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Breeding from your favourite mare - to breed or not to breed?
by Liz Brown MA,VetMB, MRCVS

At this is the time of year attention is drawn towards the stud season and preparation of mares for breeding.

Before deciding whether to breed from your mare there are many factors that need to be taken into consideration. The aim of breeding should be to produce a sound healthy foal that is suitable for the purpose for which it will be used. Obviously there are many pitfalls that may be encountered along the way, otherwise we would all be breeding derby winners!

The first consideration is do you actually need to breed a foal? You need to have a clear idea of the purpose for which you are breeding the foal. If you are unlikely to keep it yourself then do you have someone else in mind that will want to take it on when it is older? If you are likely to sell the foal once it is old enough then it needs to be an attractive proposition for someone to purchase. A foal from your favourite mare may have sentimental value for you but this may not translate to the purchaser if there are no other attributes.

Secondly do you have access to suitable facilities? You will need a large foaling box and a safe paddock with post and rail fencing. Foaling can take place outside if the weather is suitable but you should have access to a dry and draught-free stable or barn for use at or after the birth if necessary. Once the foal is weaned it will need a separate turnout area away from the mare.

The next question is, is the mare a good candidate to breed from? A common mistake is to breed from a favourite mare that has had to be retired early through lameness or tendon problems, this is inadvisable as the foal may inherit a predisposition to develop these problems later in life. Ideally you should be breeding from a sound healthy mare that has many of the attributes you are looking for in your future foal. Obviously not all of these will be passed on but at least it is a good starting point. You are unlikely to breed a significantly larger horse from a small mare so it is unwise to put a pony mare to a much larger stallion in the hope that the children will have something to grow into when they are older. Your mare should have good conformation. Any conformational abnormalities present in the mare may be passed onto the foal, despite your choice of stallion. Mares with any serious conformational fault should not be bred from. Inheritable conformation defects can predispose to navicular disease, bone spavin, curb, carpal bone fracture and upward fixation of the patella. Clean straight limbs and good foot conformation and quality are desirable. Your veterinary surgeon will be able to advise you about any specific faults that concern you.

Behavioural characteristics of the foal may be genetic, acquired or a combination of both. Foal behaviour tends to mimic that of the dam to a greater degree than the stallion. Ideally your mare should be calm and easy to handle; this will give the foal confidence from an early stage that humans can be trusted.

Next the general health of your mare should be considered. Increased age is associated with a decrease in fertility, due to many factors such as anatomical changes in vaginal and perineal conformation, endometrial fibrosis or endocrine changes. However many older mares are still capable of conceiving and carrying a foal to term.

Good general body condition is important. Evidence suggests that only in mares with extreme weight loss or obesity would reproductive potential be markedly affected. However for general well being you should keep your mare in normal condition, neither too thin nor too fat.

Pain and stress from laminitis, severe navicular disease, arthritis, old fractures and tendonitis may adversely affect cycling and reproductive efficiency. Advanced pregnancy involves greater weight and compounds painful effects of limb and joint disease. It is very unwise to breed from mares with such conditions.

Conditions such as chronic obstructive pulmonary disease with its accompanying cough can predispose to pneumovagina. Known cardiac disease, especially valvular insufficiencies, also may require management change or special attention. Your vet will be able to advise you on the significance of these conditions in your mare.

Teeth should be regularly inspected by your veterinary surgeon. A thorough inspection prior to breeding may highlight any early problems that might become more significant over the coming year. Weight loss, stress and pain can occur from problems that affect mastication. These include sharp edges, large hooks at the back of the mouth, malocclusions, missing teeth, wave mouth, root abscesses and occasional trauma with fractures. Sometimes a simple rasp is all that is required however heavy sedation is necessary to fully assess and treat some problems, other problems may require a full general anaesthetic. Obviously it is important to try to avoid this while the mare is pregnant so breeding may need to be deferred until potential problems are treated. Malocclusions such as over or undershot jaw (sow mouth and parrot mouth) have a hereditary component so mares or stallions with these defects should not be bred from.

Heavy burdens of parasites are commonly associated with weight loss, poor body condition and occasionally more severe clinical symptoms. An effective worming regimen should be used before, during and after pregnancy.

