Live Cover Breeding of Horses: Pros & Cons of Natural Service

Live Cover
Pasture Breeding
In-Hand Breeding
Disease Prevention

Natural service, or live cover, is a common breeding method in the horse industry in which a stallion and mare physically mate. This method is relatively inexpensive and requires less personnel involvement than artificial insemination.

Breeders can choose between pasture breeding and in-hand breeding as natural service options for their breeding program. Many breeders opt for pasture breeding due to the low cost and minimal requirement for horse handling.

For high-value horses, in-hand breeding is more common, as it reduces risk of injury to the mare and stallion. However, this method requires significant personnel training for the procedure to be safe for both horses and humans. Working with people experienced in the procedure is crucial for a good outcome.

Natural service increases the risk of venereal disease transmission, requiring breeders to be strict about testing protocols prior to using a horse in their program. The most common venereal diseases in horses are contagious equine metritis, equine viral arteritis, equine coital exanthema, and dourine.

Each of these diseases requires specific management and testing to reduce the risk of disease transmission in a live cover breeding program.

Live Cover Breeding of Horses

Live cover breeding refers to the natural process where a stallion and mare are brought together to mate without any Assisted Reproductive Techniques (ART). It contrasts with artificial insemination, where semen is collected from the stallion and then introduced into the mare’s uterus.

Natural service is one of the most common methods of breeding used in the horse industry. In fact, some breeds, such as Thoroughbreds, require all foals to be born from live cover methods, rather than artificial insemination.

Additionally, natural service programs are often cheaper and require less veterinary involvement than artificial insemination programs.

The two main types of natural service are pasture breeding and in-hand breeding, each of which have their own advantages and disadvantages.

Advantages and Disadvantages

Breeders must consider the advantages and disadvantages of natural service compared to more expensive or more complicated options, such as artificial insemination. Depending on their personal goals, the value of the horses involved, and breed requirements, one may be more advantageous than the other.

Advantages of Live Cover:

General advantages of natural service over artificial insemination techniques include: ^[1]^[2]

Reduced management of mares for monitoring their estrus cycle
Do not need to train the stallion to a breeding dummy for semen collection
Ability to register the foals in registries that require live cover only, such as the Jockey Club for Thoroughbreds

Disadvantages of Live Cover:

General disadvantages of natural service include: ^[1]^[2]^[3]

Increased risk of injury for both the stallion and mare
Possibility of spreading venereal disease through sexual contact
Both the mare and stallion must be in the same location for breeding to occur

Pasture Breeding

Pasture breeding typically involves turning one stallion out with a pasture of 15 – 20 mares. ^[1] Most breeders choose to turn out the breeding mare group 1 – 2 weeks prior to introducing the stallion, so that the mares can establish a social hierarchy. ^[1]

Breeders may choose to check their mares for pregnancy once they pull the stallion from the herd, however many simply wait to see which mares produce foals during the following year. ^[1]

Compared to in-hand breeding, pasture breeding has several advantages, including: ^[1]

Little to no horse handling required
Reduced costs from both reduced horse handling and not having to closely track mares’ estrus cycles

Disadvantages of pasture breeding include: ^[1]

Risk of injury to the stallion or the mares due to unsupervised breeding
Cannot identify fertility problems in either the stallion or mares until the breeding period has concluded
Cannot identify an accurate conception date to determine the mare’s due date

Pen Breeding

Pen breeding is a variation of the more traditional pasture breeding method, but is conducted within a smaller, confined space, typically a pen or corral. The primary purpose of pen breeding is to allow for a more controlled environment than a large pasture, while still allowing the horses to mate naturally.

In pen breeding, a single stallion is introduced to a mare in estrus within a pen. The pen must be free of hazards and have secure fencing.

The advantages of pen breeding include: ^[7]

Easier for breeders to closely monitor the horses
Potential to intervene in case of aggressive behaviour
Shorter duration as the mare and stallion are put only together during her estrus cycle
Easier to ensure mating occurs within a specific timeframe
Requires less space for breeders with limited pasture

However, pen breeding also has several disadvantages including:

Less room for the mare to move away if the stallion becomes aggressive and vice versa
Less efficient as the stallion is only with one mare at a time
Constant supervision is important to ensure the safety of both horses
Not suitable for particularly aggressive horses

In-Hand Breeding

In-hand breeding, also known as controlled breeding, is particularly common for high-value horses, as it reduces the risk of injury to the stallion and the mare. However, in-hand breeding involves considerably more management compared to pasture breeding.

Instead of letting the horses mate freely in a pasture or enclosure, they are brought together under controlled conditions with handlers present to ensure the safety of both horses.

