Equine Laminitis, Explained

Horse owners are all too familiar with laminitis, a recurrent condition that affects 15% of U.S. horses and accounts for more than seven percent of equine deaths each year. This extremely painful and often debilitating disease is characterized by inflammation and subsequent damage of the laminae, or the connective tissue in the hoof. The laminae, often compared to velcro, support the entire weight of the horse by linking the hoof wall to the coffin bone of the foot. When this network of lamellar tissue becomes inflamed, the horse experiences tremendous pain and will become reluctant to walk or put weight on their damaged limb(s). If we are to prevent laminitis – or stop the progression of its symptoms – we must begin by exploring the complex nature of the condition. With this understanding, we can then piece together which causes – or combination of causes – triggered laminitis.

Although every laminitis episode involves unique complications, at the crux of all cases, blood flow to the laminae has been restricted. Improper blood flow results in nutrient and oxygen deficiencies, leading to localized inflammation, swelling, and pain. This initial attack of the laminae can founder a horse, or permanently damage the hoof and cause the death of the laminae.

Laminitis refers to the initial inflammatory attack on the tissue in the hoof, but it is also a systemic disease, meaning it affects the entire horse, rather than just one biological mechanism. This widespread attack on the body can make it particularly difficult to pin down the cause(s) of laminitis. To help differentiate between the systemic systems often involved in laminitis cases, most veterinary professionals group cases into three sets of causes:

1. Endocrine: Related to hormonal imbalances; accounting for about 90% of laminitis episodes. Excess carbohydrates, starch, grains, and sugars – as well as conditions such as Pituitary Pars Intermedia Dysfunction (PPID/Equine Cushing’s Disease), Insulin Resistance (IR) Equine Metabolic Syndrome (EMS) – can all cause endocrine related laminitis.
2. Supporting Limb: Injury to one limb, sometimes exasperated by obesity, will cause the equine to shift weight to the non-injured limb. This excess weight results in disruption of blood flow in the healthy, weight-bearing hoof.
3. Systemic Inflammatory: Sepsis (bacteria in the bloodstream) or disease can cause inflammation to develop throughout the body. Sepsis and infection such as Potomac Horse Fever, can all trigger this form of laminitis.

Even though about 90% of laminitis cases are diagnosed as endocrinopathies, laminitis is rarely a cut-and-dry hormonal issue; the other causes are often at work behind the scenes. This is in part due to the delicate nature of the laminae: these accordion-like tissues contain their own blood and nerve supply, making them particularly vulnerable to injury and inflammation. It is the perfect storm of hormonal, mechanical, and inflammatory issues that push a horse past “a threshold over which laminitis is triggered.”

Like with humans, food is often the cause of inflammatory issues and hormonal imbalances in horses. To date, starch, black walnut, oligofructose, fructose, and insulin have been experimentally proven to induce laminitis. In one study, it took only 48 hours of having 3-4 times the normal level of blood insulin for healthy horses to show the first signs of laminitis.

Evolutionarily, horses have digestive systems “designed to cope with a continuous supply of small amounts of roughage at a time.” This means that, if your horse grazes on large quantities of lush pasture – and doesn’t have much opportunity to exercise in the process – they are at risk of developing pasture-associated laminitis, also known as grass founder. Lush pastures are particularly dangerous in the spring and summer when grass has a higher sugar content. Grazing for just a half an hour on lush pasture can swiftly founder your horse. In fact, a UK survey found that 61% of laminitic animals were kept at pasture.

A lack of opportunity to exercise can also put your horse at risk of developing laminitis. As with humans, excess weight can irritate a horse’s biological systems. Obesity helps spur on laminitis by irritating the endocrine system, introducing toxins or bacteria into the bloodstream, or by putting more physical pressure on the horse’s hooves.

We must also be careful about overworking our horses on hard surfaces – this can lead to supporting limb laminitis. One of the most common results of overworking a horse is Road Founder, where the laminae and hoof wall separate. Anything that disrupts the blood flow to the laminae, such as excessive or improper hoof trimming, can make the laminae vulnerable to disease and infection.

Other Risk Factors

Laminitis affects all hoofed animals – including horses, ponies, cattle, donkeys, and mules. According to the Royal Veterinary College University of London, ponies are affected more frequently than horses, most likely due to genetically inherited insulin resistance. Other risk factors include:

• Time of the year (spring/summer grazing increases risk)
• Stress (from moving, etc.)
• Equines over the age of ten

Catching laminitis early requires careful observation, including physically checking horses for signs of pain. We must investigate our horse’s symptoms to discover the root causes. The first signs of laminitis include:

• Reluctance to walk, especially in circles or on hard surfaces (usually presents after the first 48 hours of a laminitis episode)
• Heat in hooves (increased digital pulse): if foot remains hot over 48 hours, this may be a warning sign
• Pain in toe when pressure is applied
• Changes to stride: is your horse carrying their weight abnormally or unevenly?
• Quality of coat: long, wavy coat may indicate a hormonal issue
• Fat distribution: excess fat in the neck area or  “cresty” neck – may indicate hormonal issues or a magnesium deficiency
• Weight change

