Hot hooves, pounding digital pulses, a sawhorse stance, severe lameness; these are all signs of laminitis – one of the conditions most dreaded by horse owners, and for good reason! In severe cases, laminitis can result in permanent lameness and even lead to euthanasia.

Laminitis occurs when there is damage to the laminae of the hoof — where the hoof wall is connected to the coffin bone. It can occur in one or multiple hooves at the same time and by different mechanisms.

The separation can lead to permanent structural changes in the foot and lasting lameness. In rare cases, destabilization and rotation of the coffin bone can be so severe, the coffin bone actually ruptures through the sole of the hoof.

Researchers have learned that laminitis does not strike out of nowhere. Instead, there are often early warning signs and a prolonged subclinical phase that precede clinical laminitis. [1]

If you can learn to recognize these signs in your horse, then you greatly improve your chances of identifying and reversing this condition before it becomes severe and life-threatening.

How Laminitis Occurs

While laminitis was once considered to be a disease in and of itself, researchers now agree that it is a consequence associated with systemic conditions including endocrine disorders, sepsis or systemic inflammatory response syndrome (SIRS), toxins, and overloading of a hoof.

Laminitis associated with metabolic disease, also known as endocrinopathic laminitis is the most common presentation. Researchers believe that more than 90% of horses that develop laminitis have an underlying endocrine disease, that results in elevated insulin (hyperinsulinemia) usually Equine Metabolic Syndrome (EMS) or Cushing’s Disease. [2]

Specifically, insulin resistance and hyperinsulinemia alter blood flow mechanics to the foot. [2] These horses are more likely to suffer from laminitis if their diet is not properly controlled for less than 10% hydrolyzable carbohydrates (HC) (ESC + starch).

Pregnant mares become insulin resistant and may also develop laminitis even if they are not hyperinsulinemic when not pregnant. [10]

 

Healthy vs. Laminitic Horse Hoof | Mad Barn USAIllustration:

 

Endocrinopathic Laminitis

When horses ingest a large quantity of carbohydrates (starches and sugars), carbohydrate metabolism causes a spike in blood insulin.

Horses with metabolic disease and insulin resistance already have high baseline insulin levels, which means this spike can be even more profound. The resulting insulin crisis can lead to sudden and dramatic impaired blood flow to the feet. [2]

Hindgut acidosis

When horses ingest a large quantity of starch from grains or an experimentally high dose of fructan, the small intestine becomes overwhelmed and fructan or undigested starches spill over into the hindgut.

Starch and fructan fermentation in the hindgut increases hindgut acidity resulting in a shift in the microbial population of the hindgut as beneficial bacterial colonies begin to die off.

Components of these dead microbes, known as endotoxins, can be absorbed into the bloodstream (endotoxemia) and trigger a systemic inflammatory response. [3]

Sepsis-induced laminitis

Severe illness and endotoxemia triggers systemic inflammation, resulting in sepsis or systemic inflammatory response syndrome (SIRS) which can trigger laminitis.

Examples include cases of:

Nutritional toxicity

Acute laminitis can occur due to high intake of certain heavy metals including mercury. [11]

Known plants capable of inducing laminitis are black walnut tree , Hoary Alyssum, Red Oak acorn or buds, and avocados. Rattlesnake venom may also induce laminitis. [12]

Supporting Limb Laminitis

Supporting limb laminitis describes the scenario in which a horse is non-weight-bearing in one limb, perhaps due to an injury, and overloads the opposite limb for a prolonged period of time.

Excessive weight-bearing in the support limb leads to structural breakdown of the laminae and coffin bone rotation.

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Stages of Laminitis

With most cases of laminitis, there are generally three recognized stages:

1) Subclinical laminitis: microscopic changes occur within the hoof and the horse only shows minimal or subtle signs.

2) Acute laminitis: horse shows a sudden onset of lameness, with the degree of pain and severity of clinical signs ranging from mild to severe.

3) Chronic laminitis: occurs when a horse has had several episodes of laminitis or a prolonged course of pain following the initial episode, which have caused physical changes in the hooves, often including coffin bone rotation and/or sinking. Horses with chronic laminitis are at high risk for continued episodes.

Prevalence and Risk Factors

Unfortunately, laminitis is a highly prevalent condition affecting many horses worldwide. In a 1998 survey, 13% of US horse operations reported having a horse with laminitis. Of affected horses, nearly 5% had to be euthanized due to their diagnosis. [4]

Acute laminitis can occur in any horse that consumes a large amount of carbohydrates at once, such as when a horse gets into the grain bin or in experimental overloads of corn starch or fructan. In an owner-reported survey, over 50% of the cases were suspected to be due to grazing lush pasture or grain overload. [4]

Genetics is increasingly implicated in risk of metabolic syndrome and therefore also the risk of laminitis. [13] Pony breeds and some horse breeds such as Saddlebreds, Morgans, Tennessee Walking Horses, Paso Finos, and Arabians are at higher risk for developing metabolic conditions and endocrinopathic laminitis.

Horses of any breed may eventually develop hyperinsulinemia if they have PPID.

