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THE LAMINITIS HORSE – What is laminitis, and what can we do about it?

June 12, 2018

If you have ever called your horse an “easy keeper,” wondered when your gelding was going to foal or joked about how your horse gains weight off air, then keep reading, friends, because what I am about to tell you may be crucial to your horse’s health. Those horses described above may be easy on the pocketbook feed-wise but they may end up giving you more trouble in the long run. How, you ask? Many of these horses may have an endocrine or metabolic disorder, such as Equine Metabolic Syndrome (EMS) or insulin resistance (IR). These horses are the poster-children for classic springtime “the grass is green so I let my horse out to graze, but now my horse can’t walk” founder. That’s right, the big “F” word in the veterinary world. 

Laminitis, or founder, affects approximately 15% of the equine population in the United States. That is more than 1 in every 7 horses. That statistic is even worse if you own one of the “predisposed breeds” (Ponies, Arabians, Quarter horses, Paints, and Morgans; aka those “easy keepers”). Every year equine veterinarians all over the world diagnose, treat and, in a lot of cases, euthanize horses afflicted by this devastating disease. In fact, it is the  SECOND  leading cause of death in horses in the United States- second only to colic. This disease is indiscriminate – famous horses like Secretariat, the renowned racehorse who won the Triple Crown in 1973; the 2006 Kentucky Derby winner, Barbaro, who shattered his leg during the Preakness Stakes; and Colonels Smoking Gun (Gunner), the legendary reining stallion, were all euthanized because of laminitis. It does not matter the breeding or the cost of the horse. What matters is they all have hooves.

If you’ve spent much time around horses, you know the truth behind the saying “no hoof, no horse.” Honestly, I have no idea how they put so much stress and strain on those tiny legs and hooves. Do you realize they are putting 1000 plus pounds on their middle fingers? That’s right, they are literally flipping you the bird all day, every day. Horses are pretty amazing animals, but their anatomical design is sometimes less than desirable. In order for us to explore what YOU can do to help prevent some cases of laminitis in our bird flipping friends, it is important to know some basic facts about this disease. So bear with me as we peruse through some quick laminitis facts! (YAY, LEARNING!)

The Disease:

The pathology of this disease is most certainly complex, so I won’t bore you with all of the details, but here are the important take home messages about this disease process:

1. Laminitis simply means “inflammation of the laminae.” The laminae is highly vascularized tissue that connects the coffin bone (kind of a dark anatomical name, don’t you think?) to the hoof wall and keeps the boney column or skeleton suspended.

Figure 2: Anatomy of the Hoof

2. Blood flow is increased to the laminae because of some inciting cause (we will talk about these causes soon!). This can be felt by palpating “bounding” digital pulses on the back of the fetlocks.

3. Laminitis is considerably painful due in part to the horse’s unique anatomy: the inflammation causes tissues to swell, but there is no room for tissue expansion because of the hard hoof capsule, causing more and more pressure within the structure, resulting in even more pain.

4. The laminae acts like Velcro: there are 2 pieces with finger-like projections that stick together to help support the coffin bone and keep everything in place. Chronic or severe inflammation of these tissues causes a disruption of these structures. And the Velcro fails.

Figure 3a: Normal hoof. Coffin bone and hoof wall follow the same angles.

5. When the laminae is disrupted it can cause sinking and rotation of the coffin bone.

6. While laminitis and founder are used interchangeably, the term founder is usually reserved for those cases where there is rotation or displacement of the coffin bone secondary to laminitis.

7. The degree to which the coffin bone sinks and rotates is a huge prognostic indicator. Sadly, in some cases, the coffin bone drops and rotates so much it can go through the sole or bottom of the hoof.

Common causes of laminitis:

Unfortunately there are a lot of possible causes of laminitis, but the more common causes we see include: systemic illness (colic, fever, infection, etc.), grain overload, chronic limb overload (bearing more weight on the opposite limb due to a fracture, injury or other cause of non-weight bearing lameness), and metabolic conditions (Equine Metabolic Syndrome/Insulin Resistance, Pars Pituitary Intermedia Dysfunction also known as Cushing’s disease).

In this blog I am going to focus on those  metabolic conditions  that contribute to laminitis. Equine metabolic syndrome (EMS) is a common condition in horses where they have an insulin resistance or dysregulation. They store fat, and lots of it, in areas on their body such as their neck/crest, withers, and the point of their tail. Fun fact: the top of the neck should not be flopping around all willy-nilly like as they frolic toward you to get their evening grain. Nor should your horse collect rain water on its back. As a veterinarian, it is my job to distinguish whether these horses are overweight due to excess calorie intake and decreased exercise or if it is due to a medical condition.

The good news is if your horse is diagnosed with EMS, treatment usually does not entail expensive medication or ongoing diagnostic tests. Treatment is primarily geared toward dietary change and weight loss. A diet change means NO alfalfa, NO grain, and NO grazing. Yeah, basically Easy Keeper Ed gets to eat a bland, boring diet of grass hay his entire life. But I promise it is for the best. Once we decrease the amount of nonstructural carbohydrates (NSCs) in your horse’s diet, the less likely he/she will be to founder. You can get your hay tested to ensure whatever you are feeding Easy Keeper Ed has a low NSC content (goal: less than 10-12%).

Another common metabolic disorder seen in older horses is Equine Cushing’s disease (now called Pars Pituitary Intermedia Dysfunction, or PPID – because we love long, difficult names and acronyms in Veterinary Medicine). This disease is basically caused by small benign tumors that develop on a specific part of the brain, causing an overproduction of steroid hormones. These horses usually have long winter coats that don’t shed out normally, lose weight, drink a lot of water (and subsequently urinate a lot), can be lethargic, have muscle or weight loss, or be more prone to infections. The majority of PPID horses are older than 15 years of age and clinical signs are usually variable and have a slow onset. While we don’t know the exact correlation, we do find a lot of horses that have EMS may be predisposed to PPID. Those horses diagnosed with PPID will need to be on a medication for the rest of their lives to help manage this disease.

The majority of horses I diagnose EMS or PPID aren’t coming in to see me because they are overweight or they have a longer hair coat than normal. Unfortunately most horses won’t see a veterinarian until they have already foundered. My hope is after reading this article owners will be more informed about the possible clinical signs of these metabolic conditions and seek medical attention BEFORE disaster strikes. Even if it saves one horse and owner from having to go through what I believe is one of the worst diseases a horse can get, it’ll all be worth it.

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