Spring is in the air! In addition to the start of a new warm-weather trail riding season, in our barn that means two things: breeding and babies! This month we are going to take a closer look at breeding. Next month in anticipation of the foals expected at our farm this spring we will dive into babies.
BREEDING SEASON: It’s all about the ladies
Every spring the horses come back alive after the long winter. Reproduction is the strongest instinct and drive that horses have, even to the point that it takes precedence over eating
Mares are seasonally polyestrous, which means that they cycle (have hormone estrous cycles) many times per year (poly) but only during a breeding season (seasonally). Mares have a natural breeding season that is triggered by the increasing daylight in the spring. The light stimulates the receptors in the brain to produce reproductive hormones. These hormones are what control the regular periods of “heat,” or estrous in the mares. These cycles will continue throughout the summer and cease during the autumn as the days get shorter again.
The estrous cycles mares go through consist of days in which the mare will show estrus and be able to become pregnant, and days in which she will be in diestrus. While there is a lot of variation on the length of each cycle, most mares average 21 days from ovulation to ovulation. It takes several days for most egg follicles to mature and during most of this time the mare is not receptive to breeding. This time between heat cycles lasts on average 16 days. Once enough follicle growth occurs, a mare will start to show signs of heat for 3 to 8 days (on average 4-5). It is towards the last day of heat that the mare actually ovulates and therefore the best chance of breeding is on the last day of the heat.
Each mare is different about how they express their hormones. Other than showing obvious interest in stallions there are many signs that help you to tell if a mare is in heat.
Holding their tail elevated
“Winking” – opening and closing the lops of the vulva
“Squirting” of urine and mucus
Squatting
Lowered activity and seemingly stubborn behavior.
Impatient, anxious or preoccupied with something other than what you are doing with her.
Grouchy or downright mean (don’t judge ladies, I’ve seen many of you around the barn!)
While mares cycle through their heats in a regular pattern, veterinary therapies are also available to alter a mare’s estrous cycle once they are in season. Why would you want to alter a mare’s estrous cycle?
SAFETY: Some mares do not show their heats as clearly as others. Mares will only be receptive to the stallion and allow him to mount when they are in heat. Some mares may be in heat but not display any signs, causing breeders to miss the window for covering them. Other mares may be very flirtatious, showing all the signs, but not actually be in heat and therefore not being tolerant of the stallion mounting – which can be dangerous, particularly for the stallion.
LIVE COVER: Often, breeding is not done at home, meaning that the mare needs to be shipped off to another farm where the stallion lives. Veterinary therapies ensure that the mare will arrive ready to breed, so as to make the most use of the time the mare spends away from home and to save money on mare care fees during breeding.
ARTIFICIAL INSEMINATION: Timing is everything when using AI technologies. Once collected from the stallion, semen only has a short window that it can survive until being implanted in the mare. Ensuring the mare’s receptiveness is essential to the timing of the AI process.
Because light stimulates the heat cycles, it is possible to begin the breeding season earlier by artificially increasing the amount of light (i.e. – using electric lights in a stable). In order to work, lighting programs need to start 60 to 90 days before breeding and must be consistent, regular and controlled. Missing severally days in a row, just as leaving lights on 24 hours a day, could negate the effect. Most mares are put “under lights” for 16 hours of totally light perception per day. Why would you want to start the breeding season earlier?
INDUSTRY STANDARDS: The thoroughbred racing industry tries to produce foals as near as they can to January 1st (the official birthday of all thoroughbred race horses) as to ensure that the horse will be as mature as possible when it comes time to train and race.
FUTURITIES: Many futurity horses are bred as early in the season as possible to try to give the foal as much time as possible to mature so that by the fall the foal will be halter broke, shed its baby coat and be ready for the fall halter futurity competitions.
WORKING MOM: Competition mares may be bred early in order to ensure that they can compete throughout their early pregnancy and be given enough time after foaling to be brought back into training for competition the following year.
The most ideal conditions for foaling in most places in the United States are between May and July. This is when the most grass is available to help the mare’s milk supply and the temperatures are warm and comfortable for the foal.
A normal pregnancy in horses lasts roughly 11 months – around 340 days. As a result, most mares that aim at the natural birthing period are bred between June and August. It is common for mares to carry their foals a couple weeks longer, and on rare occasion for foals to be carried three to four weeks over time. Typically colts tend to be carried longer than fillies.
WHAT ABOUT THE BOYS:
While stallions also have a seasonal cycle in regard to their fertility, they are “on” virtually all of the time and ready and able to breed whenever there is a receptive mare. Because mare receptivity and fertility dictates breeding, stallions must be on call at all times to play their supporting role in the mating game.
