Putting Your Mare in Foal


There are two methods by which you may choose to cover your mare:
natural mating or artificial insemination (AI). Most mating management these days is driven by man’s desire to control the covering process so as to minimise any risk to valuable stock and man; minimise the number of coverings per mare per foal, and ensure a specific stallion covers a specific mare.


Natural mating is the natural physical act of covering a mare with a stallion. Within these practices vary greatly from the natural pasture breeding of wild ponies to the intensive ‘in-hand’ covering of very valuable stock.

Natural pasture breeding

In the wild, stallions run free with their harem of mares detecting whether or not they are in oestrus by examining them daily for signs of sexual acceptance. The process is leisurely and unrushed and the signals used are smell and taste rather than sight. Natural courtship may occur over several days as the mare slowly progresses from dioestrus into full oestrus, and takes place between a mare and stallion well known to each other. The mare will show that she is in full oestrus by standing still, relatively passive, curling her tail to one side, urinating, often bright yellow urine with a characteristic odour, or she may just take up the urinating stance. She will expose her clitoris (the area at the bottom of her vulva) by opening the lips of the vulva, this is termed ‘winking’. When she is fully in oestrus the
stallion will mate her.

If a mare is not in oestrus she will be aggressive to the stallion who will be unable to get closer to her than the initial advance. The stallion will then turn away transferring his attentions elsewhere, and return later that day or the next.

In the natural system a stallion will cover a mare up to 8–10 times in 24 hours. Nature’s system works extremely well resulting in high pregnancy rates per oestrus period. It is a system, however, which is rarely practised today, and is only occasionally seen in pony studs, or with horses run on large expanses of land with minimum involvement from man. One of the problems is that for such a system to run completely naturally the stallion will only cover the mares within his harem and no outside mares can be introduced solely for covering. This can cause difficulties as most studs require visiting mares to be covered by their stallions in order to increase the stud income. The introduction of outside mares in this type of ‘natural’ system can result in jealousy and hostility from mares within the system, and uncertainty between the stallion and the outside mares. Hence most studs control the covering of their own and visiting mares, often in an intensive, ‘in-hand’ mating system.

Mating in-hand

Close management of mating is practised on the vast majority of studs today, and is normally termed in-hand mating and involves the complete control of the events of covering. In this and in many other ways, we now control the life of the horse to such an extent that there is little similarity between their natural state and the way most horses now live.

Many studs separate their fillies and colts early on in their lives, sometimes from birth and often at weaning. In the ‘natural’ system colts and fillies run out together and interact with each other as part of a herd. Youngsters are disciplined by other members of the group and they learn respect at a young age when the chance of serious injury is reduced. One of the problems of intensive systems is that social interaction of young stallions with fillies and mares is removed. In-hand mating then expects stallions to cover mares that they do not know in the highly charged atmosphere of covering, it is not surprising therefore, that the risks of the mare rejecting the stallion and of injury to both parties are high. Many stallions are very valuable, worth tens or hundreds of thousands of pounds. All these issues lead to a very controlled covering process. In addition to this comes the problem of determining when a mare is in oestrus. In the natural system the stallion detects mares in oestrus by using smell and taste but humans have to rely on sight, that is, on observing the behaviour of the mare. This can prove inaccurate, hence most studs use a teaser stallion.


The teaser stallion is an entire stallion, often of low value, possibly a pony, used under controlled conditions to detect whether a mare is in oestrous or not, but he is not allowed to cover her. Once the teaser stallion has confirmed that the mare is in oestrus she can then be prepared and covered by the stallion of your choice. This means that the stallion used to cover the mares only goes near mares that are confirmed to be in oestrus and so greatly reduces the risk that he will be damaged by a dioestrus mare. Occasionally, less valuable stallions are used to tease the mares they will cover but, the close management of teasing means that they are still protected from damage.

There are problems associated with in-hand covering, the main one being that in their natural state courtship between the stallion and the mare is long but teasing is concentrated into a short period of time and forces the attentions of the stallion upon the mare. Some mares object to this even if they are in oestrus, and so it can be difficult to determine whether they are in oestrus or not. Problems are often encountered with mares with foals at foot. Such mares often object, occasionally violently, to the removal of the foal before teasing and covering, a practice normally done to protect the foal. In the natural system the foal stays close to the mare, but appears to know instinctively to keep its distance. Teasing some mares before feeding or turnout or if it is very hot, cold, raining, windy etc. can be inaccurate, as these conditions may upset the mares and make them reluctant to show oestrus. Some mares need a longer time to be teased, this can be a problem in a busy stud working to a tight schedule and they may never seem to be ready to cover. Again, some mares will only show oestrus under certain conditions, i.e. in the covering yard, when being washed ready for covering, tail bandaged, or when a twitch is applied. It is a good idea, therefore, to have detailed mare records and if you are aware that your mare shows some of these characteristics to let the stud owner/groom know before you have her covered.

There are a wide range of methods used to tease mares, depending on the stud, the value of the stock and the facilities available. In all of the methods the typical signs of oestrus, docility and acceptance of the stallion are looked for.

Veterinary examination

Veterinary examination, to confirm the stage of the mare’s oestrous cycle, is routinely used in many studs, especially when running valuable stallions so that their use can be optimised. Veterinary examination may be used alone, or as a back-up to teasing. There are three types of veterinary examination: ultrasonic scanning, rectal palpation, and vaginal examination. All three techniques are described above. They are used mainly to assess ovarian activity but also the appearance of the uterus, cervix and vagina in order to estimate the likely time of ovulation and therefore establish the best time to cover the mare.


Once it has been determined that the mare is in oestrus and is ready for covering both the mare and the stallion need to be prepared. The exact nature of the preparation will depend upon the system used for mating. Preparation ranges from the strict codes of practice seen in the thoroughbred industry to practically no preparation at all, which is often the case in many native pony studs. The most cautionary preparation will be discussed in the following account though you may find that the stud you choose dispenses with some, if not all, of these preparation techniques. Exact management practice also depends on the size of the stud, labour available etc. In larger studs, there are often two to three breeding sessions per day spaced at regular intervals e.g. 9.00 a.m., 2.00 p.m. and 7.00 p.m. Most mares are covered twice within anoestrus, at 24–48 hour intervals or until ovulation has been confirmed.

2- Alternative natural covering methods

As mentioned previously, there are many variations in covering practice. Many methods are cost-effective and used on the smaller native studs where nomination fees are cheaper, for example, native ponies successfully cover mares in-hand in a convenient field near to the main yard. This is how mares would have been covered in the past when stallions were walked from farm to farm. If covering is to occur in a large field then the stallion used must be well behaved and controlled, as his escape may cause serious problems with neighbouring mares.

Pasture breeding is another alternative, popular in South Africa and South America and also Iceland, where mares are run in large herds over wide expanses of land. In such systems, stallions are turned out to run free with a group of mares and to cover them at will. This system is the nearest to the natural situation but, as discussed presents problems with visiting mares. A ‘half-way house’ between in-hand breeding and pasture, breeding is to allow the stallion to be loose in the field and introduce mares to him individually, either restrained or free. This system allows the stallion to be used efficiently but allows visiting mares to be covered in a near-natural system. Stallions used in this system must be well behaved and, especially if the mare is restrained, their characteristics should be well known to the mare handler, so that any necessary avoiding action may be taken. Turning a stallion out with an individual mare is a popular method in native pony studs and can be used to get problem mares in foal.

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