Should I Breed My Mare?

To breed or not to breed . . . .With apologies to William Shakespeare, that is a question that perplexes many mare owners and is one without a single, simple answer. The problem usually begins with ownership of a mare which fits our equestrian needs--trail riding, jumping, cutting, roping, dressage, horse trials, whatever. Perhaps she is a stellar performer, and we want to perpetuate the bloodline. Or perhaps she is a serious disappointment in our chosen discipline, and we don't know what else to do with her.

There are a number of factors that must be weighed in making the decision on whether to breed a particular mare.

At the outset, let it be said that I have raised foals for a number of years and intend to keep doing so. There is something captivating and even rejuvenating about the arrival of a foal in the spring, after months of anticipation. Watching them grow and mature into solid, sound, usable horses adds to the positive side of the equation.

That being said, not everyone should raise a foal, and not every mare should be bred. Included in the considerations are economics, quality of the mare, availability of proper facilities, and capability of the owner, to mention a few.

Considerations

Let's start with some basic questions that involve these concerns and others.

First, why do you want to raise a foal from a particular mare? If you wish to perpetuate a great bloodline, that is justification in itself. However, if you have a mare which has failed to reach your expectations and you don't know what else to do with her, that is definitely not justification for breeding.

The problem in the latter case is that you just might breed into the foal all of the characteristics that made the mare such a disappointment. If that turns out to be the situation, you have accomplished nothing except to compound your problem.

Next question. Are you prepared to have the mare out of service for a time? Under normal circumstances, you would cease using the mare for about three months before she foals, and for perhaps four to five months after parturition. This time can be shortened, but you have to expect that the mare will be of at least limited use to you for about half a year.

Do you have an appropriate facility for the birthing process itself and later for the foal and its dam to obtain exercise? One does not need an elaborate, heated stable for the mare-in-waiting, but one has to be prepared with appropriate housing if the need arises. What this means is that you should at least have a sheltered run pen or shed. A barn with a box stall is best, of course.

It is true that many mares can foal with ease out in a pasture, but there is always the chance that this will not be a normal birth, and you should be prepared for that. If a veterinarian is called on to assist with the birthing because of dystocia, for example, it is far better to have the mare in a confined area.

Then, too, there is the matter of weather. Mares don't always pick the warmest or clearest day or evening to give birth. Sometimes it is in the middle of a rainstorm or snowstorm.

I remember the story of a friend who had a mare which foaled early. She was outside in a paddock. In the center was a large pile of manure waiting to be spread on the fields in drier weather. The night the mare decided to foal, there was a torrential rainstorm, with the paddock covered with mucky water. The only place the mare could find where she could be above the water was on top of the manure pile. It was there that she delivered what turned out to be a very healthy filly--a youngster that would grow up one day to be one of my riding horses.

That story had a happy ending, but what if that manure pile hadn't been there? It is possible that the foal would have been unable to rise on the slippery ground and might even have drowned. Then, too, there is the matter of the manure pile not being the most sanitary place for a birth. A wide variety of bacteria lurked in that manure, ready to invade the foal's system through its umbilical stump. A far cry from a stall bedded with dry straw and someone standing by with a bottle of iodine.

If the foal is to be born outdoors, the birth should take place on green grass.

Mares And Foals

Still another question. Have you had any experience in handling a mare at foaling time? Vast experience, of course, is not a requirement, especially if you have a veterinarian on call in case of trouble. However, you should know, for example, that a mare's birth canal muscle structure is so powerful that the fetus is expelled in a matter of minutes after she goes into labor. Cows might be in labor for a long period of time, often with no serious consequence to the calf. Not so with horses.

The entire sequence that starts with labor and ends in birth might last no more than 20 minutes. That leaves one with a very small window of opportunity to do something about dystocia and saving the foal, as well as the mare. That is not a time to procrastinate in seeking professional help, and you should know at least the basics of how to deal with the mare while waiting for the vet to arrive.

