Bright green grass is one of the signs of spring, but all that green is also a red flag for hoof-care professionals. It means it’s time to remind your clients of an increased danger of certain forms of laminitis, as well as keeping an eye peeled for the early warning signs of the disease.

Unfortunately, laminitis is a condition that hoof-care professionals usually encounter after a horse already has begun suffering from it. If untreated, laminitis can lead to a breakdown of the laminae that form the connection between the hoof wall and inner structures of the hoof, such as P3. This results in an interruption of the normal blood supply, pain and downward rotation of P3, putting still more pressure on the sole of the foot. In extreme cases, horses are often put down.

Heading off laminitis before it occurs is preferable to even the most successful of treatments, so it makes sense for farriers to learn as much as they can about the disease and its causes, and to share that information with their clients.

Important topics that horse owners need to be aware of are why spring grass is associated with laminitis, whether they have horses that appear particularly at risk and what kind of diet and other precautions they can take to head off the disease before it occurs.

While research has linked laminitis to a number of different causes (see “Causes of Laminitis” below), in the spring of the year, the biggest concern is horses whose diet is suddenly enhanced with spring grass. One survey concluded that access to lush pasture might have been responsible for almost half the cases of laminitis.¹

Stay Off the Grass

“Grass founder” is a term often associated with the occurrence of springtime laminitis. While laminitis can occur year-round, grass founder is believed to be more common when pasture grasses have higher levels of fructans in the spring and fall. These sugars are thought to be a trigger that sets off a cascade of events that lead to laminitis, particularly in certain horses.

According to information posted by the Animal Health Foundation, fructan levels have been found to be highest in the spring and again in autumn. These high levels are associated with a combination of cold nights and warm, sunshiny days. These sugars have been found to be particularly high in the early morning hours after cold nights, but are generally higher than normal throughout the spring season.

During early spring, fructan levels are likely to remain high throughout the day because the sugars are not used by the grasses due to low metabolic rates during the cold nights. That means grazing should be avoided throughout early spring.

In later spring, when warmer nights become common, grazing probably can be allowed safely in later morning hours and afternoons. Grazing is safest in mid-summer, after grasses have passed their flowering stage. It becomes dangerous again in the fall when cold nights and even light frosts can cause fructan levels to spike.

Obviously, spring comes to different areas at different times, so it’s important to be aware of the conditions in your own area.

Veterinarian Donald Walsh, foun­der of the Animal Health Foun­dation, thinks that “grass laminitis” is a relatively new and human-caused phenomena.

“The most interesting thing to me in looking at grass laminitis is that it was not reported in U.S. literature until the 1942 Yearbook of Agriculture,” he notes. “So the farming practices and husbandry practices since 1920 have developed this endocrine form of this disease.”

Modern horses are much more likely to be overfed and under-exercised than were the working horses of earlier eras and research repeatedly has linked obesity to laminitis.

The makeup of pasture grasses also is a contributing factor. The Animal Health Foundation puts it this way.

“What we know about pasture grass is that the lower the level of non-structural carbohydrates (NSC), the safer the grass. The warm-season or C4 grasses (i.e., native grasses, prairie grasses and Bermuda grasses) generally have lower levels of NSC. The cool-season or C3 grasses, which include the most common type of grass hay (i.e., timothy, orchard grass, brome, fescue, clover), have higher levels on non-structural carbohydrates.”

It’s also important to remind horse owners that it isn’t the bright green color of spring grass that they need to be aware of. It is the content of the grass, particularly fructans and other non-structural carbohydrates that create the problem. Even dry brown and yellow grasses have been found to contain high NSC6 levels under certain conditions.

Kathryn Watts, director of research at the Rocky Mountain Research and Consulting Center, has conducted extensive research on the sugar content of grass, as well as hay, and has consistently found that the sugar content of grass hay does not correlate with color, texture, the amount of stem or age. She emphasizes the importance of having hay or grass properly tested. Her website also offers specific methods and tips for gathering pasture and hay samples for effective testing.

This horse displays the cresty neck associated with Cushing’s disease and the subsequent development of laminitis.

Horses at High Risk

Research indicates that certain horses are at higher risk of the endocrine form of laminitis. This is particularly true of horses with equine metabolic syndrome (EMS) or Cushing’s disease.