As laminitis progresses, the horse may develop a laminitic stance in order to minimize pressure on their painful hooves. As laminitis commonly develops in front hooves first, a laminitic horse often starts to lean back on their heels and push their front feet forward to get relief – called a “sawhorse” stance. The horse will develop short, quick steps, and become slow-moving, shifting weight from one foot to the other. As the condition progresses, the actual structure of the hooves begins to change, making signs of damage more obvious. Other symptoms that indicate a chronic case of laminitis include:

• Widening white line on the sole of the hoof (indicates weak connection between laminae and coffin bone
• Laminitic rings: rings in the hoof wall get wider as you get closer to the heel (remember, laminitic rings are not the same as hoof rings!)
• Bruised soles of feet
• “Seedy toe” (a bacterial infection)
• Bulge in the sole of the hoof, caused by rotation of the pedal bone
• Narrow, slipper-shaped hooves (“Aladdin Slippers”), where heel grows faster than toe
• Solar prolapse, where the pedal bone penetrates the sole of the hoof

All advanced cases of laminitis involve a great deal of neuropathic pain – chronic pain usually associated with tissue damage. When pain becomes chronic, it affects the very neurotransmitters responsible for telling the brain that there is pain present. Thus, a vicious cycle ensues, making it increasingly difficult to stop the triggering of pain signals to the brain.

As hormone-associated laminitis is the most common, it is vital to check your horse for signs of preexisting hormonal conditions. These conditions can easily put a horse over the laminitis threshold. Signs of Cushing’s Disease and/or insulin resistance include: excessive thirst and appetite, a curly coat, excess sweating, and weight loss.

In addition to frequent vet visits to make sure you are properly monitoring your horse’s health, the following preventative measures will help you keep your horse in tip-top shape:

If you suspect your horse is suffering from laminitis, call your veterinarian immediately. After performing a thorough physical examination they will test the blood and check for underlying hormonal issues or sepsis. Additionally, if your vet suspects that your horse has laminitis, they will take radiographic images (x-rays) to determine if “phalangeal displacement” has occurred – including the extent of rotation and displacement of the coffin bone.

Once your horse’s lifestyle is in check and triggers have been removed, it is time to move forward with treatment options for horses already suffering from laminitis. Dietary management works in the very early stages, but laminitis is often caught too late for dietary changes to be enough to reverse the condition. If your horse has laminitis, your veterinarian may recommend one – or a combination of – the following treatment options.

Your veterinarian may recommend that you use a hoof boot, pads on the sole of the hooves, or temporary shoes. There are many types of shoes for laminitic horses, but the right shoe will depend on the types of structural changes that have occurred in your horse’s hooves, including how much the pedal bone has rotated within the hoof capsule.

To reduce the pain and increase blood flow to the hooves, your vet may prescribe Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) such as phenylbutazone. For acute cases of laminitis, vasodilators are often used in order to increase blood flow to the hooves. However, once the actual structure of the hoof begins to change (Founder), medication can only do so much. If symptoms reach this extreme, your veterinarian may recommend emergency surgery.

Molly, an Icelandic pony, had great success using the Loop to help treat endocrine-related laminitis (induced by Equine Metabolic Syndrome). After improving her nutrition and exercise routine, the Loop was used for 15 minutes two times per day. After 30 days, there was already a noticeable improvement. After six months of treatment, Molly had no lameness, no digital pulses, and the rotation in her hooves was steadily decreasing. You can read more about Molly’s story here.

For acute cases, natural solutions can be beneficial – as long as you are also working with your veterinarian to ensure that all other necessary measures have been taken. If your horse has a “cresty” neck, your vet will check for a magnesium deficiency; low levels of magnesium directly relate to insulin and glucose irregularities. If this is the case, magnesium supplements may help increase your horse’s sensitivity to insulin.

Many supplements may help if your horse has any nutritional deficiency; proper nutrition will help improve the structure of your horse’s hooves. Introducing more antioxidants may also help prevent free-radicals from causing tissue damage. If your veterinarian suspects that your horse has a hormonal imbalance, they may also recommend using supplements that contain levothyroxine sodium, which helps manage hypothyroidism.

If your horse is showing signs of extreme pain and they have not responded to less invasive treatments, their best hope is often surgery. The specific surgical techniques will depend on the type and extent of damage to your horse’s hooves. If your horse’s coffin bone has rotated, your veterinary surgeon may recommend a procedure called a deep digital flexor tenotomy. Other techniques such as a partial hoof wall resection may be recommended.

Whether your horse is recovering from laminitis or you are hoping to prevent a potential episode, there are many resources and tools at your disposal! With the help of your trusted veterinarian and farrier, feel confident that you can implement measures today which will improve the health and overall wellbeing of your beloved horse, for years to come.

DISCLAIMER: Assisi Animal Health does not intend to provide medical advice and this article is not written by a medical professional. The information provided in this piece is for educational purposes only. Consult your veterinarian before deciding on a treatment plan.