at veterinary fees you should ask whether the packages include visit fees to the stud, the drugs required to bring the mare into season and induce ovulation, pregnancy diagnosis at 14-16 days and 28-36 days, and any non-routine procedures such as wash-outs and twin reduction.

Stud fees have never been cheaper than they are this year and studs are going out of their way to offer deals and incentives to mare owners. When looking at their prices, check their policy on returns for mares not in foal and whether there are additional fees for the collection and dispatch of semen for AI. You will also have to pay to have the chiller sent back to the stud.

In terms of budget, I suggest planning on two cycles for chilled semen and three for frozen. You can reduce your livery costs by taking the mare home once she has been confirmed in foal at around 16 days, and then either return her for the second pregnancy scan or have your own vet do that.

The final, and perhaps most important, way to ensure that your financial outlay results in a pregnancy is to be sure that your mare is reproductively healthy before she goes to stud. Your vet should examine her vulval conformation and perform a speculum examination of the cervix to check for infection or structural abnormalities that may affect her fertility.

The uterus and ovaries should also be examined by ultrasound to check for cysts, or any sign of infection or inflammation. In the case of mares that failed to conceive last year, it is well worth taking a swab and a biopsy from the uterus to see if there is underlying disease or damage that is causing infertility.

Thoroughbred studs require that your mare is tested for infectious causes of infertility, usually contagious equine metritis, equine viral arteritis and equine infectious anaemia. There is no similar statutory requirement for mares undergoing AI but some studs and centres do wisely ask that mares are also tested for these diseases since they can be transferred by AI too.