Your best ally before the birth is your vet. If you are short on knowledge and hands-on experience, quiz him or her in depth about potential problems and how to respond to them. And do it well in advance of the birth.

There is also the matter of how to handle the foal immediately after birth. Are you going to imprint it? If so, learn what this involves. Study and be prepared.

What if you aren't there for the birth and have lost the window of opportunity to imprint? Do you know how to handle a foal safely so that neither of you gets hurt? There is a great deal of information out there in the equine world about foals and their handling. You should avail yourself of the opportunity to learn before you are faced with the challenge of, for example, teaching the foal to lead.

The question regarding proper facilities extends to pastures and paddocks. Are the fences secure and safe? Drooping barbed wire fences are an invitation to disaster for inquisitive foals.

Your Herd

Then, too, there is the matter of other horses in the same paddock or pasture. They can be a help, or they can be a hindrance.

This spring, one of our veteran mares foaled out in the pasture. With her were a mare which had already foaled (that birth took place in a box stall) and another mare which we thought was pregnant, but turned out to be open.

In the early morning light, we saw the foal struggle to its feet and start nosing around for the milk supply. The dam was an old pro at this and stood still while the foal tottered and wobbled at her side.

However, at this point the mare without a foal moved in and cut the foal away from its mother. This confused the foal's dam and she began turning in circles in an effort to locate her offspring. Cleverly, the thieving mare kept her body between the colt and dam and began pushing the youngster away from its mother.

We quickly intervened, catching the mare that was attempting to steal the foal and removing her from the pasture. However, if we hadn't been there, it is very likely that the foal would have been prevented from nursing and would have missed out on ingesting the all-important colostrum that provides it with life-saving antibodies. Had this scenario been played out without human intervention, the foal could have died.

Geldings, too, have been known to steal foals. It might not happen frequently, but it has happened often enough that you should be aware of the possibility. The best of all worlds is that mare and foal have a paddock or pasture to themselves for a few days so that the bonding process will be rock-solid and complete. After that, they can be phased in with other horses, although you still should be on the alert for adult horses that might seek to "steal" the offspring or harm it.

There have been cases where adult horses have taken a dim view of a youngster being admitted to the band and have attempted to bite or kick it. Obviously, this can result in serious injury to the foal. When that possibility raises its head, either the mare-foal combination or the offending horse must be removed from the herd.

Still another question involves economics. Is it cheaper to raise a foal than to buy a horse which already has been trained? Maybe yes, maybe no. On the one hand, a horse which has been trained to be proficient in a given discipline might be very expensive when compared to what it costs to get a live foal on the ground. However, getting the foal born is only the beginning. It is a matter of at least a couple of years, and often more, before that youngster reaches a state of maturity where it can demonstrate its prowess. Along the way there will be training bills, vet bills, farrier bills, and the possibility that the horse will never reach its potential because of injury. There are many cases where that proven, expensive horse turns out to be the better bargain.

Like Mama, Like Baby?

Another question to be considered involves temperament. If the mare is mean and hard to handle, or nervous and flighty, there is a good chance that her foal will be the same. Not only does the mare have the potential to pass on these qualities genetically, she might reinforce them with her own behavior. The foal is tightly bonded to its dam during the first weeks and even months of its life, and often mimics the mare's behavior patterns.

Conformation also is important. Does the mare have good conformation, with sound, durable legs and feet? If not, be careful, even if the mare has remained sound. The problem could be compounded in the foal, especially if the stallion has a similar problem.

Finally, is the mare in good reproductive health? Here again, your veterinarian is your best ally. Have the vet give the mare a thorough examination, especially if she is older. There might be serious uterine scarring or the presence of cysts that could compromise her ability to carry a foal to term.

If you answered all of the questions in a positive way and still want to raise a foal, pick the best stallion you can afford and breed your mare. And good luck!

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Back in the days when horses pulled the plows and harvesting machines across agricultural America, it was not uncommon to see a team of horses trudging over a field with a young foal trailing behind one of the mares. Many farmers could not afford the luxury of allowing a broodmare to take a four- or six-month break from work just because she had given birth. She could have a week or 10 days off, then it was back into the harness with the foal tagging along when she was hitched to plow, wagon, or some other horse-drawn farm implement.