The major benefit of in-hand breeding is reduced risk of injury to the horses. Other benefits include: ^[1]

A precise breeding date is known for estimating the mare’s due date
Stallion semen evaluation is possible by collecting a dismount sample after breeding
Ability to properly clean the mare’s perineum and the stallion’s penis prior to breeding

Disadvantages primarily relate to the increased management and personnel involvement required for in-hand breeding. In-hand breeding management requirements include: ^[1]

Maintenance of a “teaser” stallion to identify when mares are receptive to breeding
Repeated teasing of mares using the teaser stallion
Repeated rectal palpations or ultrasound examinations of the mare’s ovaries to determine optimum time for breeding
Participation of at least three trained individuals during the in-hand breeding process

Restraint and Protective Equipment

In-hand breeding requires appropriate restraint of both the mare and stallion to reduce the risk of injury. Many breeding operations use a chain lead shank and/or twitch to restrain the mare during the procedure. ^[1]

To prevent the mare from kicking at the stallion, some operations use a leg strap wrapped around one of the mare’s front limbs or breeding hobbles. ^[1]

Other equipment may include kick boots, which pad the mare’s hooves to reduce injury if she kicks, and a leather neck apron, which prevents injury to the mare by the stallion. ^[1]^[2] Some mares require sedation to facilitate breeding. ^[1]^[4]

For the stallion, the handler often uses a chain lead shank or breeding bridle for control. ^[1]^[2]

Stallions receive training to ensure that they lead well, stop, and back up on command prior to breeding. ^[2] This training reduces the risk of the stallion becoming out of control during breeding, which puts both the mare and handlers at risk. ^[2]

Stallions that rear, strike, or bite at the mare or handler must be pulled from service and receive additional training to reduce the dangerous behaviour. ^[2]

With stallions that only direct their aggression at handlers, changing the breeding shed configuration may yield effective results. By positioning the mare so only her rear end is exposed inside a stall in an indoor arena or other area with good footing that can be closed off, then turning the stallion loose to breed may lead to successful cover without incident. Stallions are easiest to handle right after breeding.

Handlers

The safety of the handlers is also paramount, particularly for those in direct contact with the stallion. All individuals involved in the breeding process should wear a helmet, equestrian safety vest, and work boots. ^[1]

At least three personnel are required: ^[1]^[2]^[4]

One to handle the stallion
One to handle the mare
One to direct the stallion into the mare if necessary

Only qualified individuals should be present in the breeding area while horses are present.

Breeding Location

The breeding area must be safe for both the stallion and mare to reduce the risk of injury. The floor of the breeding area should be non-slip and dust-free. ^[2]^[4] Many breeding facilities use synthetic or rubber flooring to provide adequate traction in their breeding area. ^[2]^[4]

The area should be as uncluttered as possible, to prevent horses from becoming entangled in objects. ^[4]

Individual stallions may have preferences on the footing type, and some stallions may prefer to breed “uphill” rather than on a flat surface. ^[2] The relative height of the stallion and mare can also play a role in adjusting the breeding location.

Mats can be placed behind a mare to give a shorter stallion easier access for breeding, or they can be placed under a mare’s hind feet to make her taller for a taller stallion. ^[2]

Breeding Procedure

The first step of in-hand breeding is introducing the mare to a teaser stallion, to ensure that she is in heat and receptive to breeding. Usually, breeding operations place mares in a padded stock during teasing, to reduce the risk of injury if the mare kicks or the teaser stallion strikes out. ^[1]

If the mare is in heat, the handler thoroughly cleans her perineum with soap in preparation for breeding to reduce the risk of bacterial contamination. ^[1] The handler then wraps her tail to prevent hairs from interfering with intromission. ^[1] The mare must be thoroughly rinsed as soaps/disinfectants are spermicidal.

Any restraints or protective equipment are placed, and a lubricant is added to the perineum to facilitate breeding. ^[1]

Handlers prepare the stallion next. The stallion’s penis is thoroughly washed prior to breeding, to reduce the risk of bacterial contamination of the mare’s reproductive tract. ^[1]^[3] An exception to this is stallion that are breeding regularly as this disrupts the normal bacterial flora of the penis ^[8]

Once both horses are prepared, handlers lead the stallion up to the flank of the mare, and allow him to interact with her. Once he is erect, the handlers allow him to mount the mare. One handler pulls the mare’s tail to the side, to prevent it from interfering with breeding. ^[1]^[2]

Once the stallion is finished, he should be immediately removed from the breeding shed to prevent aggression between the two horses. ^[1] The handler washes the stallion’s penis prior to returning him to his stall or paddock. ^[2]

Disease Prevention

The reproductive organs of both stallions and mares can harbour infectious bacteria, viruses or protozoa which can spread through sexual contact. ^[3] The risk of venereal infections is significantly higher for natural breeding, as antibiotics or other products used in semen extenders for artificial insemination can largely eliminate bacterial pathogens. ^[3]

Breeding operations often require disease testing to reduce the risk of spreading venereal infections.

