Health check for young horses

In the first five years of life, young horses are prone to a particular set of physical problems. Here’s what you need to know about the 5 most common challenges.

In practically any discussion of horse health, older animals tend to get the bulk of the attention. And that’s understandable—once a horse reaches his teens his risk of developing a variety of problems increases significantly. And, of course, catching and treating them early is time well spent.

But the youngest horses in a herd face their own special health challenges. Some diseases and conditions found commonly in young horses—yearlings until about the age 5—are minor, but others can be as serious as any that befall older horses. Here is a quick look at five health issues you’re most likely to see in younger horses as well as what you can do about them.

1. Warts

Three young horses standing in a field
Health conditions commonly found in horses under 5 years old are typically minor, but still worth being on alert for.

Caused by a virus, these unsightly growths are a harmless rite of passage for most youngsters.

Small crusty growths caused by the papilloma virus, warts usually appear on a young horse’s muzzle but can be found on the eyelids as well. They are primarily a cosmetic concern and will go away once the horse’s body mounts an immune response against them.

“Typically we simply try to talk the owner into ignoring warts because, in most horses, they run their course quickly,” says Tia Nelson, DVM, a veterinarian from Helena, Montana. “Then they are gone and the horse usually has immunity against warts for the rest of its life.”

Occasionally, however, warts become so large that they obstruct a nostril or otherwise cause problems. “Once in a great while, we see some warts that are really awful—so thick and large that the young horse has a hard time eating,” says Nelson.

In those cases, she says treatment focuses on getting the horse’s immune system to recognize the virus as foreign and attack it. “We sedate the horse and use a pair of pliers to crush one or more of the warts deeply enough to make them bleed,” she explains. “This will often give the immune system a signal that an intruder is present, allowing the horse’s body to mount an immune response (to fight the warts) faster than when you simply leave the warts alone. Usually within a week to 10 days, the warts shrink up and are all gone. In the meantime, we may give the young horse some bute or Banamine to help with the discomfort while recovering.”


The earlier these growth-related bone and joint abnormalities are detected, the better.

A blanket term, DOD covers a wide variety of bone and limb abnormalities that can affect the soundness of horses in both the short and long term.

Some conditions, such as contracted0 tendons and crooked legs, are usually evident from birth, and your veterinarian will likely recommend immediate treatment. “With knock-knees and crooked fetlocks [at birth] intervention must take place within the first weeks of life, while you have a chance to make corrections as the foal grows,” says Bruce Connally, DVM, a veterinarian in Berthoud, Colorado, with a sports medicine practice.

However, some orthopedic condi-tions develop as a youngster grows, and others may not become apparent until he is in training. These include physitis (inflammation of growth plates at the ends of the long bones), osteochondritis dissecans (improper calcification of the bone directly under the cartilage layer) and bone cysts. Stated simply, all of these occur when the formation of cartilage at the end of long bones is over-stimulated or the conversion of cartilage to bone is somehow disrupted or inhibited.

Although there is a strong genetic component to many developmental conditions, they can also be caused by management—specifically, too rich of a diet and too much confinement. Although protein was once thought to be the nutritional culprit in DOD, recent research shows that carbohydrates—and sweet feed, in particular—may be the cause. Regardless of the nutritional underpinnings, the prevention is the same: feeding young, growing horses only the nutrients they need.

“Young horses should not be fed like steers in a feedlot,” says Nelson. “Horses should be fed to optimize athletic ability and soundness for a long life of useful performance. We want these babies to grow well, but too much of a good thing is not a good thing. I always prefer babies to be on the slim side rather than obese. It’s better for their joints and their whole body and longevity. You don’t want them starving, but I like to see them athletic rather than fat or growing too fast,” she says.

Lack of exercise can also lead to DOD. “It’s amazing how many people make the mistake of putting the baby in a stall so he will be protected or to get him ready for halter classes at a show,” says Connally. “Too much pampering and protection will result in a horse that won’t hold up as an athlete.” That said, too much forced exercise can also be detrimental. Turnout in an active herd will encourage most young horses to move enough to keep their joints healthy without damaging them.

However a youngster is managed, be on the lookout for DOD as he grows. “By the time a horse is a yearling or 2 years old, trying to correct these with management is nearly impossible,” says Connally. “By then we’ve lost a lot of our opportunity to affect the growth plates; they are already closed or closing.”

Connally adds, however, that treatment is still possible: “If you x-ray those joints you can see the lesions and figure it out and get some treatment. In many instances it will be surgical treatment, although people have done some other things like shock wave therapy, which might help.”


Deworming is vital because certain parasites can overwhelm a young horse’s still-developing immune system.

Because the immune system is still maturing during the first years of life, young horses are particularly susceptible to certain internal parasites, such as ascarids0. The solution, of course, is deworming. However, unlike older horses, who do best with targeted deworming primarily based on fecal egg counts, young horses—particularly foals and weanlings—benefit from deworming based on a schedule devised to protect them from the most common threats: ascarids and small0 strongyles, which can be acquired through a dam’s milk.

