Reasons for Chronic Weight Loss in Horses

Last Updated on October 29, 2020 by Allison Price

horse in grass

Weight loss is due to the fact that the body uses more calories than it absorbs. There are many possible causes of persistent weight loss in the horses. Like poor quality and/or insufficient supply of feed, health and disease issues. And social contact and horse competition.

Chronic weight loss may also be the consequence of malnutrition. Caused by deliberate negligence, ignorance, owner’s economic hardship, sickness. Also, poor dentition, parasites, pecking order or seasonal change in pasture availability. Persistent weight loss will outlive horses. Horses are able to lose 30% or more of the body weight and still be able to survive. Horses will have a little muscle mass in this state and will be very sluggish.

To return to a stable body state, they will need careful care and a sound diet program. Even when equipped with the best treatment… horses that lost 50 percent or more of the body weight will not survive.

To know more about this and prevent your horse from losing weight, keep reading!

Causes of Losing Weight

Consistent Bad or Limited Feed

Low quality or minimal food is usually the most common cause of weight loss. In persistent weight loss, forage (hay / pasture) has a significant role as it is the main component of the diet. Moreover, the consistency of hay and pasture is difficult to assess the right way. In other words, an individual can provide their horse with adequate forage. But the forage is of such poor quality that it cannot be properly digested by the horse.

If your horse has free-choice access to as much forage as they eat and still lose weight… he needs to have better quality of forage. Furthermore, it is possible to add a grain concentrate. To provide extra nutrients that are lacking in low quality forage. Other common mistake when feeding horses is not providing enough feed.

two brown horses

Problems of Health & Disease

Topics ranging from dental problems to parasite infestation to diseases… are part of health and disease problems.

A major cause of weight loss in horses is dental problems. If horses are unable to chew their feed properly, the nutrients in the feed will not be utilized. 

Signs that dental problems occur in a horse are: 

  • Falling feed while chewing
  • Foul smelling breath 
  • Nasal discharge
  • Swelling of the face

As other disease processes can be present in the horse’s mouth… it is necessary to do a full oral exam and not only look at the teeth.

Internal parasites, like worms, compete for nutrients with the body of the horse. And oftentimes contribute to weight loss. Parasites can become resistant to several common de-wormers. So, to rule out this issue, it is vital for your vet to check the feces for parasite eggs. Even then, larval parasites that are not present in routine fecal examination… may also be included. And treatment for the larval parasites may be a need to avoid persistent weight loss.

Weight loss can result in a variety of other illnesses and chronic health issues. Any illness that affects a horse can raise requirements for both protein and energy. And often results in weight loss. Treat the disease or health condition first. And overcome in order for horses to recover from the illness and gain weight.

Social Interaction

Horses can be very violent towards one another, as most horse owners have observed. The complexity of the inherent hierarchy of superiority is higher. Especially when you are group feeding horses. Not only can smaller, younger and more timid horses are being forced away from the feeders. But high levels of stress can be encountered, including not only spending more energy. But also predisposing them to health issues such as stomach ulcers and colic.

It is important, in general, that underweight horses are being fed in a separate way. This will guarantee that they are getting the amount of feed that is for them.

Other Causes of Weight Loss

Here are several explanations and what to do if you have a horse that is either not putting on, or keeping a good weight. There are many explanations why a horse… despite eating what appears to be a healthy diet, can lose weight or fail to put on weight.

The most evident explanation that a horse will lose weight is because it doesn’t eat enough. Horses have varying dietary requirements during their lives. A young horse should be in balance always. But not overweight at all, because this creates its own problems. Young horses must be on the lean side. You must be able to feel the ribs. But they must not be prominently sticking out. Joint issues can be because of overfeeding at this age.

Working Horses

A simple hay and grass diet may not be enough as a horse enters its working life. Horses that are being used for casual rides would be fine. But grain or other concentrate will need to be applied to a horse that works hard. Like a show horse, a draft horse, long-distance trail horses. Or other high-performance horses.

person riding brown horse

The energy and nutrients it need cannot be provided by hay or grass. You may find your horse losing weight if you are using your horse for competition. Or riding challenging trails. And pulling logs out of the bush day by day. And it will take a few extra meals so that your horse is always in good shape. For broodmares, it’s not unusual to lose weight while they feed a foal.

Traveler with horses and donkey crossing river in highland

Weight Loss During Summer

It isn’t uncommon for horses to lose weight in the months of summer. A horse will run down very easily with the heat with pesky biting insects. Senior horses and those with very sensitive skin… are very vulnerable to the stress caused by heat and bugs. Most thoroughbreds have this issue.

Also, aside from shielding horses from the heat and the bites of mosquitoes and other flies… horses who have difficulty holding weight on in summer will enjoy extra feed. Whether it is good-quality hay in the barn where your horse can relax and eat without worrying of the bugs. Or a supplement to help gain the weight.