The mare also would be expected to continue working right up to parturition. I can remember my father telling stories of farmers unhitching a mare in the field and hustling her back to the barn because she was going into labor. He also told stories about stallion owners who would travel the countryside in a horse-drawn buggy, with the stallion tied behind. It wasn't unusual, he said, for a farmer to unhitch a mare which was in heat and have the stallion cover her on the spot. She then would return to work and the stallion would continue down the road.

I have no information on what effect these approaches had on conception rates and foal survivability. They were approaches necessitated by circumstances. It took a fair amount of hay and grain to keep a draft horse in good working condition, and that horse had to pay for its keep by toiling in the field to produce crops that enabled the farmer to support his family.

Tractors have replaced horses in agricultural America, and the equine today has become an animal used for pleasure riding and in a wide variety of competitive events. There still are some farmers who choose to till the soil with horses, but it is a matter of choice on their part rather than necessity. In parts of the West, saddle horses are used to gather cattle in the fall from mountainous terrain and broad, sweeping prairies. But, again, this often is a matter of choice rather than necessity. To the chagrin of ranchers who hold fast to the old ways, the advent of the four-wheel all-terrain vehicle has taken over many of the saddle horse's duties.

What all this means is that there are few occasions where an owner must put a broodmare back to work soon after delivering a foal. However, there also are a number of instances where it is advantageous to do so. Maybe the mare is a valuable show horse and to continue her quest for a title or award, she must return as soon as possible to competition.

Just how soon that will be after the mare gives birth will vary. A number of factors are involved, including the mare's temperament, whether she is to be re-bred, and, of course, circumstances involving the birth, such as whether it was a normal presentation or whether dystocia or reproductive injury was involved.

In some instances, foals are weaned early. In other instances, the foal is hauled to the show, but is kept in a stall while the mare performs. This can have detrimental effects if the foal should become agitated while in a strange environment and away from its dam. This is a time when temperament of mare and foal would figure into the decision.

Making decisions concerning when to put the broodmare back to work begins at the time of foaling. Was it a normal birth or were there problems involving dystocia and/or damage to the cervix or uterus? Did the mare accept the foal or did she fit into that unusual category of a mare which immediately rejected the newborn?

If the latter is the case, the decision-making process is easy. The owner is stuck with an orphan foal or finding a nurse mare. The mare, after being given a short break to recover from giving birth, will be ready to go back to work.

The post-foaling problems that can have an influence on how soon the mare is ready to return to work involve physical damage or trauma to her body. Fitting into this category are such serious problems as prolapse of the uterus, uterine rupture, invagination of the uterine horn, uterine hemorrhage, or a tear in the cervix. All of these are serious problems and must have reached a complete stage of recovery before the broodmare can be put back to work or bred again.

In the case of uterine rupture, for instance, one of the treatment protocols involves a laparotomy--surgical incision through the flank--and surgical repair of the ruptured area. One would want to make certain that complete healing of the affected areas had occurred before allowing strenuous exercise. The same would be true of a uterine prolapse that required surgical intervention.

When a cervical tear occurs, the prime concern involves getting it repaired so that the mare can continue to be a broodmare. In one study at Texas A&M, it was found that the pregnancy rate for mares with cervical tears that had been repaired surgically was 75%. It also was found that a number of mares in the study suffered a cervical tear in later pregnancies.

What all this means is that if the broodmare is to remain a broodmare and has complications during the birthing process, the number one goal normally is to solve the problem so that she can be become pregnant again. In most cases, putting the mare back to work is secondary at that point.

However, if there are no birthing-related problems, the decision-making process can take a different turn.

Alternative Birth

Of course, one way in which the broodmare can continue at work uninterrupted and have a foal is via embryo transfer. Other than a brief period when she is in the breeding shed to be teased, bred, and the embryo recovered, she can continue to be involved in whatever discipline has been chosen for her.

