Many breed registries still require breeding be done by live cover--the stallion physically covers the mare. The actual mating process is an awesome spectacle, but can be dangerous to the mare, stallion, and handlers when done in hand-breeding situations. It involves the stallion mounting the mare, inserting his penis into the mare's vagina, and vigorously thrusting until he ejaculates, then dismounting. If mishaps occur, the mare may not become pregnant, or injuries (to mare, stallion, or farm personnel) might occur.

No one method for managing live cover breeding is foolproof. Handling of the mare and stallion should be individualized to minimize injury and optimize success.

Natural and In-Hand Breeding

There are two traditional types of natural breeding: Pasture mating and hand-mating. In the wild, horses breed in a relatively stable social group or harem.

Stallions in the wild will interact with a mare (and vice versa) for hours or even days before mating. Pasture mating most closely mimics breeding of wild, free-roaming horses (with some exceptions). In pasture breeding, the stallion is allowed to run with one or more mares in a field. The stallion is responsible for determining the readiness of each mare for mating (i.e., he is responsible for estrus detection). In general, once a stallion gains experience in pasture mating, he is unlikely to attempt to breed a mare that is not in estrus. Exceptions do occur, thus some mating-related injuries can follow.

Additionally, some stallions are quite aggressive in pasture mating situations, and mares and foals are at risk of injury. Due to the lack of control over this type of situation, pasture mating is rarely practiced in today's commercial horse breeding world. Nevertheless, there are quite a few producers still employing this method of mating, particularly since it reduces time and expense associated with estrus detection and the actual mating process.

Much more common is the type of live cover known as hand mating, which requires some form of restraint of the mare and stallion. The amount of restraint will vary according to individual circumstances, particularly the temperament of the mare.

There should be a special area where the mating takes place. This can be outdoors or indoors. When indoors, a breeding shed designed specifically for the process is usually used. This area should be large enough to allow ample free movement of horses and people, have no physical obstructions that interfere with safety, have no "blind" corners that entrap personnel or animals, and have a flooring that provides good footing. The ability to clean and disinfect flooring and minimize dust is needed for a breeding shed floor.

The domesticated stallion is severely restricted in his interaction with mares. The amount of interaction largely depends on the management conditions at the breeding farm. Usually, Thoroughbred breeding stallions are confined to a paddock or stall and do not have interaction with mares or other horses except during the teasing and mating process. Under this type of management, some stallions might become unruly.

In order to lesson these aggressive tendencies, the stallion should be exercised every day. He could be turned out in a paddock, ridden, or longed.

Warmblood or sport horse stallions frequently compete while being used for breeding.

Stallions should be housed in large, well-ventilated stalls with plenty of clean, fresh bedding. There should be no sharp points in the box on which the stallion could injure himself.

Man-Made Breeding Dates

Unfortunately, man has his own ideas of when mares should foal. Since the early 19th Century, when Jan. 1 was declared the official birth date for Thoroughbred foals--irrespective of their actual birth dates within that year--horse breeders have been plagued with problems attempting to breed mares in the winter and early spring.

For some breeds, notably the Thoroughbred, an operational breeding season exists from Feb. 15 until the first week of July. This man-made breeding season means that many breeders try to get mares in foal from the middle of February onward.

To some, it might not be clear why so much trouble is taken in trying to breed mares before they are in their most fertile period. The reasoning is that the two major racing breeds (Thoroughbreds and Standardbreds) and the majority of the breed societies use Jan. 1 as the official birth date of every foal born that year. Therefore, a foal born on Feb. 12 and a foal born May 12 both are considered a year old the following Jan. 1. When these horses are sold as yearlings, having those three extra months to mature can make a huge difference in the price brought at auction. Having these two horses compete against each other as 2-year-olds--or even 3-year-olds--would probably give an advantage to the older animal that has had more time to mature.

Artificial Lighting for Mares

Fortunately, something as simple as light can cause the mare to cycle earlier in the season. Putting a mare under lights is a very common means of getting her to cycle earlier in the year.

Experience has shown that 16 hours of light stimulus (artificial plus natural) is adequate. One means is to provide light from 7 a.m. until 11 p.m. The extra artificial light is best added at the end of the natural daylight period, and works by suppressing the release of a hormone called melatonin. An area of the brain known as the pineal gland produces this hormone. Melatonin affects release of gonadotrophin hormones involved in follicle production and ovulation.

The light in the box must be bright enough to stimulate hormone production. This means a 150-watt clear bulb in the middle of a box/stall that measures 13 feet by 13 feet (four meters by four meters). If a strip light is used, it should be about four feet long (1.3 meters) with a 40-watt bulb. Care should be taken to eliminate shadows, as they can prevent a good response. A practical method of checking that there is sufficient light is to see if it is easy to read a newspaper wherever you stand in the box.