Ironically, however, they are much easier to shut “off” than mares. Properly managed stallions, such as Sierra at Painted Bar Stables, will always be able to shut down and focus when not being required to breed. Most stallions will never attempt to breed a mare that is not in season. They may tentatively test the waters, but if the mare indicates that she is not interested they back right off. This “off switch” actually makes the stallions more easily trainable with regard to expressing their sexual behavior than mares, who are “off” part of the time and almost irresistibly “on” when their hormones are dictating them.
THE DIRTY DEED:
When you breed horses it is called “covering” a mare. In the horse world, there is nothing inherently private or intimate about breeding. To horses it’s just an important job that they take very seriously. Neither mares nor stallions are monogamous. While they do display preferences for individuals or “types” of individuals, copulation is not a representation of love but of worthiness. The mare’s goal is to find the strongest and most worthy stallion; the stallion’s job is to find as many mares willing to mate with him.
Types of breeding practices:
“Live cover” is the practice of having a mare mounted in person by a stallion. Typically the mare would be boarded at the stud’s barn of residence. While there, to determine the mare’s heat cycle she is “teased,” a practice of bringing a stallion that will or will not breed to her and presenting him to her over a barrier. When teasing, the handler looks at the reactions of the mare and the stallion (hostile, passive, attentive, displaying heat, etc…). A mare that is in heat will generally tolerate a teaser and may present herself to him, holding her tail to the side.
There are two methods for live cover: hand-held and pasture breeding. Both are exactly what they seem: hand-held breeding means that both the mare and the stallion are held by handlers on the ground with lead lines. In pasture breeding the mare is turned out in a pasture with the stallion several days to breed naturally. Hand-held is generally preferred, as it provides a cleaner environment and more opportunities for breeders to witness and ensure that the mare was covered and also places the handlers in a position to remove the horses from one another should they attempt to kick or bite.
Some registries, such as The Jockey Club that registers the thoroughbred industry in the United States, requires all registered foals to be bred through live cover to guarantee parentage and avoid fraud.
Artificial insemination is becoming increasingly popular as technology advances. Nowadays, AI has similar conception rate to live cover, but has several distinct advantages:
The mare and stallion never have to meet, reducing breeding accidents such as a mare kicking a stallion.
AI opens up the nation and the world to trans-national and international breeding, as semen can be shipped across continents to mares that would otherwise be unable to breed to a particular stallion.
A mare does not have to travel to the stallion, reducing the stress load for the mare and also making it easier to breed a mare that may have a foal at her side.
Because of AI collection, one stallion is able to breed to more mares as the ejaculate may be split between mares.
Frozen semen may be stored and used to breed mares even after the stallion is dead, allowing the lines to continue.
However, this does not mean that artificial insemination is without its difficulties. The first rule of semen collection is that everything kills semen – yes, everything. Even water kills semen. There are multiple fluids that are on the market to feed and nurture semen as it is stored, shipped and used for the breeding and it is important to find out exactly which one works best with the particular chemistry of each stallion.
Even when stored properly there is still difficulty. When using cooled semen, there is a small window of time that the semen can survive before it must be placed inside a mare requiring overnight shipping and tightly aligned windows for collection and the mare coming in heat. While frozen semen is becoming more and more popular because of longevity and ease, the semen of some stallions does not freeze well.
In order to have semen available to use for artificial insemination, a stallion is usually trained to mount a phantom mare although a live mare may be used. This process can be difficult for stallions to learn as it requires them to do something non-instinctual. To learn more about the phantom training process and to see how we taught Sierra to mount the phantom at Cornell University go to our previous blog post!
BREEDING CANDIDATES: Which horses to use
Fillies become sexually mature around 18 months old. While, in theory, they could foal as two-year olds, they are still growing at this age. Pregnancy takes a lot out of the mare in terms of nutrition and stress and could hinder the growth of a still maturing mare. As a result, most mares are not bred intentionally until they are four years of age (to foal at five years). Mares often can go on breeding until late in life and suffer no ill effects from it, especially if they have been bred regularly throughout their life. However, it can be more difficult to get an old mare pregnant for the first time late in life.
With colts, the decision is much more important: it’s not about when to breed, but whether to breed at all. There are very few colts (home-bred or from first-rate lines) that are good enough to use as stallions. With so many first-rate stallions available commercially, it is far better to use one of these for many reasons:
Because stallions will over time produce more progeny than any one mare, it is even more important that the stallion be worthy of the task: no conformation defects, genetically free of disease, and moreover a kind, calm and trainable personality. Few horses can claim to have all of these assets.
