By Dr. Lydia F. Gray, posted September 2022

When people think of laminitis, they probably think of a pony that was turned out onto lush spring grass too quickly. Experts now know that’s a very specific – and important -- kind of laminitis so they’ve given it a special name: pasture-associated laminitis or PAL. Because there are several teams of veterinarians and research scientists around the world studying laminitis and they’re still figuring things out, there are a couple of other names in use:

Endocrinopathic Laminitis or EL
pronounced “in-doe-crin-oe-PATH-ick”)
“endocrine” means hormones, and “pathic” means caused by
Hyperinsulinemia-Associated Laminitis or HAL
pronounced “high-per-inn-sull-inn-EE-me-uh”
“hyper” means too high, “insulin” is a hormone, and “emia” means in-the-blood
Don’t be intimidated by these long, hard-to-pronounce names! They all just mean “metabolic” laminitis. When researchers all over the world are working on the same problem separately, they tend to use Latin. This way, when they communicate with each other or publish papers, they’re talking apples to apples. Getting the terminology right, and getting it into mainstream use, is all part of the battle.

Some experts combine all three names into one: Pasture and Endocrinopathy-Associated Laminitis (PEAL). They do this to make it clear that pasture -- plus a disorder of the endocrine (hormone) system -- is what leads to laminitis in the vast majority of cases. In fact, PEAL is thought to be responsible for 90% of all laminitis cases in horses.

 

Approximately 10% of laminitis is due to another broad category: a bacterial infection or bacterial overgrowth somewhere in the body. Some vets call this Sepsis-Associated Laminitis while others call it Systemic Inflammatory Response Syndrome or SIRS. The bottom line is that toxins released from bacteria trigger an exaggerated inflammatory response from the body and together this causes damage to the lamina.

Examples of laminitis from this category include:

Grain overload
Severe diarrhea or colitis (i.e. inflammation of the colon)
Uterine infection from not passing the afterbirth, aka retained placenta
Complications from pneumonia
Toxins including black walnut, hoary alyssum, and endotoxin from fescue
Body-wide (systemic) sickness such as Strangles, Potomac Horse Fever, Lyme Disease
There is a third cause of laminitis, but it’s very rare. Some people call it Supporting-Limb Laminitis and others call it Standing-Limb Laminitis, but it occurs when one leg takes more weight temporarily because of a lameness or injury and that extra weight damages the lamina. “Road Founder” would fall in this category, as would other things that disturb the natural movement and structure of the hoof, such as a club foot or the opposite, a long toe/low heel.

Read the third article in the Laminitis series – “What do Sugars and Starches Have to do with Laminitis?” – and learn about the role of simple carbohydrates in this condition. Read the first article in the series – “What is Laminitis in Horses?”.

By Dr. Lydia F. Gray, posted September 2022

This third article in the Laminitis series explains the role that simple carbohydrates play in this condition. (If you haven’t already read the first two articles, “What is Laminitis in Horses” and “Laminitis Has More Than One Cause,” you may want to check them out first).

In part two, it was explained that “metabolic” laminitis is responsible for 90% of all cases of laminitis in horses. It was also pointed out that metabolic laminitis has several names in the scientific literature:

Endocrinopathic Laminitis (EL)
Hyperinsulinemia-Associated Laminitis (HAL)
Pasture and Endocrinopathy-Associated Laminitis (PEAL)
To better understand metabolic laminitis, here are some definitions of commonly used words when talking about it:

Insulin – a hormone produced by the pancreas in response to a meal that controls the amount of glucose (sugar) in the blood by moving it into cells where it can be used by the body for energy or stored for later use.

Insulin Resistance (IR) – failure of the body to respond properly to insulin

Hyperinsulinemia (HI) – abnormally high levels of insulin in the blood, which is a risk factor for laminitis

Insulin Dysregulation (ID) – a newer term used to describe horses with high levels of insulin in the blood (hyperinsulinemia), regardless of whether it’s caused by insulin resistance or another reason.

