Turning an active racing filly into breeding stock is not about sending an athlete into an easy, idle retirement. Rather, the transition from racehorse to broodmare marks the beginning of an entirely new and physically demanding career. For fillies, it means a change of handlers, daily routine, exercise, feed, and physique. For owners and breeders, it requires careful consideration and preparation.

Initial Steps for Transitioning a Filly to a Broodmare

Once the decision has been made to breed a filly, it is important to alert training staff. Most fillies will require weeks – if not months – to acclimatize to their new career, and since the breeding season occurs in late winter and early spring, it is often necessary to stop racing at the end of summer or at the beginning of fall.

Cutting back on intensive exercise can lessen the potential for severe injuries as well as allow for medical treatment of typical racehorse problems like soreness, breathing or digestive issues. It also means cycle-suppressors are no longer needed.

Many racing fillies receive estrus-suppressing medicines or procedures for various reasons. Before racetracks in North America banned the use of anabolic steroids in racehorses, it could take more than a year after a final dose for fillies to begin to have heat cycles. Currently, pharmaceuticals such as medroxyprogesterone acetate (Depo-Provera) or Regu-mate, or physical inhibitors like an intrauterine marble, are commonly used to either decrease the production of estrus-related hormones or to suspend the estrus cycle altogether. Normal estrus cycles usually take a few months to re-establish after physical or pharmaceutical suppression, so the sooner trainers know that breeding plans are in the offing the better.

Bear in mind as well that the average equine gestation period is 11 months and that the equine estrus cycle is directly impacted by light. In the dark months of winter, the estrus cycle of most mares goes through a rest period. But, in order to produce a foal near the optimal birthdate of Jan. 1, broodmares need to be impregnated sometime in February. This necessitates exposure to artificial light. Generally, it takes 60 days, or a minimum of eight to 10 weeks, under lights to achieve estrus activity. Thus, if a broodmare owner wants a foal on the ground around Jan. 1, 2020, the mare needs to be under lights by Dec. 1, 2018.

Finding A New Home

Immediately after leaving the racetrack, a mare should be kept in full or semi-quarantine in a stall away from other breeding stock for a few weeks to prevent the introduction of infectious disease. The newcomer’s shoes must be pulled for her safety as well as that of the other broodmares. An appropriate deworming schedule should begin, and any missing vaccinations should be given. A test for equine infectious anemia (EIA) is typically recommended during this period.

Once out of quarantine, a maiden mare is usually kept in a stall at night and turned out alone in a small paddock. Within a matter of days or weeks, one or two mares of similar age can be turned out together for short periods of time. The time outside can be incrementally increased until the turnout companions are introduced to the larger broodmare herd and kept outside either most of the day or all the time.

Gradual turnout is essential for transitioning racing fillies. Large, open pastures invite galloping and many ex-racehorses quickly become distressed or risk injury if suddenly let loose after the confinement and strict exercise regime of the track. Moreover, most racehorses are inexperienced at sharing turnout space with other horses, and racing fillies fresh of the track tend to exhibit far more energy and aggression than established broodmares like. While a little bit of bullying is common between herd members, physical attack and constant chasing away from food and water sources either on the part of older broodmares or a cocky newcomer must be prevented. All initial pasture interactions should be closely monitored.

Additionally, to reduce the stress of the transition on the overall health and reproductive viability of the horse, all personnel should be informed if a filly is a maiden. Stressed mares, particularly stressed maiden mares, will commonly fail to demonstrate a visible heat cycle and often act aggressively or fearfully with new pasture-mates and in the breeding shed.

Feeding a Broodmare

The optimal physical condition for a successful equine pregnancy is fit with a bit of fat. Mares in hard muscle don’t have the needed fat for conception and gestation, but mares with soft muscles tend to experience intense discomfort during the later stages of pregnancy and can have longer and more exhausting labour. Mares in poor or thin body condition tend to have more trouble conceiving and cannot provide the necessary nutrients for optimal fetal growth. Likewise, obese mares can also have trouble conceiving but their extra weight significantly increases the risk of developmental orthopedic diseases in their offspring.

