Have a Safe Delivery: Understanding Common Broodmare Problems

February 2008
If you’ve been breeding horses for any length of time, you know that things
don’t always go as planned. But often, handling the unexpected simply takes some education and preparation. Dr. Christianne Magee, DVM, MS, Dip ACT reviews here three of the most common problems encountered with broodmares,
their causes, and some solutions you can implement.

ImageDr. Magee earned her DVM at Tufts University School of Veterinary Medicine and her MS in Reproductive Physiology at Colorado State University. She was a Havemeyer Clinical Fellow in the Equine Neonatal Medicine and Intensive Care department at Tufts, did her residency at the CSU Equine Reproduction Laboratory, and is currently a Ph.D. student at the CSU Animal Reproduction and Biotechnology Laboratory. She is also a member of the Society for the Study of Reproduction, the Society for Theriogenology, and the American College of Theriogenologists.

Unpredictable Ovulation

According to Magee, one common question for many people is when to start trying to breed their mare. She explains, “A mare can look like she’s in heat and act like she’s in heat even when she hasn’t really started cycling normally yet for the year. She may be in transition for three to four weeks, acting like she’s in heat when she really isn’t, because she’s still trying to have that first ovulation. If you haven’t put her under lights and haven’t done anything to speed up when that first ovulation is, she probably won’t start to be regular until the end of March or the beginning of April (in New England).”

“To find out if she’s ovulating, you can have a vet ultrasound her and see if she’s already ovulated once for the season and you missed it,” says Magee. “Or, if everything looks good, you can give her something to induce ovulation. But if she’s not physiologically ready for it, that won’t work.

“You can also say, ‘It’s going to be snowing this time next year—not a great time to have a foal, so let’s wait another month when we know for sure it’s going to happen.’ If you try to breed before she’s ovulating, you’re not only wasting your money but you’re also increasing the risk of infection (if you’re hand breeding).”

Some people think that a mare will automatically ovulate on her first heat after foaling. Not necessarily, Magee says, “Just because she just had a foal doesn’t mean she’ll ovulate on the foal heat. It usually does, but there’s a 30% chance she ovulates normally, a 30% chance she doesn’t ovulate normally, and a 30% chance of something in between.

“The foal heat can be a very fertile time for the mare but only if you follow the rules and she follows the rules. If you didn’t breed her until April of last year and she’s not foaling out until March of this year, you probably had her in the barn under lights and have pushed things to your advantage, but there’s still no guarantee.”

Many breeders get caught in the notion that they must breed as early as possible. That’s really only needful for certain breeds, such as Thoroughbreds and Quarter Horses, who are all assigned a birth date of January first, regardless of the day the foal was actually born. In this case, a foal born early in the year will be more mature than its peers born later in the year.

“But if you don’t have a need to breed early, there’s no reason to rush it,” Magee says. “Mares are fertile at the right time of year so the foal hits the ground when the environment is best for it. And your mare will be fertile until August, so you have plenty of time.”

If you need to re-breed a mare as early as possible, Magee says, “You can speed up when a mare foals out—not a whole lot, but some. Say you’ve got a mare due to foal in February, you really need to breed her back in February, and you’re worried the mare won’t ovulate normally in her foal heat. Mares that are put under lights at the beginning of December as compared to mares not put under lights at the beginning of December can potentially foal out a little bit earlier.”

Broodmares aged three to eight are considered the most fertile, but there may be occasional individuals that fail to ovulate when expected. Those aged nine to fourteen will probably continue whatever pattern they had as young broodmares, but you may have issues breeding a horse this age for the first time.

Unpredictable ovulation is most common in mares over fifteen years of age. “And there may be some other surprises, especially if she has other health conditions like Cushing’s disease,” Magee says.

General good health is vital for all broodmares. She says, “Things like uterine infections, inflammation and health issues in other body systems can affect the cycle in any age mare. If she starts to change, it’s a clue to look into her complete health.”

Breeding on the Foal Heat

A number of breeders prefer to breed a mare on her foal heat, in her first cycle after birthing. But there are certain rules that must be followed in order to prevent problems from coming up.

Magee says, “Rule number one: your mare must have a normal foaling, which means no dystocia, no reaching in and digging around, no manipulating or pulling on the foal, no possibility of cervical tear. The foal was out in ten minutes and everything was perfect. Nothing went wrong during the foaling. Rule number two: the placenta came out normally, it came out within three hours, and it was intact. These two rules ensure that the uterine environment is in the best condition it can be, considering what just happened to it.