By the time a youngster is a year old, he may have developed sufficient immunity to be dewormed based on fecal egg counts like mature horses, but your veterinarian will determine the best approach. Immunity will continue to build until the horse is around 5 years old, so his treatment plan may be continually adjusted until then.

Keep in mind that parasite control, in young and old horses alike, also involves management measures, such a picking up manure from pastures and rotational grazing. “The parasite life cycle requires that the worm eggs hatch and then the larvae move onto the grass,” says Nelson. “Then it goes through stages until it gets to the infectious stage, to be eaten by a horse. This is where management becomes important. If you get horses off the pasture before the infectious stage is present, the horses won’t become re-infected with worms. Rotating pastures can be very helpful.” This is particularly true in hot, dry areas, where environmental conditions will kill the larvae quickly.


 Deworming is vital because certain parasites can overwhelm a young horse’s still-developing immune system.

Like internal parasites, infectious diseases such as strangles0, influenza and rhinopneumonitis0 are more likely to strike young horses because their immune responses are not fully developed. The risk is heightened when the youngsters begin to leave the confines of their home farms and come in contact with a host of pathogens they haven’t encountered before. This, combined with the stress of transport and changes of environment, can lead to seemingly perpetually runny noses.

Vaccines, of course, are a vital defense against the worst illnesses. But the best vaccination schedule for a foal, weanling or yearling will depend in part on his geographic location and lifestyle. Your veterinarian can help you determine the right plan for your horse.

“It makes sense, vaccination-wise, to try to protect young horses during their weanling through 2-year-old years as they move out of the biosecurity of their home pasture,” Connally says. “ You need to start on their first vaccinations at the recommended ages and do the appropriate boosters.”

The American Association of Equine Practitioners (AAEP) maintains age-related vaccination guidelines for both core and risk-based vaccines. “The main recommendations regarding influenza, for instance, is to vaccinate horses 3 years old and under or any horses that are competing and subjected to exposure from horses outside their own farm,” says Connally. “Flu is one of the big ones we think about for youngsters, along with tetanus0. You want to get the immunity started.”

Vaccination alone, however, isn’t enough to protect young horses from infectious diseases. “To rely on vaccines without biosecurity is a huge mistake,” says Connally. “To prevent strangles, influenza and rhino requires a good biosecurity program.”

Biosecurity measures focus on reducing a horse’s exposure to pathogens—from other horses to water buckets—especially when traveling. “When I worked with racehorses I had one client who every year could count on his 2-year-olds doing fine in training and staying incredibly healthy at his place—and then he’d take them to the track and half of them would be unable to run in their first race because of respiratory disease. This illustrates the biosecurity issue,” says Connally. “Exposure is a big part of the picture.”

When you take a young horse on the road, don’t allow him to come in direct contact with any unfamiliar horses. This means no nose-to-nose “introductions,” no matter how cute. Also, do not share tack, water buckets or other equipment with unfamiliar horses. Back at home, isolate any potentially ill animal, those returning from stays off the farm or those with unknown vaccination histories until you are sure they are healthy.


Regular dental examinations from an early age can help identify many oral problems when they are still treatable.

Like older horses, youngsters need regular dental care—or at least examinations. Foals who have bite abnormalities, such as parrot0 mouth, can outgrow them, but only with regular dental care. “A person has to be proactive while these babies are young and the jaw is still growing—and you have a chance to make a difference. There is a lot of plasticity in young growing bones,” says Nelson.

But even if a horse has a normal bite at birth, it still pays to monitor his teeth and mouth as he grows. Temporary molars usually push up through the gums sometime during the foal’s first month of life, and these “baby” teeth remain in place until they are pushed out by emerging permanent teeth. In humans, baby teeth come loose and fall out as permanent teeth come in, but in horses the baby teeth deteriorate as the new permanent teeth start to erupt. They become hollow and are then called “caps,” which are shed as the permanent teeth come in. The first set of caps shed when the horse is about 2 ½ years old, the second set at 3 years of age, and the final set of caps comes off when a horse is about 3 ½ to 4 years old.

Not all young horses follow a textbook schedule, however, and complications may develop. Sometimes these caps do not detach from the gums as they should when the permanent teeth are pushing them out, explains Nelson. This condition is called a retained cap and can cause pain, inflammation of the gums and, if it involves the upper jaw, sometimes sinus problems. If the retained cap is not removed, it may force the new tooth to grow in at an improper angle. Emerging permanent molars may also become impacted if the jaw is too narrow. It’s common to see these as “tooth bumps” under the lower jaw in a 3- to 4-year-old horse. Most go away over time, but some need veterinary attention.

Young horses are, for the most part, a pretty healthy lot. Chances are, with attentive care, your youngster can move through adolescence with minimal, if any, physical problems. However, it’s important to remember that young horses are prone to certain conditions and to watch for even the subtlest signs of trouble. “Anytime a young horse is not being agreeable when starting training, we check teeth, we check feet and we check backs,” says Nelson. “Attitude is pretty rare, in my opinion, in young horses. There’s usually a physical component involved.” 

This article first appeared in EQUUS issue #465,

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