Premature Horse Birth: Preemie Foals
Premature Horse Birth: Preemie Foals
When a horse has a premature foal, veterinary care for that animal has many similarities to neonatal care for premature humans.
There are also quite a few differences. However, the ultimate goal is similar: Get the baby’s body ready to function on its own outside of its mother’s body, while encouraging the intake of nutrients and fluids.
It’s quite the journey, but horses often surprise us with their resilience and determination to thrive.
What is a Premature Foal?
There’s a much wider range of time for gestation in horses than for people.
Gestation length can vary from around 330 to 360 days, according to Dr. Michelle Linton, a veterinarian at the New Bolton Center at the University of Pennsylvania School for Veterinary Medicine.
“Anything less than 320 days gestation is considered premature,” Dr. Linton adds. “But that is relative to what a mare’s normal due date is, if she has had foals before.”
Dr. Laura Dunbar from Ohio State University’s Department of Veterinary Clinical Sciences says that even if a foal was born after a “normal” gestation, the foal might not be fully developed if the expected gestation length was supposed to be longer.
If a foal is born prematurely, it will definitely need an immediate veterinary examination and perhaps a stint in a veterinary hospital to manage the nursing needed to bring the horse to health.
Dr. Dunbar says premature foals can experience several problems.
“The most common characteristics of prematurity in neonatal foals include low birth weight, weakness, a silky hair coat, floppy ears, limb laxity and incomplete bone development,” she explains. “They can have inadequately developed energy and fat stores, which can cause problems with regulating body temperature and blood sugar.”
The main concerns Dr. Linton immediately looks for in a premature foal are lungs and kidney function.
“Horses develop the chemicals needed in their lungs to help them exchange gases very late in gestation,” Dr, Linton says.
Veterinarians are also concerned with the foal’s heart function.
“Is their heart pumping the right amount of blood?” Dr. Linton asks. “Do their blood vessels have the right amount of pressure? Does the heart have the right amount of tone to get the blood where it needs to go? There are a lot of crucial changes that occur when they’re born, and sometimes if they’re too early, those changes don’t occur.”
An immediate concern, but one with long-term consequences, is bone development. Dr. Linton says like humans, equine bones begin as cartilage, before gradually turning into bone. One of the last parts to form in the womb is called the cuboidal bones – the small, square bones in the horse’s carpi and hocks.
“The cuboidal cones are the last ones to turn to bone,” Dr. Linton says. “If they are born without those being completely ossified, they’re still cartilage. Cartilage can be strong, but it’s squishy, and if they get up and run around on that cartilage, they can actually crush it, and then bone will form, but it will form in an abnormal shape.”
Part of the treatment of a preemie foal depends on why the horse was premature.
“Some are premature because the mare was sick – she had an infection and the foal has been exposed to an infection as a fetus,” Dr. Linton says. “Those horses may require a lot of treatment. Or you can have a premature foal born because the mare went through a period of stress. In that case, it could be reasonably healthy, just small, with underdeveloped bones.”
Regardless of how sick the foal is, all premature foals require a team dedicated to their care, says Dr. Linton, mainly because they have to be kept off their feet.
“A human baby is not going to walk for a long time anyway, so they’re going to be where we can monitor them,” Dr. Linton says. “Foals – their first instinct is to get up. So having around-the-clock monitoring for them is a big part of it.”
A lot of the nursing care is checking for infection and administering antibiotics if needed, checking lung function and applying intranasal oxygen if needed; as well as checking on kidney function and levels of hydration by monitoring the urine and feces output and addressing needs with intravenous fluid and nutrition.
If the foal is having problems with its cardiovascular system, it can be given medications to help support function, and keep the blood pressure appropriate.
“Care can be broken into medication, and then supportive and nursing care,” Dr. Linton says. “Once they’re started on a medication, then we make adjustments, routinely, because you’re always assessing them.”
A big part of the care if nursing – can the foal drink milk? Is it too small to reach the udder? Does the veterinarian want the foal to stand up and drink?
“If the foal’s bones aren’t fully developed, we may not want them to be up and around,” Dr. Linton says. “So we almost train them in a way to stay down more than they would if they were a normal foal.”
Preemies stay in a confined area, next to the mare so they can interact, but in a smaller stall so the foal can get up and walk around, but not create much impact on the legs.
Nutritionally, foals are like human babies and must be fed every couple of hours.
“We milk the mare every two hours and feed the foal every two hours,” Dr, Linton says. “A lot of the nursing care surrounds feeding the foal.”
If premature foals can’t tolerate milk because their intestines aren’t functioning adequately, the foals might get nutrition by intravenous feeding, which requires constant monitoring.
If the foals are too weak to stand or their bones aren’t developed enough, they have to be repositioned every two hours to avoid lung problems, Dr. Linton says.
“The way the lungs are, if they get down on one side of the lungs, it doesn’t inflate well with air, and they’re very prone to getting pneumonia,” Dr. Linton says.