Equine Metabolic Syndrome (EMS) – a collection of risk factors such as Insulin Dysregulation, obesity, and/or “lumpy fat” that increases the risk of laminitis in horses. EMS results from the “perfect storm” of genetics and environment, in which a breed prone to this condition is fed a diet high in sugars and starches and receives little to no exercise.

Regional Adiposity – the buildup of lumpy fat (adipose tissue) in certain areas, such as the so-called “cresty neck,” also behind the shoulder, at the tailhead, above the eye, and in the sheath or mammary gland region

Cushing’s Disease/Pituitary Pars Intermedia Dysfunction (PPID) – a slowly progressive endocrine disease common in older horses, PPID happens when the hypothalamus (a part of the brain) gradually degenerates over time and stops sending signals to the pituitary gland (a different part of the brain). This leads to unchecked growth and activity of the pituitary gland causing a number of compounds to be produced, such as ACTH, which is what veterinarians measure in the blood to diagnose Cushing’s Disease. Because Cushing’s can also trigger laminitis, when horses are tested for Cushing’s they should also be tested for insulin issues. Likewise, horses with insulin issues should also be tested for Cushing’s.

Since an abnormally high level of insulin in the blood is the underlying issue for PEAL, it makes sense that preventing insulin from getting too high could be an important way to help avoid laminitis. So what causes insulin levels to increase in the first place?

Earlier, insulin was defined as a hormone that is released in response to a meal containing sugar (or starch, since this is broken down by the GI tract into simple sugars). The more sugar that is eaten, the more insulin that is produced. The less sugar that is eaten, the less sugar that is produced. People with diabetes may be familiar with this explanation because their disease has to do with high blood sugar as well. In horses then, one way to help prevent hyperinsulinemia and possibly Hyperinsulinemia-Associated Laminitis is to feed a low-sugar, low-starch diet.

That may be easier said than done, since the horse community has been conditioned to think that horses “need” grain (which is high in sugars and starches) and that our horses will love us more if we give them treats, many of which are also sugar- and starch-heavy. Then there’s the commonly held belief that ‘all horses should eat grass,’ i.e. that modern grass is the natural food of horses.

For some practical ways to lower sugar and starch intake in horses, read the fourth article in the Laminitis series: “How to Reduce Sugars and Starches in the Horse’s Diet.”

By Dr. Lydia F. Gray, posted September 2022

This is the fourth and final article in the Laminitis series. To get the most out of it, we suggest reading the first three articles before tackling this one:

“What is Laminitis in Horses?”
“Laminitis Has More Than One Cause”
“What do Sugars and Starches Have to do with Laminitis?”

For a horse prone to or that has already had a bout of metabolic laminitis, step one is working with a veterinarian to come up with a complete plan for that individual. Proper diet, controlled exercise, plenty of turnout, and other management “best practices” should all be discussed. At the same time, owners should make sure they know how to evaluate Body Condition Score, Cresty Neck Score, and body weight.

Note that horses having an acute laminitic episode may be put on a stricter diet temporarily Exercise may also have to wait. Recovered and at-risk horses can usually be put on a less strict maintenance diet and begin a controlled workout program right away.

Often the first recommendation for reducing sugars and starches in the diet is to remove grain. This means no cereal grain (oats, corn, wheat, barley), no fortified grain in a bag, and no senior or complete feed, especially if it has molasses in it. Replace the protein, minerals, and vitamins with either a low sugar/starch ration balancer or a multi-vitamin paired with an amino acid supplement.

Another source of unnecessary sugars and starches is treats. Sugar cubes and peppermints are off-limits. Other treats –such as carrots and apples - should be given in moderation. Only commercial treats with guaranteed low levels of starch and sugar are appropriate. Hint: if molasses, corn, dextrose, or maltodextrin are listed on the label, chances are it’s not a low NSC product.