Bacterial Endometritis

Although not a true infectious disease, the most common condition occurring after sexual contact in horses is bacterial endometritis. Endometritis, or inflammation of the uterine lining, typically occurs when bacteria that are naturally found on the perineum of mares or the penis of stallions enters the uterus during breeding. ^[3]

Endometritis can lead to infertility in mares, resulting in failed breeding and economic loss. ^[3] Common bacteria associated with bacterial endometritis include Streptococcus, Klebsiella, Pseudomonas and Escherichia coli. ^[3]

Thorough cleaning of the mare’s perineum and the stallion’s penis can reduce the risk of bacterial endometritis following breeding. ^[1]^[2]^[5]

Contagious Equine Metritis

Contagious equine metritis (CEM) is a bacterial infection with Taylorella equigenitalis. ^[2]^[5] The bacteria typically causes vaginal infections and temporary infertility in mares, with stallions showing few symptoms. ^[2]^[5] Some mares show no symptoms, and may be a source of infection for stallions. ^[5]

Both stallions and mares should be tested for CEM prior to breeding. To test for CEM, the veterinarian takes swabs of the clitoris and uterine lining in mares, or the penile shaft and prepuce in stallions. ^[2]^[5] A laboratory performs bacterial culture or PCR to identify the bacteria and confirm whether the horse is infected. ^[5]

Treatment of CEM involves antibiotics and thorough cleaning of the external genitalia. ^[2] Once the horse no longer tests positive for the disease, natural service can resume.

Equine Viral Arteritis

Equine viral arteritis (EVA) is a viral infection that causes damage to blood vessels, resulting in edema and swelling of the limbs and lower abdomen. ^[5] EVA may cause abortion or pregnancy loss in up to 60% of pregnant mares. ^[5]

Although EVA spread is primarily through respiratory secretions, it can also occur through venereal transmission through semen. ^[5] Diagnostic testing is recommended for all stallions entering a breeding program, as many horses show no symptoms of the disease. ^[2]

Typically, laboratory evaluation for EVA involves testing blood serum for antibodies against the virus, indicating prior exposure to the virus. ^[5] Stallions that test positive for EVA can still be used, but should only be bred to mares who have previously had EVA or have been vaccinated for the disease. ^[5]

As a preventative measure, young stallions that are not yet breeding can be vaccinated against EVA, which will prevent them from becoming an asymptomatic carrier. ^[2]

Equine coital exanthema

Equine coital exanthema is a viral infection caused by equine herpesvirus-3 (EHV-3). The infection is highly contagious, and causes small erosions or ulcers on the vulva or penis that resolve over 2-3 weeks. ^[5]

Once a horse is infected, EHV-3 remains latent in the horse’s reproductive tract. It may be reactivated at any point, causing another round of ulcerations of the reproductive tract. ^[5]

The main impact of EHV-3 for breeding operations is primarily due to loss of use of an affected stallion, which reduces the number of mares he is able to breed during the breeding season. ^[5]^[6] Mares are also at a disadvantage as they will miss breeding opportunities and may not become pregnant before the desired breeding window is complete. ^[5]

Prevention of EHV-3 primarily relies on thorough examination of breeding animals prior to breeding, so that actively affected animals are not bred and therefore do not spread the virus to other horses. ^[5]^[6]

Dourine

Dourine is a lethal protozoal disease caused by Trypanosoma equiperdum, and is primarily found in Africa, South and Central America, and the Middle East. ^[2]^[5] The exact transmission route of dourine is unknown, but is presumed to be venereal.

Dourine causes fever, discharge from the penis or vulva, and raised skin lesions, progressing to neurological disease and death. ^[2]^[5] Around 50% of horses die within 6-8 weeks of developing symptoms. ^[5]

Some horses appear to be asymptomatic carriers of the disease, so horses in areas where dourine is common should be tested for the protozoan prior to breeding. ^[5] Some international regulations require euthenasia of test-positive horses as part of an eradication strategy. ^[5]

Summary

The main forms of live cover include pasture breeding and in-hand breeding
Natural service has an increased risk of venereal disease transmission, requiring testing of animals prior to breeding
In-hand breeding can reduce the risk of injury to the mare and stallion, however this method requires extensive personnel involvement and training
The main venereally transmitted diseases in horses are contagious equine metritis, equine viral arteritis, equine coital exanthema, and dourine