December 1999

Tips for the Mare Owner

by HEATHER SMITH THOMAS

Getting mares bred and keeping them foaling every year can be a challenge. There are a number of things a breeder can do, however, to improve the chances of success. Dr. John Migliore, (Lone Oak Veterinary Clinic, Visilia, Calif.), is the veterinarian for Oswood Stallion Station at Porterville. He has several suggestions for mare owners, looking at it from the perspective of a veterinarian dealing with mares coming to a stallion station to be bred, and also working with shipped semen.

As he points out, many stallion stations today (depending on the breed and on the individual horses) often ship a lot of cooled semen as well as breeding mares at their facility. "So we have two things to look at. First, the mare: when she arrives, we need to know how well she has been prepared to be bred.

"As for a mare coming to the stallion station, ideally you want mares that are in good condition, with no uterine infections or any other problems. Depending on the particular facility, usually we do some preliminary work to make sure we have every opportunity to get the mare pregnant on her first heat cycle. That’s our objective. So we usually require a uterine culture, or we will do one ourselves, along with a cytology of the mare, to make sure there are no problems as far as infection is concerned."

He always does an ultrasound evaluation of the mare’s reproductive tract, "to look for any systic structures in the uterus that might fool us as far as thinking the mare might be pregnant. Sometimes uterine cysts will mimic early pregnancies, and so we try to make notes of the locations and sizes of cysts–so we aren’t fooled at an early pregnancy detection, calling her in foal when in fact she is not." He also evaluates the ovaries, to make sure there are no abnormal structures there as well.

"That’s the basic beginning of how we deal with these mares, then it’s a matter of getting them into heat–whether we use a prostaglandin or have them come into heat naturally," he says. "I think teasing is very important, along with making notes on the individual mares, or at least having the same person teasing the mares so you can recognize any minor behavioral changes which may be very significant. Some mares are shy and they don’t show very well, while others will show heat half a mile away."

He says it is important to try to minimize the number of times a mare is bred, and to also put the optimum number of sperm into her at the time of breeding. "We try to have only one or two services per cycle, so we don’t breed these mares excessively–because that can be detrimental sometimes as well."

BRINGING MARES INTO HEAT AT THE RIGHT TIME: "We do manipulate their cycles to some degree with drugs, getting them to ovulate on our schedule, for instance at times when we have a lot of mares for a particular stallion. We use HCG or the new product, Ovuplant. Last year was the first year it was available in the U.S. Fort Dodge is the distributor in this country. It’s an implant that’s put under the skin."

He feels that Ovuplant is a useful product. "When using HCG you generally have to have a certain size follicle before using it. The consensus is that 35 millimeters is the smallest size follicle you should use HCG on, whereas with Ovuplant, a lot of people feel you can implant mares when follicles are around 30 millimeters in size. You thus have a little more time to manipulate their cycles with Ovuplant."

Migliore says that once you administer the drug, whether HCG or Ovuplant, the mare will ovulate. "With HCG you can expect her to ovulate around 30 hours after you gave it, plus or minus six hours. With Ovuplant, there’s been a very wide range of comments. In talking with veterinarians from Canada, who have used the product more than we have, they’ve said mares will ovulate as little as 24 hours or as much as 48 hours after you implant them. A lot of people feel that 36 to 40 hours are very realistic figures for onset of ovulation after the implant. So in some respects, the jury is still out on this," he says.

USING ULTRASOUND: "I think another thing we are doing now that hasn’t been done as much in the past is following mares after they have been inseminated or bred, checking them with ultrasound to confirm an ovulation–to be sure you don’t need to breed them again. In our case, we probably check mares 98 percent of the time. Sometimes it’s just not practical or feasible to ultrasound them, and then we just do a rectal palpation, but ideally we like to use ultrasound because you can find some very useful information. When you think these mares have gone out of heat or have ovulated, you can confirm ovulation."

He says another thing being recognized and talked about in the last couple of years is that "mares can have an anovulatory follicle, where the follicle gets nice and big but it doesn’t ovulate. It basically just degenerates. We see a number of mares that will do that. Those particular cycles are not fertile. So we usually contact the mare owners and make them aware of that fact.