Focus on Forage
As important as reducing or removing grain and treats is, forage makes up the largest portion of a horse’s diet so efforts should focus on making hay and grass as safe as possible. Unfortunately, there is no safe pasture in acute laminitis situations, so horses with current sore feet need to be in a dry lot or otherwise restricted from fresh grass. Recovered and at-risk horses may be able to enjoy pasture under certain conditions: early morning, in the shade, with a muzzle. Grass that is stressed from cold temps overnight, drought, overgrazing, poor soil conditions, and other factors should not be grazed by horses prone to laminitis. Young growths of grass are particularly dangerous so spring grazing should be monitored carefully or better yet, omitted altogether.

Since hay will make up all or almost all of the diet for “carbohydrate-intolerant horses,” it’s important to understand the advice and the options for selecting and feeding hay. Most experts recommend feeding 1.5-2% of the horse’s body weight in grass hay. This works out to 15 to 20 pounds of hay spread out over the course of a day for a 1,000 pound horse. In addition, the hay should be less than 10-12% NSC when analyzed by a lab.

NSC stands for Non-Structural Carbohydrates and is a popular term among vets, nutritionists, farriers, and horse owners. However, it’s one of those terms that’s not quite used 100% accurately.

To set the record straight, here are the facts:

Another name for sugars in hay is ESC or Ethanol-Soluble Carbohydrates.
The combination of sugars (ESC) and fructans (a specific type of sugar), is called WSC or Water-Soluble Carbohydrates.
When you combine WSC with fructans, you get NSC, or Non-Structural Carbohydrates .
However, fructans are unlikely to cause laminitis, so we only really need to talk about the sugars and starches in hay, or ESC plus starch.
Unfortunately, neither “ESC plus starch” and “sugars and starches” roll off the tongue like “NSC,” which is probably why “NSC” stuck as the preferred term.
Here’s the problem: hay that would be perfectly fine for a carbohydrate-intolerant horse is labeled “unsafe” because the NSC % is used as a threshold and not the more correct “ESC plus starch” figures
The sugar and starch levels in hay depend on many factors, such as the species of hay (timothy, orchardgrass, brome, coastal Bermuda, fescue, others), the maturity at cutting, how long it dried in the field before baling, and even the time of day it was cut.

One way to make sure that forage is low sugar/starch at each and every feeding is to buy chopped, cubed, or pelleted hay in a bag with guaranteed maximum levels. While buying bags of forage can be pricey – and may not be available in all parts of the country – it does assure that the diet doesn’t change for horses at high risk of laminitis. This is especially important in the fall when horses with endocrine and metabolic disorders experience seasonal issues.

The best and only way to know how much sugars and starches are in hay is to have it analyzed. If it’s not possible to find hay that is naturally less than 10-12% NSC, one option is to soak the hay in water to reduce the soluble carbohydrates. A team of scientists from the University of Minnesota showed that soaking orchardgrass hay in warm or cold water for 15, 30, or 60 minutes lowered the levels of sugars and starches down into the range recommended for horses with laminitis (Martinson, 2012). This traditionally wet, messy, and labor-intensive process is becoming more reliable and convenient with modern hay soaking units where the soak and drain times can be programmed to prevent over or under soaking.

Series Summary
Laminitis is a serious hoof condition in horses that veterinarians and researchers are learning more about every day. This long-standing term is based on the thinking that inflammation plays a key role in lamina damage. However, the vast majority (90%) of episodes are due to the combination of the hormone insulin, a high sugar and starch diet, and the lack of exercise in horses and ponies whose genes put them at-risk.

With current research linking high blood levels of insulin (hyperinsulinemia) to laminitis, there are now practical ways to help prevent horses from developing this potentially career-ending and life-threatening condition. The sugars and starches can be reduced in the diet by soaking hay, limiting grass, and not feeding grain. In horses that are sound, exercise can be added or increased. A horse or pony’s body condition score, cresty neck score, and body weight can be regularly assessed. And owners can work with their veterinarian to monitor blood insulin and glucose levels as well as the presence of other diseases and conditions that may complicate the situation. Laminitis will probably always be around, but now science has given owners a better understanding of what puts their horses at risk and practical methods to reduce the threat.