Horse Breeding Horse breeding refers to reproduction in horses, and particularly the human-directed process of planned mating of animals. While feral and wild horses breed successfully without human assistance, it can be beneficial to domesticated horses. Humans can increase the chances of conception, a successful pregnancy, and successful foaling.
The male parent of a horse, a stallion, is commonly known as the sire and the female parent, the mare, is called the dam. Both are genetically important, as each parent provides 50% of the genetic makeup of the ensuing offspring, called a foal. (Contrary to popular misuse, the word "colt" refers to a young male horse only.) Though many amateur horse owners may simply breed a family mare to a local stallion in order to produce a companion animal, most professional breeders use selective breeding to produce individuals of a given phenotype, or breed. Alternatively, a breeder could, using individuals of differing phenotypes, create a new breed with specific characteristics.
Some breeders consider the quality of the sire to be more important than the quality of the dam. However, other breeders maintain that the mare is the most important parent. Because stallions can produce far more offspring than mares, a single stallion can have a greater overall impact on a breed. However, the mare may have a greater influence on an individual foal because its physical characteristics influence the developing foal in the womb and the foal also learns habits from its dam when young.
Basic Horse Reproduction While horses in the wild mate and foal in mid- to late spring, many horses domestically bred for competitive purposes, especially horse racing and various futurities, are usually born as close to January first as possible, so as to be at an advantage in size and maturity when competing against other horses in the same age group.
A mare comes into estrus roughly once every month during the spring and summer. When an early foal is desired, barn managers will put the mare "under lights" by keeping the barn lights on in the winter to simulate a longer day, thus bringing the mare into estrus sooner than she would in nature. Mares signal estrus and ovulation by urination in the presence of a stallion, raising the tail and revealing the vulva. A stallion, approaching with a high head, will usually nicker, nip and nudge the mare, as well as sniff her urine to determine her readiness for mating.
Once fertilized, the egg goes on to the uterus, taking about seven days and already dividing. Upon entering the uterus, the egg might have already reached the blastocyst stage.
The gestation period lasts for about eleven months. During the early days of pregnancy, the embryo, or fetus, is mobile, moving about in the uterus until a protective membrane surrounds it, making it stationary. A heartbeat can be detected on day 21, and the fetus gender can be determined by day 70 of the gestation. Initially, the fetus is pinpoint size. Halfway through gestation the fetus is the size of between a rabbit and a beagle. The most dramatic fetus development occurs in the later trimesters.
Foaling A special foaling stall or shed that is large and clutter free provides the mare with a safe place to give birth. Most mares foal at night or early in the morning, and prefer to give birth alone when possible. Labor is rapid, often no more than 30 minutes, and from the time the feet of the foal appear to full delivery is often only about 15 to 20 minutes. Once the foal is born, the mare will lick the newborn foal to clean it and help blood circulation. In a very short time, the foal will attempt to stand and get milk from its mother. A foal should stand and nurse within the first hour of life.
To create a bond with her foal, the mare licks and nuzzles the foal, enabling her to distinguish hers from others. Some mares are aggressive when protecting their foals, and may attack other horses or unfamiliar humans that come near their newborns. Foals are typically weaned at 4-8 months of age, although in the wild a foal may nurse for a year.
After birth, a foal's navel is dipped in iodine to prevent infection, it is sometimes given an enema to help clear the meconium from its digestive tract, and the newborn is monitored to ensure that it stands and nurses without difficulty. While most horse births happen without complications, many owners have first aid supplies prepared and a veterinarian on call in case of a birthing emergency. People who supervise foaling also watch the mare to be sure that she passes the placenta in a timely fashion, and that it is complete with no fragments remaining in the uterus, where they could cause a serious infection. If the placenta is not removed from the stall after it is passed, a mare will often eat it, an instinct from the wild, where blood would attract predators.
Foaling Care Domestic mares require specific care and nutrition to ensure that they and their foals are healthy. Mares are given vaccinations against diseases such as the Rhinopneumonitis virus (which can cause abortions) as well as vaccines for other conditions that may occur in a given region of the world.