There are two important points to note with putting a mare under lights:

1) Extra lighting must be begun early. Generally a minimum of eight to 10 weeks is needed before she is cycling normally, thus mares should be exposed to the lighting system by Dec. 1. This should start them cycling normally by Feb. 15. It is not good enough to decide to put a mare under lights and one week later expect the mare to begin cycling. This situation often happens when a mare arrives at stud and is not yet cycling. Unless she has already been under lights, you cannot expect her to begin cycling in a few days just because you put her under lights. Remember with lighting to plan ahead.

2) Mares should be in good body conditio and well-fed when they begin extra lighting. It is preferable to increase the mare's body condition, and this might mean extra feeding. It is also important that the mares are healthy, on an appropriate deworming program, and have had regular dental checks.

In aged mares, delayed initiation of normal cyclical ovarian activity might reduce the number of estrous cycles during the breeding season; therefore, it is particularly important to prevent poor body condition from occurring in such animals. Good management can prevent prolonged anestrus.


Teasing is a vital part of the operation of a breeding farm. Teasing is the use of a stallion to encourage a mare to show estrous behavior under controlled conditions. Most, but not all, mares in heat show signs such as leaning toward the stallion, raising their tails, squatting, "winking" (repeated eversion) of the clitoris, and urinating. Some mares might take several minutes before they show signs of being in heat.

At most breeding sheds, the mare will be presented to a teaser stallion that is different from the stallion used for mating. This is to ensure the mare is exhibiting strong signs of estrus before the mating process is attempted. If she is not exhibiting signs of estrus, or will not allow the teaser stallion to mount her, breeding shed personnel might refuse to mate her to protect the mating stallion and mare from injury. The mare is then usually restrained by a twitch. For quiet mares, this might be enough.

The mare's tail should be bandaged and the vulva washed and thoroughly dried. A bandaged tail prevents tail hairs from damaging the stallion's penis or rubbing the mare's vulva. It is important to only use water to wash the mare and stallion, as antiseptics can destroy the natural bacteria, allowing more dangerous bacteria to grow.

Other preparations might include:

  • Felt boots applied to the mare's hind legs to take the force out of a kick, but boots can be dangerous to put on and take off and some mares resent them.
  • Holding up one front leg, either by hand or using a special leg strap, which should be fitted with a quick-release mechanism.
  • Hind leg hobbles with side lines; they prevent kicking, but can be dangerous if the mare or stallion become entangled in them.
  • Administration of a sedative to the mare when a mare is difficult to handle because of nervousness associated with being separated from her foal or with being a maiden mare that is unfamiliar with the stallion and mating process.

There is no one set method of restraining the mare for breeding. As with many aspects of equine reproduction, it is important to remember that each mare is an individual and should be treated as such. Also, the body weight and size of the stallion must be appropriate to the size and physical development of the mare.

Your veterinarian should continue to monitor the mare's cycle by daily rectal and ultrasound examinations and/or teasing.

Natural Breeding: The Stallion

The stallion should be handled with a long lead shank, but care must be taken to avoid entanglement. Placement of a chain shank through the mouth, above the gums, or over the bridge of the nose is commonly practiced by stallion handlers.

A number of other methods of restraint are also available (i.e., ear twitches, hobbles) and preferred by some handlers. The goal is to employ the least restraint necessary to facilitate normal stallion behavior, yet ensure the stallion is maintained under control in the breeding shed.

Ideally, he should be allowed to approach the mare from the left side, then brought up to the mare's hindquarters once the mare is displaying signs of full acceptance for mating. He is allowed to smell, taste, and lightly nuzzle the mare. The stallion should not be allowed to mount the mare until he has a full erection.

The mare's tail should be held out of the way while the stallion mounts and inserts his penis into the mare's vagina. The penis might have to be guided into the vagina, but handling the penis should be avoided if possible.

Once the stallion has entered the mare, he should begin to thrust vigorously. You should confirm that the stallion ejaculates by observing tail movement (flagging) or better still, by placing your hand lightly under the penis and feeling the urethral pulses. (The urethra is the tube through which the sperm passes during ejaculation.)

A safe dismount and quick separation of stallion from mare is important for the safety of the animals and handlers. Mares often will take a "parting shot" at the stallion if not turned quickly with their hindquarters away from the stallion and personnel.

Take-Home Message

Live cover breeding can be difficult and dangerous for humans and animals. Trained personnel are essential. The first time you watch live cover, you might be surprised by how physical it appears. Making sure breeding happens safely and effectively is a job requiring an enormous amount of skill and experience. The team in the breeding shed is often the difference between a live foal and a mating that doesn't prove successful. Breeders should work with their veterinarians to ensure the mare is ready and able to breed, and that the stallion is manageable and fertile.

About the Author

Jonathan F. Pycock, B. Vet. Med, PhD, DESM, MRCVS

Jonathan F. Pycock, BVetMed, PhD, Dipl. ESM, MRCVS, operates Equine Reproductive Services, a first opinion and referral private equine practice based in Yorkshire, England. He has published many papers and book chapters on a variety of equine reproductive topics, and edited the book Equine Reproduction and Stud Medicine. His main interests include ultrasonography, breeding the problem mare, and artificial insemination. Currently, he is evaluating the use of oxytocin and depot oxytocin as a post-breeding treatment for mares.

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