However, embryo transfer remains relatively costly for the average horse owner, and a recipient mare is required. It does provide a viable option for that stellar show horse. She can be kept in competition and, at the same time, pass on those valuable genes.

Work Schedules

Let's assume that you decided against embryo transfer. The mare has delivered a normal foal, and you want to get her back into a chosen activity as soon as possible. How soon can you do this?

There are no blanket answers. It will vary case by case, mare by mare, foal by foal.

In some instances, it is possible to do as the aforementioned farmers did and allow the foal to tag along. Here is a case where temperament would figure into the equation. If the mare is a trail horse, it might be possible to allow the foal to run along beside her, providing that the mare is a calm, relaxed individual. If she is not and becomes agitated every time the foal isn't at her side, it would make for an unpleasant outing.

There are other dangers involved with this approach. Foals which are several weeks of age and older become quite bold and are extremely curious. They might, for example, stray into a ditch where barbed wire lies hidden beneath the grass.

There also is the danger when riding in a group that some of the other trail horses might take a dim view of a youngster trotting up behind them and lash out with a back foot. The result can be serious injury to the foal.

If you choose to take the foal along for trail riding, one should exercise care concerning the company in which one is riding and be especially cautious concerning terrain. The best of all worlds in this approach is to be riding across smooth prairie, without fences and other obstacles, so that the youngster can run and frolic without danger of injury.

Some owners carry this approach a step further and take mare and foal to a horse show. This, too, can be a good news/bad news scenario. If the mare doesn't become excited when separated from the foal, she can be taken from the stall, shown, and returned. Of course, much also depends on the temperament of the foal. If it becomes highly agitated when left alone in the stall, there always is the danger of self-injury. Or, in some instances, it might be the foal which is shown.

It goes without saying that the mare's temperament will determine whether this is a worthwhile approach. If she is overly concerned about her foal, she is not going to provide rider or handler with a good performance. Same for the foal.

Some years ago when my wife and I were showing halter horses, I had an unpleasant experience with separating a mare and her foal at a horse show. The foal was about three months of age, and the show was in our home town, so we decided to show the foal in a weanling halter class.

I had separated mare and foal at home while teaching the youngster the rudiments of being presented at halter. It hadn't been a problem; the mare would whinny a few times, but that was about it. It was totally different at the horse show. Just being there seemed to agitate the mare.

When I led the foal from the stall, she began whinnying and charging about. To prevent damage, I tied her and led the youngster to the show ring. Instead of settling down, the mare became more and more agitated. I returned after the class and led the foal back to the stall. As I stepped inside, the mare had her rear end to me. Without warning she lashed out with both back feet. One of them whizzed past my right leg, but the other landed flush on the fleshy part of my left thigh.

The stiffness and soreness reminded me for some days afterward that not every mare and foal should be taken to a horse show. It continued to remind me that I had made a basic error when entering the stall. I should have made sure the mare was facing me before entering.

Early Weaning

One should be aware that the temperament manifested in home surroundings can change radically when in a strange environment. So, we return to the basic question. We have a healthy mare which has recovered from giving birth, and we want to get her back into action. How soon can we do this if we don't want to take the foal along when she competes or is ridden for pleasure?

One answer is early weaning. Again, a number of factors should be considered.

In bygone days, an orphan foal or one which had to be weaned at a very early age often succumbed or didn't develop properly. There are stories of orphan foals being raised successfully on cow's milk, but there are far more reports of those foals not developing properly.

Today, that has changed. Modern technology has presented us with equine milk substitutes that allow an orphaned or early-weaned foal to grow and develop as fast or faster than a foal which is nursing.

The traditional time to wean foals used to be six months of age. That is still a viable option, but if one wants to put the broodmare back to work as soon as possible, that time can be cut in half without serious side effects, providing the foal is placed on an appropriate diet.