Mares are often fed more than other horses and are provided supplemental vitamins and minerals because their bodies require extra nutrition to form and nurse a foal. Many feeds designed for pregnant and lactating mares also have extra fat and protein.
Deciding To Breed A Mare Breeding a horse should be taken seriously, and the owner should be willing to invest the time and money into the endeavor. It is agreed by most that the one area where an owner should not cut costs is the stud fee, which is generally the area in which most amateur breeders try to save money. If a mare owner is not financially able to breed without cutting back on the stud fee, it is often best to wait to breed the mare.
A mare should not be bred for the sake of it, but instead have valuable qualities to pass on. The mare owner should in an honest and in an unbiased manner consider the mare’s temperament, conformation, performance record, soundness, bloodlines, and health. Only a mare of good quality should be bred. Many times a mare is bred out of the owner's love for her, rather than because she is of good quality, producing a disappointing and unathletic foal. The mare owner has a great responsibility in this aspect.
Mare owners should also recognize the fact that they will probably not make a profit off their breeding. Top breeding farms know where to cut costs, and are producing in bulk, so are better able to make a profit. The average mare owner, however, should generally aim to break even.
Choosing A Stallion The stallion should be chosen to complement the mare, improving on her poorer qualities. A bad crossing between two otherwise superb horses may produce an average foal. However, a good crossing between two above average horses can result in a very nice foal.
Generally, the stallion should have proven himself in the discipline or sport the mare owner wishes to breed for. An owner intending the foal for jumping, therefore, should not breed the mare to a cutting horse or a local backyard stallion that has not competed.
Bloodlines are often considered when choosing a stallion, as some bloodlines are known to cross well with others. If the stallion has not yet proven himself in the breeding shed or while competing, the bloodlines of the horse are often a good indicator of his quality and possible strengths and weaknesses. Some bloodlines are known not only for their athletic ability, but could also carry a conformational or genetic defect, poor temperament, or for a medical problem. Some bloodlines are also fashionable or otherwise marketable, which is an important consideration should the mare owner wish to sell the foal.
The mare owner should consider the size of the stallion. Though most foals adapt in the womb to the size of the mare, on occasion, a mare crossed on a much larger stallion could have foaling problems if the foal is particularly large. Size may also affect the intended use of a foal. A large horse is often preferred for show jumping and eventing, while smaller animals are often considered better cutting and reining horses. If the breeder intends the horse to be used as a child's mount, it is generally advisable to breed for a smaller animal rather than a larger one.
Temperament is often a critical factor to consider when choosing a stallion. This is especially true if the mare owner is intending to breed a horse for a child or amateur, as a good temperament is often a top priority by nonprofessional horse owners. Poor temperament may also be detrimental to performance when the horse competes, if it is constantly fighting the requests of the rider. Conversely, horse racing can favor horses that are aggressive because they tend to intimidate their opponents while running, and many "mean" racehorses have been excellent on the track.
The conformation of both parents is of utmost importance. Conformation is easily passed on, and poor conformation may ruin a foal’s chance of ever succeeding in his intended discipline. One parent should have especially strong conformation in the areas where the other is weak. So a mare with slightly crooked legs but a powerful hind end might cross well with a stallion with exceptionally straight and well-conformed legs, but a weaker hind end.
The fertility of the stallion should be noted, including the motility of his sperm if he is to be bred using AI. A stallion may not be able to breed naturally, or old age may decrease his performance. Mare care boarding fees and semen collection fees can be a major cost, and if the mare does not conceive, these costs cannot be recovered, even if a stud fee is refunded. It is important not to assume that a stallion with a good competitive performance career is a fertile stallion: the great racehorse Cigar was infertile despite his fantastic career on the track. A mare owner should ask the stud to supply the stallion’s breeding statistics, including the number of mares that he bred and the number that were actually impregnated.