"We also use ultrasound after a mare has ovulated, to examine the uterus for fluid accumulation. We’ve recognized in the last couple of years that some mares’ cervixes will not relax adequately, or the mares have an inflammatory reaction to semen or the extender that put in the semen, and they will have a large volume of fluid after they’ve ovulated. This makes a poor environment for a pregnancy. Usually on these mares, we will administer oxytocin post ovulation to hopefully cause the uterus to do some contracting to expel the fluid. A lot of times we’ll do uterine lavage on these mares using lactated ringers to flush out the fluid, so it might make a better environment for the embryo when it enters the uterus on day five." He also points out that you’ve got to give the oxytocin or do the flushing within two to three days after ovulation, while the embryo is still in the oviduct.

PROBLEM MARES: Sometimes you run into things you don’t anticipate, or have to deal with problems that a certain mare encounters all too consistently. Some mares will have an occasional problem, but others, "unfortunately are fairly consistent with certain types of problems. Some have problems with fluid accumulation and we can almost predict they will do it. Others may have a really good cycle, but will not conceive, for whatever reason and then next time have a terrible cycle and then the next time she’ll have a perfect cycle and conceive. With some mares it’s variable, while others, unfortunately, are pretty consistent with their problems and it’s quite discouraging."

He says these are the times it’s important to communicate with the mare owners and let them have a veterinarian of their own choice discuss it with them. "This allows everyone to understand exactly what is going on."

Whether the mare is at a stallion station or an individual farm or at a veterinary facility to be bred, Migliore feels that "the first important thing is she be properly screened to make sure she is, in fact, ready to be bred. Unfortunately, sometimes we get mares that are infected or have a tremendous amount of uterine cysts or some other problem, and we know right off the bat that we have a difficult situation. So we call the owners and talk to them, so the owners can be made aware of the problem if they haven’t already been made aware of it. This way they will understand the situation before they have too much board paid on the mare and they can’t understand why the mare is not in foal."

HELPFUL TIPS: Another tip for breeders that Migliore recommends is that "early in the year it also helps to put mares under lights to make them cycle quicker. It takes a minimum of 60 days under lights before mares begin cycling normally. Even mares that are in foal, if they foal early in the year, they can benefit from being under lights also. It’s not a panacea, however. We have mares that have been under lights and have some other problem–because some of them just don’t cycle like they are supposed to, even when they’ve been under lights the proper amount of time. We generally recommend 16 hours a day. It’s actually detrimental to have them under lights 24 hours a day; you don’t want them under lights all the time. You try to mimic nature’s ideal breeding season. This is one way you can get a jump on Mother Nature."

Once the mares start cycling, he says that "when they are in good estrus you can go ahead and do your cultures and cytologies, and make sure you are not dealing with any infections. If mares have had problems in the past, sometimes we recommend doing an endometrial biopsy, or a uterine biopsy, and look at them histologically, to see if in fact we do have some changes in the endometrium that would indicate that they will be difficult to get pregnant or to maintain a pregnancy."

What he looks for on a biopsy is fibrosis (scarring), or low-grade or chronic infection, which can also lead to fibrosis. "We also look for the degree of glandular tissue, which is important to maintain pregnancy. We grade them on a score of one to four, to depict the percent of chance for conception and bringing a pregnancy to term. Grade 1 is normal. Grade 2 mares have a 50-50 chance of conceiving and carrying the foal to term. Grade 3 mares have only a 25 percent chance or less that they will conceive and carry the foal."

He says that sometimes they’ll see mares that have been diagnosed in foal but are no longer pregnant. "The mare may have had an early embryonic death or may have aborted at three to five months. A lot of times we’ll do a biopsy on these mares to give a possible explanation as to why they did that."

HORMONE THERAPY: Another possible reason for pregnancy loss is low progesterone. "Some farms will put mares on Regumate for varying degrees of time, if they feel there’s a hormone problem, and we’ll do it sometimes, too. Usually we’ll submit some samples for progesterone assays to see if mares are low. If they are, then we do recommend to the owners that they maintain they mare on Regumate. Our recommendations are usually to give it for about five months (150 days). Other veterinarians might recommend 300 days. There’s a tremendous variation there; everyone has their own opinions on it, but hormone supplementation can definitely be helpful."

He says "another treatment that has come into vogue in the last few years is testing mares for thyroid function. Some people feel thyroxin is very important, as well. Some breeders want their mares on thyroid supplementation. So that’s another hormonal therapy that some people test for and recommend."

Dr. Migliore says these various suggestions give an overview of breeding mares, looking at it "from a veterinarian’s perspective, to get people thinking about some of the reproductive aspects they may need to be thinking about for breeding season."