Hay Belly in Horses

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 gelding suddenly appears pregnant (although not physically possible), he may be suffering from hay belly. Don’t be embarrassed—your horse hasn't gained the "Freshman 15." But he could have a nutritional imbalance from grazing on too many grasses. And while a distended abdomen may look alarming on a horse, balancing out its diet will get it back on track.

What Is Hay Belly?

The term "hay belly" refers to the physical appearance of a distended abdomen on a horse. 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. It can also make mares look like they are in late pregnancy.

Symptoms of Hay Belly in Horses

Hay belly is not a sudden change, but is rather a physical appearance in response to a horse's diet and perhaps lack of fitness over time. A horse may also develop a lackluster coat and may appear to be in poor condition. However, this isn’t always the case. Hay belly can occur in horses of any age, so if you notice a degraded appearance of your once-vibrant horse, contact your veterinarian for a correct diagnosis. A distended abdomen can also be a sign of other more serious health issues such as a heavy parasitic infection or endocrine disease such as Cushing's disease.

Causes of Hay Belly

Generally, hay belly is caused by poor nutrition. More specifically, it is typically seen when a horse is fed poor-quality forage, such as very stemmy, old hay, and not enough protein. This shifts the fermentation process in the horse's hind gut to produce excess gas. It also causes the horse to lose muscle tone over his topline, particularly if he's not being exercised regularly.


If your horse appears to have a hay belly, consult your veterinarian for 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 concentrate feed. Or, you may simply need to change your horse's hay altogether, switching to a higher quality forage. Having your hay's nutritional content analyzed may help you make decisions about what forage to use. Remember to make any changes in your horse's diet slowly.

Over a period of several weeks to months of tweaks to your horse's diet, you should notice your horse's belly starting to retract. Maintaining a quality diet, especially in the winter when snow is on the ground, is the key to keeping your horse in sound condition. 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.

When It's Not Hay Belly

Not all big bellies are hay belly. A horse's distended abdomen could be attributed to Cushing’s disease, or other metabolic disease or organ failure. Horses who crib bite (a behavioral disorder) often have distended abdomens related to colic or stomach ulcers. And a horse that looks unhealthy, yet has a large belly, may have a severe parasite load causing bloating. Lastly, mares who have delivered several foals, as well as older horses, may appear to have a hay belly due to a stretched slackness of the muscles in the back meant to support the stomach.

Pay special attention to foals with a large tummy. If the foal is in poor health overall, parasite control may be needed. Also, foals need carefully balanced nutrition throughout their growing stages. But don't overfeed them, as this can cause other health problems. Talk to your veterinarian for specific nutrition advice for growing horses.

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 -- make sure your horse's diet fits his individual needs. Remember, 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. And while horses spend the bulk of their time grazing, 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
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  1. Q&A: Thin Mare Possesses Hay BellyKentucky Equine Research, 2020

  2. Overweight HorseAmerican Association of Equine Practitioners, 2020

  3. Myths About Hay SelectionUniversity of Kentucky's College of Agriculture, Food, and Environment, 2020