Normally, says Dave Beckman, DVM, a practitioner in the Louisville, Ky., area, a mare's milk peaks in richness and nutrients at about 12 weeks and goes downhill from there as far as quality is concerned. This means, he says, that a foal can be weaned at three months of age without detrimental side effects, providing that it is eating hay and grain and that it is placed on an appropriate diet.

M. Phyllis Lose, VMD, author of the companion books, Blessed Are The Foals and Blessed Are The Broodmares, takes it a step further. She contends that it would be of benefit to the youngsters if all foals were weaned at 10 weeks of age, providing that they were placed on an appropriate milk substitute and a balanced hay and grain diet.

She contends that with today's milk substitutes, along with feeds that are produced precisely for foals, the hand-raised foal often surpasses those raised by mares as to size and development at equal ages.

To Breed, Or Not To Breed?

Still another matter to be considered when deciding how soon the broodmare can return to work involves breeding. If the mare is to be rebred, it can have a profound influence on the decision.

Again, there is no simple answer when this question is involved. This approach, too, must be made on a case-by-case basis. Is the mare one which readily shows heat, ovulates, and becomes pregnant without undue difficulty? Or, is she one who has "silent heat" and detecting her ovulation is tricky? How about hormone levels? Are they adequate or must they be supplemented?

How one answers those questions is significant. Let's assume that the mare is an easy breeder which shows heat and ovulates on schedule. If she is also a mare which doesn't become agitated when the foal is trotting along beside her on a trail ride or when traveling to a horse show with her, she could be returned to work a few weeks after foaling with no negative consequences for rebreeding.

However, if she requires reproductive therapy or fails to show heat, one would only complicate matters by allowing her to return to work, even though her temperament may permit it.

The first 60 days of a pregnancy can be difficult for a mare, Beckman says, because that is a time when her body is undergoing some fundamental changes in preparing to carry a foal to term. If she is being administered medications for any reason, he adds, it can further complicate the picture.

Earlier, we talked about early weaning of a foal and providing it with the proper nutrition. The same is true of a mare which is lactating, working, and carrying a developing fetus. This is a three-way drain on her nutritional resources. The mare which is working, nursing a foal, and carrying another will have high energy requirements that must be met to avoid possible long-term health complications.

It seems logical to conclude that broodmares can return to work quite soon after delivering a foal, providing that there are no birthing complications and that they are temperamentally capable. For those which don't meet the temperament criteria, there is the option of weaning the foal at 10 to 12 weeks of age.

Working Moms

We would be remiss, however, if we didn't look at the other end of the spectrum--how long can the mare be kept in strenuous activity before she foals again.

Beckman is of the opinion that the magic cutoff time should be at about seven months of gestation. The prime reason, he says, is that most growth occurs in the final trimester. At six months of pregnancy, the fetus is only about the size of a cat, he explains, but in the months that follow, it grows very rapidly.

Many foals, he says, weigh in at 125 pounds when born. When this is coupled with additional water weight, it might mean that the mare has gained about 250 pounds. In addition to the extra weight, he says, her center of gravity has shifted to the rear, producing more strain on abdominal muscles.

To ask a mare to perform under those circumstances, he says, would be much like asking a ballerina who has ballooned from 98 to 140 pounds to perform as effectively at the heavier weight.

Once the mare has given birth and she is healthy enough to return to work, special care must be taken to ease her back into a training regimen. As Beckman previously explained, extreme strain has been placed on the mare's abdominal muscles during the pregnancy and in the last days of gestation, and she likely received very little exercise during that time. That means light, easy works should be the order of the day in the early going of her retraining, taking into consideration her conditioning before pregnancy and parturition.

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Readers ask questions of equine reproduction experts

Earlier this year, The Horse made a request to its Horse Health E-Newsletter subscribers: What questions do you have for specialists about breeding your mares? Our e-mail boxes were flooded with replies. After narrowing questions down to several themes to be featured in this article, the questions were presented to two specialists in the field of equine therio-genology (the study of animal reproduction) and to one behavior specialist.