Early Warning Signs of Laminitis

Laminitis can be brewing and producing laminar damage before a horse becomes lame. Because of this, there are subtle warning signs that show up before major problems occur.

Being vigilant for these signs and taking immediate measures might mean the difference between a mild case of laminitis and one that becomes completely debilitating.

Many early signs of laminitis first appear as subtle changes in the hooves. Regular farrier care is one of the best ways to monitor and protect the health of your horse.

Some of the most common early warning signs of laminitis in horses include:

1) Hoof Wall Distortion

When the hoof laminae is healthy and the attachment between the coffin bone and hoof is strong, the foot will maintain a compact form, without distortion. When weakening of the laminar connections occurs, the laminae become stretched, proliferate, and lose strength.

Changes in the hoof wall, such as toes that grow long quickly or toes that have a dished or flared appearance, could signify that your horse has subclinical laminitis.

2) Hoof Rings

Hoof rings show up as a deviation around the hoof wall from the coronary band.

Various stressors can cause hoof rings to form. These include a change in diet, seasonal fluctuations in grass quality major life events such as foaling, or environmental changes. Laminitis is also a common cause of hoof rings, even in the early stages of the disease.

Hoof rings caused by laminitis appear slightly different from hoof rings caused by other factors. Instead of being evenly spaced around the hoof wall, rings due to laminitis or rotation are closer together at the toe than the heel.

If your horse shows signs of hoof rings, it may signify a window of opportunity for therapeutic intervention before the condition worsens. [5]

3) Loss of Sole Concavity

Some horses are more flat-footed than others, but if your horse has become more flat-footed than normal, this could be another indicator of subclinical laminitis.

Loss of sole concavity is more common in the front feet and occurs most commonly when the coffin bone drops or begins to rotate within the hoof capsule. Horses with a loss of sole concavity may be more prone to bruising.

4) Stretched White Line

The white line (a misnomer because it isn’t actually white) appears around the inner edge of the hoof wall as seen from the bottom of the hoof.

With laminar inflammation, this line can become stretched, forming a small gap around the edge of the sole. This gap may collect dirt, small rocks, or even rotting material.

Researchers say that a stretched white line is often the earliest noticeable change in horses with metabolic conditions such as insulin resistance. [5] A stretched white line indicates the beginning of laminar failure, but the good news is that it can be reversed in many instances.

5) Seedy Toe or Fungal Infection

Fungal infection often goes hand in hand with a stretched white line. White line disease is a fungal or bacterial infection of the hoof that can be caused by mechanical problems such as overgrown toes.

Fungal and bacterial infections can also be a telltale sign of subclinical laminitis.

Severe cases of white line disease can cause laminitis without there being any metabolic problem so a careful medical work up is needed.

Seedy toe is drying and crumbling of a stretched white line that does not necessarily involve an infection and does not extent up the hoof wall higher than the live sole plane level.

If you hear a hollow sound when tapping on the outside of the hoof wall above the level of the live sole, your horse likely has white line disease.

6) Chronic Abscessing

If your horse tends to get frequent hoof abscesses, this is another warning sign of an underlying condition such as laminitis.

Hoof abscesses can occur within the hoof wall, beneath the sole, or anywhere inside the hoof capsule. Abscesses often result in extreme lameness, which is only relieved when the abscess finds an exit tract (through the sole, heel bulb, or coronary band) and drains.

If you see changes in your horse’s hooves or if your horse tends to abscess every spring or multiple times throughout the year, a visit with your veterinarian is warranted.

7) Gait Abnormalities

If your horse develops a shortened stride or any kind of foot lameness, this may be an early indicator of laminitis.

When there is pain in the hooves, your horse’s gait will change as they attempt to relieve pressure. Horses with subclinical laminitis may show:

  • Stiff head carriage at the walk – high or low
  • Loss of the normal rhythmic sway to the back at the walk
  • Reluctance to trot on hard ground

8) Foot Lifting

When pain or pressure occurs in the hooves, horses may also lift their feet more than normal or frequently shift their weight. Horses may also refuse to lift a foot to avoid the pain of bearing weight on the opposite limb.

Too much foot lifting or a reluctance to lift the feet are subtle signs of laminitis.

9) Generalized Foot Soreness

Generalized foot soreness may show up as sensitivity to having the feet cleaned, a reluctance to move over hard ground, or a reluctance to walk downhill or even turn.

Soreness after shoeing or trimming has also been associated with higher rates of laminitis. [6]

10) Increased Digital Pulse

The digital pulse can be felt as blood flows through the arteries into a horse’s hoof. If there is inflammation of the tissues in the leg or hoof, or resistance to blood freely entering the hoof, pulse strength will be increased.

A pulse that is easy to find and bounding can be an early indicator of laminitis. [7]

When feeling for the digital pulse, use the index and middle fingers to feel on both the outside and inside of the leg just above the fetlock. Also, feel over the fetlock and down the pastern.

Do not use your thumb as you may end up feeling your own pulse instead of the horse’s. [7]

11) Increased Hoof Temperature

A warm hoof indicates inflammation occurring inside the hoof capsule. This can occur with an abscess or other types of hoof injuries, but it is also a common indicator of the beginning stages of laminitis.