A foal spending a lot of time on the ground, and trying to get up can scrape its legs easily, so veterinarians will need to care for those wounds. A foal might also scrape its eyes on the ground, so veterinarians look for these kinds of injuries.
“It’s very similar to a human neonatal ward,” Dr. Linton says. “They are animals, and they’re bigger and stronger, but I’ve had volunteers come out that actually work at human NICUs at children’s hospitals, and they are surprised at how similar it is.”
When a foal is over the immediate hump of making sure the lungs, heart and other organs are working, it comes down to the bones, Dr. Linton says. Sometimes it can take five months for a foal’s bones to properly develop enough to run around. And during that time, it is vital for the foal to be confined to avoid crushing the cartilage through the impact of running.
“Some facilities aren’t set up to confine a foal that much,” Dr. Linton says. “And as their bones form, you want to make sure that the angle of the leg is growing correctly.”
Sometimes, Dr. Linton’s team will hold a foal for a week or two and other will stay five or six months – not solely in intensive care, but with close monitoring, nursing and general care.
Before discharge, Dr. Dunbar looks for a foal to be able to stand and nurse on its own, without additional intravenous fluid or nutrition supplementation, and she wants to be sure secondary infections have been treated.
Will the foal grow up to be normal? Will they have any setbacks? These are the biggest question from the owners of premature foals.
“Premature foals that survive the neonatal period often grow to normal size and function as adults, although there is some information that they may have fewer placings and earnings as athletic horses,” Dr. Dunbar says. “Some severely premature foals may remain small, and abnormalities such as incomplete ossification may predispose them to deformities within the developing bones or early osteoarthritis.”
Dr. Linton says discharge depends on the degree of prematurity, severity of abnormalities and “unreadiness” for birth.
“Often, what we see with premature foals, is that by the time they are technically supposed to be due, they are closer to looking like a normal foal, but if they have been really sick, they might be a little bit behind in their growth especially if they were confined. They’re not getting out and running around, growing muscle.”
Dr. Linton says usually by the time the preemie is a yearling, it might be a little behind other yearlings, but by the time it is 18 months to 2 years old, it has caught up. And in her experience, by the time the horse if 2 or 3, observers wouldn’t know the horse was premature.
“I’ve had some that, by the time they were 6 months old, you wouldn’t know they were premature – but that depends on how sick they were and how premature they were to start with,” Dr. Linton says.
The good news is, in Dr. Linton’s experience, 85 to 95 percent of sick foals she works with end up going home as healthy foals.
“There might be an emotional roller coaster to go through because they change so quickly, but there’s a good chance that foal will be fine,” Dr. Linton says.
Dr. Linton says the mare herself is going to be the best indicator of what’s going on in her pregnancy, but it can be hard to tell if it’s her first pregnancy.
“My best advice is to watch her udder – watch for mammary gland development, which usually indicates that she’s getting close to foaling,” Dr. Linton says. “If the mare goes from one day not having any development and the next day she has developed a significant udder or even wax (on the teats) at 300 days gestation, that usually means she’s thinking about foaling. She will need to be evaluated by your veterinarian immediately.”
Listen to your mare and watch her closely – check her udder twice a day as she gets closer to her due date. If she’s losing weight, or has a fever, call your veterinarian. A high fever adds a lot of stress to the pregnancy. And if she’s losing weight late pregnancy, that could be because she’s putting everything into growing the baby and her nutritional plane needs to be increased, or it could be a sign that something is not right.
And make sure your mare is healthy, vaccinated properly and not exposed to horse going on and off the property to avoid her contracting an illness that could affect the pregnancy.
Despite excellent care, there’s still a chance your mare could foal prematurely. That’s why Dr. Linton suggests working with your primary veterinarian to set up a plan. When can the veterinarian come out, should an emergency arise? If you are several hours away from your usual veterinarian have a contingency plan for another veterinarian who is closer to you.
“Always have your trailer ready,” Dr. Linton says. “I would have the trailer set up and hooked up at night so you don’t have to dig it out and find dividers and move things out of there in an emergency. It needs to be ready to go.”
If you have other mares on the property, have someone available to watch them should you need to transport a more and foal to the veterinarian.
“It’s a real team approach between you and your veterinarian,” Dr. Linton says. “Talk to your veterinarian and walk through potential problems, before they arise.”
Dr. Michelle Linton, BSc, BVMS, DACVIM, is a staff veterinarian for internal medicine at the University of Pennsylvania School of Veterinary Medicine’s New Bolton Center. Her degrees in veterinary medicine are from Murdoch University in Western Australia. Her clinical specialties are large-animal internal medicine and neonatology/perinatology. Her research is focused on fetal monitoring, perinatology, abdominal ultrasounds of foals and colic in foals.
Dr. Laura Dunbar is an assistant professor in equine internal medicine at Ohio State University’s Department of Veterinary Clinical Sciences in Columbus, Ohio. She has a bachelor's from Clemson University, interned at Rhinebeck Equine and attained a veterinary degree from Cornell University. Her clinical interests include equine neonatology, equine critical care and gastrointestinal disease.