Michelle M. LeBlanc, DVM, Dipl. ACT, is a professor at the University of Florida College of Veterinary Medicine and a member of The Horse's Editorial Advisory Board. She was named the 2000 Theriogenologist of the Year by the American College of Theriogenologists (ACT).

Patrick McCue, DVM, PhD (Comparative Pathology), Dipl. ACT, is an assistant professor in the Department of Clinical Sciences at Colorado State University. His research interests include reproductive endocrinology and ovarian abnormalities.

Sue McDonnell, PhD, Certified Applied Animal Behaviorist, is the founding head of the Equine Behavior Program at the University of Pennsylvania's School of Veterinary Medicine, where her work includes clinical, research, and teaching activities focused on horse behavior. She is an editorial advisory board member for The Horse and author of the magazine's Behavior column (see page 79).

We thank readers for responding to our request. The remaining questions not addressed in this article will be considered for future article topics both in The Horse magazine and in The Horse Health Weekly E-Newsletter

How old is too old to breed a mare?

LeBlanc--The maximum acceptable age to breed a mare varies with her reproductive conformation and her well-being. What we do know is that when mares get older than 18 years of age, not every egg they ovulate is viable, similar to women when they get older. So we have to deal with poor egg quality, and some mares might have had many foals and have had wear and tear on their reproductive systems, which might make them more prone to urine pooling and uterine infections. When someone brings me a mare over 20 that is still having foals, I let them know they're very lucky.

I do a complete exam on older mares which have never been bred, because many times their cervix doesn't open properly during breeding. When they have semen put into them, either by natural cover or artificial insemination, they aren't able to clear inflammatory debris that occurs as a reaction to the semen. The mare's body reacts to the semen because it is perceived as foreign material, and her body has a white blood cell reaction to the debris. If the by-products of that inflammation reaction remain in contact with the uterine lining for more than 12 hours, they damage the uterine lining.

I pay particular attention to the cervix when I'm evaluating mares during estrus (heat). If the cervix doesn't open well, then we know we're going to have to treat the uterus accordingly after they are bred so that they can conceive. If they retain fluid and inflammation in their uterus, it is toxic to the embryo when it comes down to the uterus at 5 1/2 days, and the contamination will lead to the embryo's death.

Is it better to breed a mare that is "fatter" in terms of body condition scoring?

LeBlanc--There's not a lot of scientific data on overly fat or overly thin mares, but the work that came out of Texas years ago indicates that overly fat is not good for a breeding mare. So, if you're going by a body condition score scale of 1 to 9, you'd really like to have them between a 4 and a 7. Some of these mares with foals at their sides have their body condition scores brought down to a 3 or 3.5, but still conceive successfully. An overly fat condition is related to a lower pregnancy rate in horses. Typically, you want to breed a mare with a body score of about a 4.

If a mare you want to breed is thin and doesn't seem to be gaining weight, check her teeth and her de-worming history, and increase her feed. If she is in with a group of broodmares, make sure she's not at the bottom of the herd's pecking order. If so, get her out of the group and put her by herself or in a more amicable environment.

How long do you have to wait before breeding a mare after you discontinue use of Regumate?

McCue--This question is simple in that the time frame is fairly well understood. If a mare has been on Regumate for 10 days, two weeks, or any length of time longer than a few days, she should come into heat two to four days after coming off of Regumate. Most mares will be ready to breed within five to nine days after coming off of Regumate. In the mare, progesterone therapy doesn't narrow the window down as much as one would like it to, but it does give you the option of scheduling breedings. Also, the use of Ovuplant or human chorionic gonadotropin (hCG), both of which hasten ovulation, helps in this predictability process so that you can breed according to the availability of the stallion.

Can a mare that has had a rectal tear have another foal? What about a mare with a uterine tear?