EMS and Cushing’s are similar, but as a general rule, Cushing’s is more likely to occur in older horses, generally at least 15 years of age.²

In Cushing’s disease (more accurately called pituitary pars intermedia dysfunction or PPID), aging affects struc­tures in the pituitary gland re­sulting in an overproduction of ad­re­no­corticotropic hormone (ACTH) and cor­ti­sol. This results in a shaggy coat that the horse doesn’t shed even in warm weather. There is also sweating and weight loss, increased thirst and urinations.

EMS horses, on the other hand, usually are younger and will be overweight, with a cresty neck and fat deposits along the neck and spine. They’re the horses often referred to as “easy keepers.” EMS is sometimes used to describe any horse or pony with chronic insulin resistance that does not have Cushing’s disease.³

Some horses seem to have a genetic disposition toward this condition. Researchers theorize that these horses have a “thrifty gene” that was developed to help horses survive in harsh conditions where there was little food and water. But in modern environments, with plenty of forage and even grain available, that once life-saving thrifty gene instead becomes life threatening. High carbohydrate intake results in a high level of insulin in EMS horses and high insulin levels are believed to cause laminitis in horses and ponies.⁴

One of the difficulties of dealing with grass founder, is that horses that do not carry the “thrifty gene” might be able to eat their fill of pasture grass with little or no ill effects, while the at-risk horse develops laminitis after grazing on the same pasture at the same time.

EMS horses usually display insulin resistance. High insulin levels are believed to cause laminitis in horses and ponies. When these horses are allowed to graze on lush pasture, it results in increased levels of glucose in the bloodstream. In normal horses, this results in a slight elevation of insulin until glucose levels normalize. But in EMS horses, much higher levels of insulin are released, which can set off a series of changes that lead to laminitis.⁵

Diagnostic tests for Cushing’s are often run at the same time as EMS, particularly when the horse is older. When Cushing’s is present, ACTH is elevated.

Walsh says farriers should keep an eye out for abnormal stretching of the dorsal laminae, resulting in growth rings and seedy toe, often accompanied by hemorrhages.

“If farriers see this, they need to tell the owner to get the horse’s hormone levels for insulin and ACTH run to properly diagnose the condition,” he says.

One problem with testing is that the change in hormone levels may not be apparent until after the cascade of events that leads to laminitis has already started. That’s another reason to carefully monitor the diet of horses that exhibit the signs of EMS or that have a past history of grass founder episodes.

Diet Recommendations

With some EMS horses, heading off springtime laminitis can be a simple matter of restricting diet and increasing exercise. That obviously means restricting access to pastures known to contain grasses high in fructans and other non-structural carbohydrates, but it also means addressing other feeds, particularly those high in starch or sugar.

Obese horses should get a simple diet of hay and a vitamin/mineral mix. But remember that it is important to have the hay tested. Recommendations vary, but hay should have less than 12% of NSC content. While some people recommend soaking hay in cold water for 30 minutes to reduce sugar content, actual tests of water-soaked hay provide widely varying results, so Walsh suggests your clients be wary of relying on this method.⁶

As a general dietary guideline, the Animal Health Foundation suggests reducing grain intake and increasing roughage. The organization recommends removing corn and alfalfa from the diet.

While it’s important for your clients to increase exercise for EMS horses as part of controlling body weight and improving condition to prevent laminitis cases, caution must be taken once a laminitic incident has been detected. Exercise can cause additional damage to the already damaged structures within the foot. This can be particularly problematic if a horse has been administered pain-controlling drugs.

Don’t Wait, Call The Vet

It’s also important to stress to your clients that the first 24 hours after a laminitis onset are critical. Too often, by the time the symptoms are noticed, serious damage already has occurred. A veterinarian should be called as soon as the condition is suspected.

References

1. Mansmann R., King C., More About Grass Founder, American Association of American Practition­ers.
2. Zimmel D., Management of Equine Cushing’s Disease and Equine Metabolic Syndrome, University of Florida Extension.
3. Ibid.
4. Kritchevsky J., Overview of Equine Metabolic Syndrome, Merck Manual Veterinary Manual.
5. Ibid.
6. Zimmel D., Ibid.

March 2017 Issue Contents