“The day ten rule makes sure the uterine environment is ready for an embryo. Post-foaling, the uterus needs roughly sixteen days before it’s nice enough for the embryo to survive. That means that if you’re going to breed her on her foal heat, she can’t ovulate before day ten. The reason for this is that after she ovulates, the egg is fertilized and lives in the fallopian tube for five or six days before it comes into the uterus. If she ovulates before day ten and you’ve bred her, the embryo will come into the uterus before it has had time to prepare. If you’re going to do something to induce ovulation, you want to make sure your timing is right so she ovulates on or after day ten.”

Magee says if you’re going to go through the hassle of trying to breed on the foal heat, you should have your vet check the mare between days five and seven. “By day seven, the mare shouldn’t have any fluid in her uterus, if she’s done a good job of cleaning herself up. Whatever fluid was in there should be kicking itself out. Your timing of this exam will depend on how important the breeding is. If I only have one straw of frozen semen, I’m going to check on day five.” Performing this exam can also allow you to call three days ahead to request shipped semen, which makes things go smoother for everyone.

“Nine times out of ten, all these rules will fall into place in a healthy mare,” says Magee. “But if she did have a little bit of fluid or something else happens to prevent you breeding on the foal heat, you only lose five or six days. You can always short cycle the mare by giving her something that has prostaglandin and make up those five days.” She adds, “But there is one caveat: if it’s February and she ovulated on her foal heat and you didn’t keep her under lights, she may not ovulate again until April.”

Placental Problems

Unlike the first two, problems with the placenta are potentially life-threatening situations that every breeder should be aware of. “There are two major issues involving the placenta,” Magee explains, “A ‘red bag’ and a retained placenta.”

In a red bag delivery, the placenta separates from the uterine wall without rupturing and the foal is delivered while still enclosed in the membrane. It can be caused by a number of things, such as infection, physical trauma like a kick, or prolonged hard labor, as when the foal is in the incorrect position.

“There are two components to the placenta,” Magee says. “The amnion is the grayish translucent layer that the foal floats in happily. The chorioallantois is the red, velvety layer that interlocks with the wall of the uterus, very much like Velcro. It is the connection and blood supply between the mare and the foal.

“A red bag occurs when the placenta is weakened and separates from the uterine wall early. That loosened part will begin to slip through because it’s detached and makes the mare think she’s ready to foal. What you see coming out of the mare is the bright red chorioallantois.

“This is a critical emergency. The placenta has separated from the uterine wall, so the foal is no longer getting oxygen from the mare’s blood, and the foal is trapped inside the placenta, unable to breathe air. You must literally grab the nearest knife, cut open the placenta (taking care not to cut the foal), and pull the foal.”

A retained placenta can follow an otherwise normal birthing. Magee says, “The cardinal rule is that the entire placenta must be passed within three hours of the foaling. Because a small piece of placenta can stay behind and cause problems, you and/or your vet must always examine the placenta to be sure it’s complete, particularly the tips of the horns. You can have a piece as small as a quarter left up there and it will start to release endotoxins. That alone can cause endotoxemia and laminitis and you can lose your mare.

“Gravity and the weight of the placenta will help it to detach and come out, but the non-pregnant horn is thinner and more fragile, so it’s more likely to stay attached and leave a piece behind. If you see placental tissue hanging out of your mare, you never, ever want to pull on it. Even a vet probably won’t pull it out unless he or she is very experienced.”

If you find the entire placenta has not passed within three hours, your vet will likely lavage the mare in an effort to help the tissue release from the uterine wall and also to remove the deadly endotoxins. Saving the mare can involve intense, round-the-clock care until the last bits of placenta have passed.

The potential for the loss of the mare due to a retained placenta is high, and the chances of an orphan foal surviving and developing normally aren’t fantastic. For this reason Magee says, “Checking the placenta for completeness is a critical element of good broodmare management.”

Broodmare Care

Successful breeding and management of mares takes attention to detail and a knowledge of what’s normal and what’s not. Keeping accurate records and staying in close contact with your vet can help you make each breeding count, and monitoring her closely throughout the pregnancy enables you to recognize problems early on. Your diligent and conscientious care will keep your broodmare and her babies healthy and happy.

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