Young colts are difficult to handle and a probably better gelded, unless there is a specific reason for not doing so. Both colts and stallions require expert handling with the sort of skills that is ordinarily available only on studs. It is difficult, if not actually dangerous, for amateurs and is not to be recommended.
There’s a liability in owning a stallion that vastly outweighs that of any other horse. Because stallions are always “on” if a mare is willing, a loose stallion can be a huge liability for any stable resulting in damage and unwanted pregnancies. Beyond that, the presence of a stallion can be of great disruption to other horses causing unforeseen liabilities that come from beyond the reach of the stallion himself.
CHOOSING THE COMBO: Matching mares and stallions
The irony is that just because you have two great horses does not mean that they will make a good pair. Unfortunately there is no simple answer to which horses make a good match. The goal of any breeding is to have parents that complement one another. Factors to consider:
Function: What do you plan to do with the foal once you have it? This is the most important question to ask and needs to be answered and taken into consideration when evaluating the conformation and personality of any breeding sires and dams. Form to function is the backbone to understanding biomechanics.
Future Breeding: Will you plan on breeding the foal? It may be important to look at bloodlines and registries needed to make your foal a good breeding candidate.
Genetics: There are many genetic diseases that horses only display in homozygous form – meaning that both the stallion and the mare could be carriers. Knowing both a mare’s and a stallion’s genetics can ensure a healthy foal.
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Color: Color should always be the least important factor when breeding, however if all other factors fit, then it doesn’t hurt to look at what genetic possibilities there are for color!
As with anything, it is important to make a list of the horse’s strengths and weaknesses. Horses that share weaknesses should probably not be matched together. You want to make sure that the stallion will improve on the mare’s weak points and complement her type. Complementing is key; breeding together horses that are on extremes of a spectrum can also cause a variety of issues as well. For instance, if a mare has a very large and blocky head, it may not actually be a good idea to breed her to a stallion with a very small head because the result could not be an average, but a mix and match of features.
BABY IN THE OVEN: While the mare is pregnant
Time passes quickly once the mare is in foal. Throughout the pregnancy there are a couple key landmarks:
Month 5, 7 and 9: the mare receives a rhinopneumonitis vaccine to help prevent miscarriage.
Month 9-10: the mare should be vaccinated for tetanus, eastern and western encephalomyelitis, influenza, west nile and rabies. Vaccinating a pregnant mare is not only important to maintain her health, but also to provide protection for the foal once it is born. The horse does not transfer antibodies to the foal from the maternal blood supply during pregnancy; however, a mare will produce very thick milk called colostrums for the foal to drink immediately after birth. Colostrum from a properly vaccinated mare contains antibodies that will provide the foal with protection and immunity against diseases.
Other than that, nothing really changes that much until the end of the pregnancy. While the mare may need slightly more food, they should be kept at their usual weight. If the mare has inadequate feed, nutrients and water the foal may be aborted or miscarried because of stress on the mare’s system. Conversely, a fat mare is more likely to produce a foal with angular leg deformities and she will be much more prone to difficulty foaling.
Not only can you still ride mares while they are pregnant, riding can be an important component to the care of a pregnant mare. Many vets advocate for riding a pregnant mare up until the last month of pregnancy as it has health benefits for both the mare and the foal. Strong, healthy, physically fit mares will give birth to strong and healthy babies. And, fact of the matter is that pregnant mares work very well – especially since they will not be experiencing the ups and downs of being in heat.
That said, there are some important things to keep in mind while riding the pregnant mare:
Never add workload to a pregnant mare that was not in work prior to pregnancy.
As the pregnancy progresses the workload will diminish.
As the belly grows she will lose some of her bending abilities.
The saddle that once fit her may start to not fit anymore, especially closer to the end of pregnancy. At the end of the term bareback pads or simply bareback can be a comfortable solution for both the mare and the rider.
BREEDING DECISIONS: to breed or not to breed?
The biggest decision is not only which mare and stallion to select to produce the exact foal, but if you are up to the task! While the horses don’t have many problems in breeding, it is advisable for novices to think twice before putting their mares in foal. Caring for a pregnant mare and being prepared for the needs of a foal isn’t for the faint of heart. Birthing and rearing a foal means extra work, and demands special facilities, skills and experience.
This is one of the reasons that we at Painted Bar Stables strongly support our custom foal program. The custom foal program allows individuals to choose one of our mares here at Painted Bar Stables to breed to our amazing stallion. We'll breed the mare, care for her and walk her through her pregnancy, deliver the baby and take care of the foal before it's weaned and sent home to you. By the time you get your baby it will be healthy, registered, halter trained and well handled and ready for you to help it grow into an amazing adult. You'll be welcome to participate the entire time through the process.
