Hay Belly in Horses

Causes, Treatment, and Prevention

Three Welsh mountain ponies (Equus caballus) in a field, including chestnut coloured pregnant mare and foal, and grey pony
Bob Langrish / Getty Images

If your horse develops a big, sagging belly but hasn't gained weight on the rest of its frame, it may be suffering from hay belly. This is a condition of gas accumulation in the gut that indicates a nutritional imbalance from eating poor-quality hay. While a distended abdomen may look alarming, hay belly is a condition that is treatable by improving the nutrient content of a horse's diet.

What Is Hay Belly?

The term "hay belly" refers to a bloated gut from the accumulation of gas. The belly area appears pendulous, sticking out at the sides and hanging down low. Hay belly may, somewhat counter-intuitively, make a horse look underweight, with protruding ribs and a lack of padding and muscles along the neck, withers, and haunches.

Symptoms of Hay Belly in Horses

Hay belly is not a sudden change, but rather a gradual enlargement of a horse's midsection in response to diet and perhaps lack of fitness over time. Symptoms may be vague but generally accompany a bloated appearance.


  • Bloated/distended abdomen
  • Sagging belly
  • Lackluster coat
  • Poor condition

The telltale sign of hay belly is a disproportionately large abdomen on a normal or thin horse. The belly will sag and bulge out to the sides.

In addition to the obvious distention of the abdomen, a horse may also develop a lackluster coat and may appear to be declining in condition as it loses muscle tone over its topline.

Hay belly can occur in horses of any age, so if you notice a big belly and degraded appearance in your once-vibrant horse, contact your veterinarian for a diagnosis.

Causes of Hay Belly

Generally, hay belly is caused by poor nutrition. More specifically, it happens when:

  • A horse is fed poor-quality forage, such as old hay or hay that lacks adequate protein.
  • The diet lacks a grain supplement.
  • A horse overeats to compensate for the lack of nutrients in its feed.
  • Excessive consumption of high fiber and low protein feed alters the fermentation process in the horse's hind gut, producing excess gas.
  • Exercise is insufficient to help maintain healthy digestion and overall muscle tone.

Diagnosing Hay Belly in Horses

If your horse has a bloated belly, consult your veterinarian. A distended abdomen can be a sign of weight gain or other serious health issues such as a heavy parasitic infection or endocrine dysfunction (Cushing's disease). These conditions must be ruled out to definitively diagnose hay belly.


Your veterinarian can offer advice on a high-quality diet protocol. If your horse is on pasture, your vet may suggest supplementing its grazing with nutrient-dense, high-quality hay and may also suggest a protein supplement in the form of a concentrated feed.

You may need to change your horse's hay source, switching to a higher-quality forage. Having your hay's nutritional content analyzed may help you make decisions about its quality. Remember to make any changes in your horse's diet slowly to avoid further digestive stress.

Maintaining a quality diet, especially in the winter when snow is on the ground, is the key to keeping your horse in sound condition.

Prognosis for Horses with Hay Belly

Over several weeks to months of tweaks to your horse's diet, you should notice your horse's belly starting to retract and its condition improving.

Make sure to communicate your progress with your vet to assure you're on the right track. Regular assessment of your horse's body condition score and body weight using a weight tape will help you objectively measure your horse's progress.

How to Prevent Hay Belly

Proper nutrition is the first step to maintaining the health of your horse. Not all horses should be fed the same way, so make sure your horse's diet fits its individual needs.

Even if your pasture appears green and flourishing, your grass may not meet your horse's needs once dry weather sets in and environmental conditions change. A balanced supplement or concentrate may be given to assure they're getting the vitamins, minerals, proteins, and carbohydrates they need.

Regular exercise also helps prevents the appearance of a sagging torso. When a horse is physically fit, the muscles surrounding the belly and along the back are well toned. This is especially important in broodmares and older horses. A break from motherhood and regular riding helps build the muscles that support the stomach while contributing to proper digestion and healthy joints.

If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.
Article Sources
The Spruce Pets uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Q&A: Thin Mare Possesses Hay Belly. Kentucky Equine Research.

  2. Overweight Horse. American Association of Equine Practitioners.

  3. Myths About Hay Selection. University of Kentucky's College of Agriculture, Food, and Environment.