Learn How Laminitis Changes With the Seasons

This article was originally published October 4th, 2013, and was updated on October 31st, 2024.

The sky is so blue! The air is so crisp! The woods are ablaze with color, and the bugs are finally gone! But when you bring in your horse from the pasture, he balks on the lead line and shuffles his feet. He seems to say “ouch!” with each tentative step.

Laminitis in Fall?

The last time your horse’s feet were sore was in April a few years ago, when he ate too much spring grass. But this can’t be laminitis again. It’s October. Laminitis is a springtime disease. Or is it?

Between 2 and 7 percent of all horses in this country have experienced laminitis in some form, researchers say; USDA statistics show that laminitis was reported on 13 percent of horse properties. Of that group, about 5 percent didn’t survive.

Here, you’ll find insight into how equine laminitis seems to change with the seasons, and why it’s especially important to understand the risks that come in the fall.

Then you’ll learn how to reduce your horse’s risk, and what to do if he starts showing signs of laminitis any time of the year.

Using this information, you’ll be able to understand more about your horse’s hormone levels, then schedule blood tests, adjust feed, and evaluate grazing accordingly.

Your reward will be a healthy and happy horse whose feet won’t let him down.

What is Laminitis?

Laminitis is the most serious disease of the equine foot and causes pathological changes in anatomy that lead to long-lasting, crippling changes in function (termed chronic laminitis or founder). It’s the second-biggest killer of horses after colic.

A horse has laminitis when the foot’s lamina, the connecting fibers between hoof wall and bone, suddenly fail. Without the bone properly attached to the inside of the hoof, the horse’s weight and the forces of locomotion drive the bone down into the hoof capsule. Arteries and veins are sheared and crushed, and the blood-delivery system to the coronet and sole is damaged. This results in unrelenting foot pain and lameness.

Laminitis’ clinical signs, the extent and severity of the condition and the response to therapy vary, making treatment and accurate prognosis difficult, notes Chris Pollitt, PhD, MRCVS, of the Australian Equine Laminitis Research Unit.

Severe damage to the hoof can occur within a few hours. The severity and extent of this initial damage is the single most important factor influencing the final outcome.

[READ: 5 Articles to Understand Hoof Health]

Risk Factors

Laminitis may strike at anytime and for many reasons. What we’ve always called “grass laminitis” is the most common form of the condition and often recurs.

It strikes most often in spring and fall, but often coincides with the end of long periods of drought or extreme weather that affect the grass’ lifecycle, regardless of what it says on the calendar.

More factors than just grass increase the risk. Here’s a rundown.

Hormonal problems

Disruption of a horse’s ability to produce or regulate specific hormones can lead to laminitis. An estimated 90 percent of laminitis cases can be traced to hormonal problems in horses; “grass laminitis” occurs in horses with imbalanced hormones.

Luckily, veterinary tests can measure your horse’s hormone levels for evidence of Equine Metabolic Syndrome, a disorder of the hormone insulin (“insulin resistance”), or Pituitary Pars Intermedia Dysfunction, formerly called Equine Cushing’s Disease.

PPID tests measure adrenocorticotrophic hormone (known as ACTH) from the pituitary gland. Some PPID horses may also have insulin level problems; your horse should have both tests.

Obesity

Seasonal laminitis is especially problematic for horses we call easy keepers. They tend to keep on weight regardless of how little grain they’re fed. However, not all easy keepers or obese horses have EMS, and not all horses with EMS are obese. Some may not look fat at first glance; many have pads of fat only on their shoulders and at the base of their tails, and their necks have overdeveloped crests.

“Obesity is the single greatest predisposing cause of laminitis in pleasure horses,” says Donald Walsh, DVM, of Homestead Animal Hospital in Villa Ridge, Missouri, a pioneer of laminitis prevention through the laminitis research organization Animal Health Foundation (www.ahf-laminitis.org).

“Other risk factors take on a greater importance when they show up in a horse that’s obese, as well. Based on my experience observing laminitic horses over the past 46 years in veterinary practice, I believe that obesity leads to the development of weakened laminae, and changes in the growth pattern of the feet.”

Abnormal hoof wall

A ridged hoof wall, marked with raised “fever rings” or changes in hoof-growth pattern, is a distinct warning sign. Small dots of dark blood or bands of redness seen in the white line during trimming are also signs that some laminitis-related damage occurred in the past.

Springtime bouts

Most horses that suffer from seasonal laminitis seem to have bouts of it in the springtime when the pastures come back to life after a winter of dormancy.

Veterinarians, such as Dr. Walsh, think that without a hormonal problem, lush grass isn’t a health risk in itself. But once a horse has had laminitis, the disease often strikes again if he isn’t carefully managed.

This recurrence happens because such a horse is

genetically prone to develop insulin resistance, especially if he’s overweight; and the previous laminitis left his feet damaged, weak, and prone to new bouts of the disease.

Classic factors

The classic non-hormonal causes of laminitis still exist. These include grain overload, retained placenta in mares, drug reactions, high fevers, and high stress. Support-limb laminitis is a problem in horses with leg injuries.

Remember that horses can develop laminitis for reasons other than just grazing on grass in the spring and fall.