Conversely, horses with septic/SIRS related laminitis often have ice cold feet from vascular constriction before the lameness and hot feet ensue.

12) Increased Insulin Levels

Horses with subtle signs of laminitis typically have underlying metabolic conditions which contribute to hoof changes in the first place.

Blood tests performed by your veterinarian may show increased insulin levels and your horse may be diagnosed with metabolic syndrome which includes hyperinsulinemia.

Insulin resistance is the failure of tissues to adequately respond to circulating insulin. [8] As tissues become less sensitive to the effects of insulin, more of this hormone is released causing levels to rise.

Dietary changes and exercise are needed to improve insulin sensitivity. This includes lowering the starch and sugar content of their diet by eliminating grains and transitioning to a forage-based diet.

13) Obesity

Obesity is common in horses with Equine Metabolic Syndrome and often is associated with early stages of laminitis.

Using the Henneke Body Condition Scoring system is the best way to evaluate your horse’s obesity status. A score of 7 or more indicates that your horse is carrying too much body fat and needs to lose weight. [8]

However, it is important to note that non-obese or even thin horses can experience metabolic problems and laminitis.

14) Regional Adiposity

Regional adiposity or fatty deposits that accumulate in certain areas such as along the top of the neck, on the rump, or behind the shoulder are a reliable indicator of metabolic disease.

If you notice regional adiposity, especially a cresty neck, your horse may also have sub-clinical laminitis. [9]

What to Do if Your Horse Shows Signs of Laminitis

Subclinical laminitis can occur over a prolonged period that can last for years. However, if you notice any of the above warning signs, it’s best to take action immediately.

Work with your veterinarian and a nutritionist to change your horse’s diet and address any underlying metabolic issues.

We recommend taking a hay sample and submitting it for analysis to get the most accurate information about your horse’s current diet.

Avoid concentrates with high NSC content (nonstructural carbohydrates; starches and sugars), or high-sugar treats. Additionally, your horse may need to be removed from pasture and fed low sugar (or soaked) hay instead.

Increased exercise will also benefit horses with metabolic disease and insulin resistance. Exercise promotes insulin sensitivity, encourages weight loss and increases blood flow to the feet.

However, you should only increase exercise if your horse isn’t lame or extremely foot sore. Working your horse on softer ground such as grass, sand, or in an arena is best.

Nutrition for Horses at Risk of Laminitis

Balanced nutrition is key to building out strong hooves and supporting your horse’s metabolic health.

To support hoof health, horses require adequate amounts of amino acids, trace minerals such as zinc and copper, and the B-vitamin biotin.

Many equine diets are lacking in these nutrients, which may cause problems for hoof health. Feeding a comprehensive vitamin and mineral supplement, such as Mad Barn’s AminoTrace+, will help to address common gaps in the diet and support hoof health.

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  • Complete mineral balance
  • Supports metabolic health
  • Formulated for IR/Cushing's
  • Hoof growth

AminoTrace+ is specifically formulated for horses at risk of laminitis and other metabolic issues. It is a low-HC formula that contains elevated levels of nutrients to support insulin sensitivity.

If your horse is displaying warning signs of laminitis, submit their information online for a free review by our equine nutritionists. Our nutritionists can help you design a feeding plan to prevent or recover from laminitis.

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References

  1. Patterson-Kane, J.C. et al. Paradigm shifts in understanding equine laminitis. The Vet. Journal. 2018. View Summary
  2. Frank, N. Endocrinopathic Laminitis, Obesity-Associated Laminitis, and Pasture-Associated Laminitis. AAEP Proceedings. 2008.
  3. Carbohydrate Overload. Fox Valley Equine Practice.
  4. USDA Lameness and laminitis in US Horses. USDA. 2000.
  5. Geor, R.J. and Harris, P.A. Laminitis. Equine Applied and Clinical Nutrition. 2013.
  6. Pollard, D. et al. Identification of modifiable factors associated with owner-reported equine laminitis in Britain using a web-based cohort study approach. BMC Vet Res. 2019. View Summary
  7. Equine Digital Pulses. Willamette Valley Equine Veterinary Services.
  8. Morgan, R. et al. Equine metabolic syndrome. Vet Rec. 2015. View Summary
  9. Fitzgerald, D.M., et al. The cresty neck score is an independent predictor of insulin dysregulation in ponies. PLoS One. 2019. View Summary
  10. Beythien, E. et al. Effects of sex, pregnancy and season on insulin secretion and carbohydrate metabolism in horses. Anim Reprod Sci. 2017. View Summary
  11. Guglick, M.A. et al. Mercury toxicosis caused by ingestion of a blistering compound in a horse. J Am Vet Med Assoc. 1995. View Summary
  12. Menzies-Gow, N.J. et al. Prospective cohort study evaluating risk factors for the development of pasture-associated laminitis in the United Kingdom. Equine Vet J. 2017. View Summary
  13. Stefaniuk-Szmukier, M. et al. Equine Metabolic Syndrome: A Complex Disease Influenced by Multifactorial Genetic Factors. Genes (Basel). 2023. View Summary