The offspring, or “get,” of a stallion are often excellent indicators of his ability to pass on his characteristics, and the particular traits he actually passes on. Some stallions sire fillies of great abilities but not colts. Secretariat was known as a broodmare-sire: his sons and daughters for the most part did not perform particularly well (with Risen Star and Lady's Secret as notable exceptions), but many of the offspring of his daughters had talent (interestingly, his greatest racing daughter, Lady's Secret, was a major disappointment as a broodmare). Some stallions are fantastic performers but never produce offspring that win in their sport, though their offspring may succeed in another discipline. For example the racehorse Babamist produced offspring that excelled in the sport horse disciplines, especially eventing, but never succeeded on the track.
A purebred horse is often worth more than a horse of mixed breeding, though this matters more in some disciplines than others. The breed of the horse is usually secondary when breeding for a sport horse, but some disciplines prefer a certain breed of horse, such as American Quarter Horses for reining and stock horse events. Sometimes, purebred bloodlines are an absolute requirement: Racehorses in the United States must be registered to race.
Covering The Mare There are two general ways to "cover" or breed the mare:Live cover: the mare is brought to the stallion's residence and is covered "live" in the breeding shed. She may also be turned out in a pasture with the stallion for several days to breed naturally. The former situation is often preferred, as it provides a more controlled environment, allowing the breeder to ensure that the mare was covered, and places the handlers in a position to remove the horses from one another should one attempt to kick or bite the other.
Artificial Insemination (AI): the mare is inseminated by a veterinarian, using either fresh cooled or frozen semen.
After the mare is bred or artificially inseminated, she is checked 16 days later to see if she “took”, and is pregnant. A second check is usually performed at 28 days. If the mare is not pregnant, she may be bred again during her next cycle.
Live cover
When breeding live cover, the mare is usually boarded at the stud. She is "teased" several times with a stallion that will not breed to her, usually with the stallion being presented to the mare over a barrier. Her reaction to the teaser, whether hostile or passive, is noted. A mare that is in heat will generally tolerate a teaser (although this is not always the case), and may present herself to him, holding her tail to the side. A veterinarian may also determine if the mare is ready to be bred, by ultrasound or palpating daily to determine if ovulation has occurred.
When it has been determined that the mare is ready, both the mare and intended stud will be cleaned. The mare will then be presented to the stallion, usually with one handler controlling the mare and one or more handlers in charge of the stallion. Multiple handlers are preferred, as the mare and stallion can be easily separated should there be any trouble.
The Thoroughbred industry requires all registered foals to be bred through live cover. Artificial fertility treatments, listed below, are not permitted.
By contrast, the standardbred industry allows registered foals to be bred by live cover, or by artificial insemination (AI) with fresh or frozen (not dried) semen. No other artificial fertility treatment is allowed. In addition, foals bred via AI may only be registered if the stallion's sperm was collected during his lifetime, and used no later than the calendar year of his death or castration
Artificial Insemination
Horse semen being collected for use in artificial insemination.Artificial insemination (AI) has several advantages over live cover, and has a very similar conception rate:
The mare and stallion never have to come in contact with each other, which therefore reduces breeding accidents, such as the mare kicking the stallion.
AI opens up the world to international breeding, as semen may be shipped across continents to mares that would otherwise be unable to breed to a particular stallion.
A mare also does not have to travel to the stallion, so the process is less stressful on her, and if she already has a foal, the foal does not have to travel.
AI allows more mares to be bred from one stallion, as the ejaculate may be split between mares.
AI reduces the chance of spreading sexually transmitted diseases between mare and stallion.
AI allows mares or stallions with health issues, such as sore hocks which may prevent a stallion from mounting, to continue to breed.
Frozen semen may be stored and used to breed mares even after the stallion is dead, allowing his lines to continue. However, the semen of some stallions does not freeze well, and live cover is sometimes the only option. Also, as noted earlier with respect to standardbreds, a particular breed registry may ban the use of frozen semen in posthumous breeding.
A stallion is usually trained to mount a phantom mare, although a live mare may be used, and he is collected using an artificial vagina (AV), which is often heated to simulate the vagina of the mare. The AV has a filter and collection area at one end to collect the semen, which is then processed in a lab. The semen is then chilled or frozen and shipped to the mare owner. When the mare is in heat, a veterinarian introduces the semen directly into her via a syringe and pipette.