The conformation of the perineum and vulva of the mare is important for fertility and conception. This is the area you can see just by lifting up the tail, but does include deeper structures which can be assessed by your vet. For optimal perineal conformation the right and left vulval lips should meet evenly and appear full and firm, functioning as a seal and forming the first protective barrier between the external environment and the uterus. The vulval lips should be in a vertical position with a slope of no more than 10 degrees from vertical. Variations in perineal conformation include lengthening and sloping of the vulva forwards and sinking of the anus. Abnormal perineal conformation can lead to sucking of air into the vagina (pneumovagina) and problems such as cervicitis, endometritis, and subfertility. This can have many causes and is inherent in some mares. A flat croup, elevated tail set, underdeveloped vulval lips, and sunken anus all contribute to faulty perineal conformation.

Poor physical condition intensifies the problem and can lead to abnormal structure even in mares with normal conformation; as the muscles deteriorate the anus sinks farther forward and the vulva shifts from its vertical position to a more horizontal orientation. As mares age the effective length of the vulva increases. Trauma from previous foalings or from external factors can result in damage to the vulval seal.

A Caslick's operation is a simple surgical procedure whereby the edges of the vulva are cut and sewn together at the top to create a better seal and prevent air being sucked into the vagina. This can enhance the fertility of some mares with poor conformation. The use of the Caslick operation may perpetuate conformational faults by enabling mares to become pregnant that otherwise would be unable to conceive.

A normal healthy udder is necessary for the mare to lactate and feed the foal. Any hard lumps or abnormal swellings should be checked by your vet. These may indicate a previous episode of mastitis, which may have left scarring, rendering the gland non-functional for milk production.

Previous breeding records, if they are available, are useful as an indicator of problems that may recur. Factors such as previous reproductive surgery, previous history of uterine infection or treatment, early embryonic death or abortion may affect conception or pregnancy maintenance.

The following conditions should also be considered.

Hyperadrenocorticism also known as pituitary adenoma or cushings can affect reproductive potential. This condition usually occurs in older mares over 13 years, symptoms can include a long hair coat, often curly, that persists into the summer months, weight loss, excessive sweating, laminitis or excessive drinking.

Melanomas are tumours seen in some older grey horses, frequently observed round the anus, tail and perineal region as well as the head, neck and skin. They are unlikely to affect fertility unless they are extensive in the perineal region, however trauma during mating or foaling may precipitate growth and metastasis to internal lymph nodes or organs. Therefore it would be unwise to breed from a horse significantly affected by these tumours especially in the perineal region.

While there is no evidence to suggest that the tendency to develop sarcoids is heritable, sarcoids should still be carefully assessed before breeding from the mare. Sarcoids round the groin and udder region may confuse the foal and affect its ability to suckle. Many of the drugs or ointments used to treat sarcoids are unsuitable for use in pregnant mares, therefore treatment should be carried out prior to breeding.

The presence of any defects in the ventral abdominal wall or history of previous abdominal surgery such as for colic may pose a potential hazard to the pregnant mare.

Last but not least the cost of breeding a foal should be considered. The stallion fee is probably only a small percentage of the cost unless you are aiming to breed a derby winner. It is possible to breed a foal on the cheap without much veterinary input, however if you run into difficulties the bills can soon start to add up. Routine veterinary care would include a pre-breeding examination by your veterinary surgeon and the taking and testing of the necessary swabs and blood tests prior to going to stud. These will include swabs for contagious equine metritis (CEM), klebsiella and pseudomonas and may include a blood test for Equine Viral Arteritis (EVA). You should check directly with the stud as to their particular requirements and consult with your veterinary surgeon for advice on the appropriate times for these tests. Once at stud or the AI centre further veterinary costs include more swabs, scans and routine examinations. Further scans to confirm pregnancy and that the foal is developing normally will be carried out either at stud or by your veterinary surgeon. These routine costs will run into several hundred pounds.

If there are any minor hiccups along the way such as treatment for endometritis, caslick's operations or extra scans these will add to the cost. Vaccinations against Equine Herpes Virus need to be carried out in the 5th, 7th,and 9th months of pregnancy, revaccination for tetanus should be carried out 6 weeks prior to foaling. The foal and mare will need to be checked after the birth. As you will see breeding a foal is not a moneymaking exercise! If you have taken all the factors into consideration and decide to go ahead then good luck, but remember that your veterinary surgeon will be a very good source of advice especially if you are a first timer!

Anvil Vets:

Anvil Equine Veterinary Clinic, Tuckmans Farm, Copsale, Horsham, West Sussex RH13 7DL

Tel: 01403 731 213 Fax: 01403 733992

Email anvilvets@freeuk.com

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