Mares should be viewed and scored for body condition every week for several months after arriving at the breeding farm.

It is important to note that decreasing a horse’s exercise levels while increasing grazing aren’t guaranteed to add weight. This is particularly true for pregnant, or soon-to-be pregnant mares, pastured for long periods in cold or inclement weather. Additional forage, concentrated feeds, and vitamins and mineral supplements, may be needed depending on the weather, the location and the health of broodmare pastureland.

Reproductive Readiness

Prior to starting a broodmare career, a racing filly should undergo medical exams to determine her reproductive readiness. The conformation of the external genitals should be checked to ensure the lips of the vulva aren’t tilted or incline as this can cause urine to pool on the vaginal floor.

A quick surgical procedure called a Caslick’s suture can be done to prevent infections when this conformation fault is present.

The udder should also be checked for signs of injury to the teats, and the glands should be examined for signs of infection or scarring.

Internally, a rectal exam should be performed to determine the condition, size and placement of the ovaries, uterus, and cervix. Abnormalities like tumours or internal scarring can be ascertained, as can enlargement of any of the reproductive organs – an indication of bacterial or viral infection.

Many stallion farms require a uterine culture test to confirm a filly has no infections, and regular ultrasounds will likely be necessary to determine when follicle production is taking place and when the release of an egg is immanent.

Retraining Body and Mind

Maiden mares can readily be stressed by the demands of a broodmare such as frequent veterinary exams, transporting to stallion farms, labour pain. Even the actual breeding process of live cover can be extremely stressful, and occasionally dangerous.

A mare should be acclimatized to have her vulva washed and dried, and her udder manipulated without lifting a leg, kicking or biting. All broodmares must become familiar with ground restraints like twitches and halters and being handled around their heads and necks. It is particularly important that mares get used to the presence of unfamiliar people or horses touching their hindquarters. Desensitization through regular, full-body grooming and bathing can be beneficial.

Transporting a young mare to a stallion farm with a companion is a good strategy, although some breeding personnel prefer sedation if a mare is particularly agitated or resistant. Some type of restraint of the mare and stallion is common during live cover, but research has shown that mares are calmer and more receptive to breeding if they can spend time with a stallion or a teaser male. In fact, permanent stallion contact, such as a stallion housed at a broodmare farm, has been scientifically proven to increase conception rates.

It is an unfortunate truth that mares and stallions that do not appeal to one another, or that experience aggressive behaviour from handlers or horses during the live cover process, develop increasing behavioural problems during subsequent breeding seasons – even to the point of developing severe stress responses that require treatment or significant retraining.

It is also an unfortunate truth that not all mares are natural mothers. This is especially true of maiden mares. Although nursing releases endorphins that help a mare accept a new foal, the pain and stress of labour can cause a mare to reject her foal. Usually, most mares will adjust to motherhood within a few days and handling the udder before the foal’s arrival can help, but occasionally a mare will need to be restrained for nursing or kept separate from her foal until the pain of labour subsides.

It should be remembered that aggressive mares can physically harm the foals of other mares in pasture settings, while inattentive mares may not intervene when their foal is bullied by other mares or foals. It is important to observe the first pasture turnout of a new arrival and even limit the pasture size and pasture-mates of a new mother’s first turnout.

Combatting Boredom

Every year there are a handful of racing mares that are bred during the season that continue to race. This usually occurs if the mare is in the middle of a successful campaign and has valuable pedigree. It is a controversial practice because some people believe it is hard on the foal. However, there is no scientific evidence for this assumption.

Most racing fillies do adjust to their broodmare career, but there are some mares that don’t cope well without the excitement, activity, and attention they experienced at the racetrack. These mares often develop behavioural vices like cribbing, constant self-grooming or self-harm such as biting their flanks and legs. Some will pace stalls or fence lines, ram gates or charging handlers. A few will go off their food, drop weight or become listless and unresponsive. In such cases, if veterinary advisement concurs, consider light exercise under saddle, daily hand-walking or hand grazing. Brief turnout in busy areas of the farm can create some excitement and stimulate an ex-athlete’s mind.