Cold Weather

Cold weather suggests that your horse needs more energy to keep him warm. It will help your horse remain in shape by providing a warm blanket and a snug shelter from the wind and wet. Offering plenty of high-quality hay is the perfect way to keep your horse warm and at a healthy weight.

Older horses also have difficulty holding themselves in good shape. They may not digest food efficiently when they age. Also, they will have a tougher time keeping themselves warm. And pains caused by arthritis and other chronic pain may cause stress that leads to weight loss.

Dental Problems

Dental issues are the most common cause for older horses to lose weight. The horse ‘s teeth will not grow forever. And they will inevitably fall out. They can have sharp edges and hooks. And these make it difficult as well as painful for the horse in chewing its food efficiently. Even though they have not fallen out.

Horse, Horses, Horseback Riding, Animals, Animal

This unique concern is not limited to older horses. A lot of horses may have dental issues in the prime of their lives that interfere with chewing. For your horse during its lifetime, daily dental care is necessary.


At any stage of life, parasites will take their toll on horses. That is why de-worming always is necessary to prevent a heavy parasite load. It does not only cause the weight to lose. But it also damages internal organs. Also, external parasites may also be a problem. A virulent lice infestation may cause your horse to lose its condition. Foals as well as older horses can be particularly affected.

Pecking Order

There are bullies and underdogs in a herd of horses. Including a small herd like the one we have in our own farm. The underdogs are also bullied away and the best pasture. This may lead to weight loss. Because besides to getting overwhelmed… the horse that is being bullied does not get enough to eat.

Disease & Illness

Weight loss can be because of a variety of health issues. Ulcers are prevalent. Especially among performance horses. Appetite and digestive issues contributing to weight loss may be caused by: 

  • EPM
  • Gastric Ulcers
  • Cushings
  • HYPP
  • Mineral and/or vitamin deficiencies
  • Conditions such as cancer or kidney and liver disorders

Hay Quality

Hay is the greatest component of a horse ‘s diet. As described above. If a horse eats all its grain and hay, but still loses weight, the quality of the hay may play a role in losing weight. Although the quality of pasture forage is difficult to measure. You can still check the quality of the hay forage you give your horse.

horse eating grass

Even if you regularly buy the same type of hay from the same supplier. According to the maturity of the grass when harvested. As well as the environmental conditions of the grass’ location… the hay quality will vary from time to time. You can add a grain concentrate to your horse’s diet to make up for the nutrients that are lacking from the hay. If better quality of hay is not available.

Weight Loss Monitoring

A proper estimation of the body weight of the horse and the score of the body condition are a need. Before imposing any nutritional intervention. A key component of a horse management program should be estimating body weight. As well as body condition on a regular basis.

To gain, lose or maintain body weight, monitoring the weight of a horse… would allow the owner to accurately measure the amount of feed needed by the horse. As well as show the amount of weight loss or gain over a period of time. You can measure the body weight using three simple techniques. The most accurate way of estimating weight is a large livestock scale. But using a weight tape is also okay.

If you have no weight tape, you can use a basic measurement tape. Measure the girth of the heart. Then measure the length of the horse starting from the shoulder’s point to the point of the buttock.

What’s the next step?

The first step in figuring out the reason of weight loss is to know exactly how much your horse eats. For a while, this could mean separating it from the other horses. Deworming medicine should be administered. And you should not overlook the value of water in the diet of your horse.

There are some tips on what to feed your lean horse. If there is no change after feed increase and making sure that the horse is dewormed… you will need to consult a veterinarian about inspecting the teeth of the horse.

If there is still no change after dental work, the veterinarian will take blood tests. This is to ensure there is no illness or disease causing weight loss.

Strategies for Your Horse to Gain Weight

When the cause of persistent weight loss has been known… it is time to start implementing feeding methods to increase the weight. The 2007 National Specifications for Horses indicated that… improving the score of the body condition by 1 unit (based on a 500 kg horse) requires 16 to 20 kg of gain.

By adding extra calories to the diet, we can reach this measure of weight gain in more or less 90 days. When feeding to gain weight, caution should also be taken. To not cause digestive disturbances with the increase of feed intake. Then the question becomes: “What should I feed my horse to gain weight?”

First of all, the quantity and quality of forage available for the horse must be increased. The addition of lucerne hay, chaff and/or HYGAIN MICRBEET ®… can improve the diet’s calorie content. Then, we will begin to add commercial feeds to the diet. This must be done in the right way so that no digestive disruption is being induced.

Then, with a fat supplement such as HYGAIN ® RBO ® and HYGAIN TRU GAIN ®, we can top the grain. Or progressively turn the horse to a high fat feed concentrate. Like HYGAIN ® SHOWTORQUE ® or HYGAIN ® GROTORQUE ®.

Allison Price
Allison Price

I’m Allison, born and raised in San Diego California, the earliest memory I have with horses was at my grandfather’s farm. I used to sit at the stable as a kid and hang out with my Papa while he was training the horses. When I was invited to watch a horse riding competition, I got so fascinated with riding!