McCue--Presumably, mares with severe rectal tears do not survive. The outcome is often fatal--if the mare has a full rectal tear, she will most likely be euthanized. Mares with mild rectal tears are given a block of time off from rectal examinations. They certainly can be bred, get pregnant, and foal 11 months later, but the difficulty lies in the examination period. If the mare has had a mild rectal tear, any exams during the next several days or the next week or two should be handled very cautiously. A lot of us depend on transrectal ultrasound examinations to determine preparedness for breeding or pregnancy. If the mare has had a rectal tear, sometimes we cannot do an ultrasound exam safely for several weeks. The mare potentially can be bred by natural cover or inseminated every other day while she's in heat, and the rectal exams avoided.

Virtually all uterine tears occur during spontaneous, unassisted foalings or dystocias (slow or difficult labors or deliveries). Tears can also be caused by blunt force of the fetus, or by an obstetrical manipulation.

Mares with severe uterine tears are at risk of facing severe peritonitis (inflammation of the smooth membrane that lines the abdominal cavity) and resulting death, or they might have to be euthanized. Additionally, peritonitis can lead into laminitis.

Small uterine tears might go unrecognized, or might result in only mild medical problems in the mare. After the tear heals, such mares can be bred, and in all likelihood, successfully carry a foal to term. Knowledge of mild uterine tears is very limited because we don't clinically recognize them. If a uterine tear is diagnosed and repaired successfully, the mare should recover nicely. It's kind of like the healing after a Cesarean section. If the damage is the result of blunt trauma incurred from the fetus or an obstetrical manipulation, the prognosis for the uterine wall is not as good as after the clean incision of an elective Cesarean section.

If a mare has had a known uterine tear (during foaling), she should not be bred back for a period of several weeks post-foaling--i.e., skip breeding on the foal heat and possibly on the subsequent heat.

Are there really mares which cycle "quietly?" If so, are these mares more likely to be aggressive or "mare-ish?"

McDonnell--First of all, there are mares that cycle normally and are completely normal, but they're very subtle about their estrus. I don't know of any research on this, but in my experience, those mares are usually not aggressive or "mare-ish" in other situations. They tend to be shy and not too demonstrative in all of their interactions with other horses and people.

We've taken a lot of mares like that (in the behavior program at New Bolton). If you tease them (to ascertain estrus) long enough and quiet enough, and every other day, you usually will get to know the mare's attitude and will notice a change. You can say, "For the last 10 days she didn't do any of that." Breeding mare managers of the farms will tell you that you should "know your mares," and know each mare's subtle signs (of estrus). Even though a breeding farm might miss mares with subtle heats, if you upgrade the type of teasing and change the method of teasing, you will see such a reaction. For example, have a mare loose in a paddock and a stallion in an adjacent stallion box so that the mare approaches him on her own terms. You'll see her approaching more. This type of mare might never show in a classic teasing situation.

In terms of the shy mare who cycles but does not show estrus behaviorally--we know the stallion can figure it out. These mares are the type that are sometimes scared of the stallion if you turn them out together after the mare has ovulated. Their fear and defensive behavior overrides estrous behavior. But, if you were to leave them together with plenty of space, the stallion would eventually get her bred.

With this type of situation, have the mare in a pasture with a safe fence line, and the stallion across an alleyway. The two horses will show you a change in behavior. It might not look as obvious as you would like, but they will show you a change. You might have to watch them for two or three estrus cycles before you're confident. Gradual introduction to the stallion is better for this type of mare rather than hobbling her, which would interfere with her expression of estrus.

There are some mares which don't show estrus, and act aggressive or
"mare-ish." I think it's very important to be very comprehensive in the evaluation of that mare's ovaries and hormones. As a behavior cluster, those mares usually end up having problems such as an early granulosa cell tumor that might be suppressing their normal behavior toward horses and people. Every time we get the mare who's not showing (estrus) and is aggressive, it turns out that there was something very unusual going on with her ovaries and hormones. As a veterinarian in that case, you would want to advise the owner or manager to get a mare reproduction specialist to do a thorough exam of her reproductive tract and hormones to rule out such things as an early granulosa cell tumor or some problem (physiological or hormonal) that's disturbing her ovarian function.

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