Founder in Horses: Symptoms, Causes, and Treatments

If you’re familiar with equine laminitis, you may have also heard the condition referred to as founder. Some equine professionals, veterinarians, and caretakers may use the term “founder” to broadly describe the different phases of laminitis, while others define founder as a specific and severe pathology that sometimes occurs in the hoof after the onset of laminitis. Laminitis describes acute or chronic inflammation of the interlocking tissue (laminae) in the equine foot that binds the hoof wall to the coffin bone. This inflammation damages the laminae, weakening the bond between the hoof wall and the underlying coffin bone.

In this guide, we’ll use the latter, more specific definition of founder to break down how laminitis can progress into this severe and crippling condition. We’ll also describe the symptoms and causes of founder in horses and what treatment options are available.

Read on to learn more.

What is Founder?

Working within a narrow definition that some veterinarian institutions and researchers use, founder occurs when laminitis of the hoof progresses to the point that the laminae binding the hoof wall and the coffin bone together break down and detach from inflammation, resulting in the rotation and downward displacement of the coffin bone within the hoof capsule. For founder to occur, laminitis must first progress from subclinical to acute and finally to a severe stage of chronic laminitis. Horses can have laminitis without foundering, but they must first develop laminitis to become affected by founder. Once the horse founders, the rotation of the coffin bone is irreversible. However, treatments exist to help the horse regain strength and mobility and to reduce pain in the affected foot or feet.

Once laminitis reaches a severe, chronic stage of damaging inflammation of the laminae, the risk of founder is present. While all stages of laminitis can be painful for the horse, once the condition progresses into founder, the horse typically experiences severe pain and lameness. This is due to the rotation and sinking of the coffin bone into the sole of the foot. Often, barring instances of injury, both front feet are affected.

Founder in Horses: Signs and Symptoms

Since founder results in the detachment of the coffin bone within the hoof capsule from the hoof wall, pain is typically severe. The following signs and symptoms will likely be present if your horse is suffering from founder:

• Extreme reluctance or inability to walk.
•  Marked gait change.
•  Shifting of weight off the front feet onto the back legs in an exaggerated stance (laminitic stance).
•  Lethargy or depression.
•  Increased digital pulse in affected feet.
•  Heat in the hooves.
•  Bulge in the hoof sole from displaced coffin bone (solar prolapse).
•  Long, dished hoof toe and low heel.
•  White laminitis rings on the hoof.
•  Acute pain response when handling soles of affected feet.
•  Radiographic changes of the coffin bone and obvious laminae breakdown.

Founder in Horses: Causes and Treatments

Since horses must develop laminitis before the condition progresses into founder, the causes for both conditions are the same. Veterinarians typically separate these causes into the following three categories:

• Endocrine disorders that feature insulin dysregulation (endocrinopathic laminitis).
•  Injury-derived (supporting limb laminitis, or SLL)
•  Toxicity (sepsis-associated laminitis)

Endocrinopathic-Associated Founder

Some horses are environmentally or genetically at risk of developing laminitis, which may progress to founder. These horses most commonly suffer from either equine metabolic syndrome (EMS) or pituitary pars intermedia dysfunction (PPID, formerly known as equine Cushing’s disease). Senior horses and ponies are statistically more at risk for having EMS and PPID. Equine caretakers will need to work with their vet on a long-term dietary, environmental, and medicinal management plan to reduce the chances of endocrinopathic laminitis developing into founder.

Injury-Associated Founder

If a horse suffers an injury to its foot, it may develop supporting limb laminitis (SLL). This typically occurs for long-term injuries in which a horse is highly reluctant or unable to bear weight on the injured foot. As a result, the horse puts excessive weight on the opposite foot during rest, causing inflammation in the laminae. In cases of injuries that last several weeks, the SLL may progress into founder. To prevent foundering via compensatory weight-bearing, caretakers will need to actively work with their vet on reducing inflammation to the supporting limb, encouraging bouts of weight-bearing on the injured limb when possible, and stalling or paddocking the horse on soft ground or mats.

Toxicity-Associated Founder

One of the most common causes of an acute bout of laminitis is a toxicity-associated event. This can occur when an at-risk horse consumes an overload of grain or sugary grass. Acute bouts of laminitis are particularly common in the spring when at-risk horses reintegrate lush grass into their diet. As a result, acidosis of the hindgut occurs, causing a mass die-off of beneficial fiber-digesting bacteria, which release a concentration of toxins. This sudden release of toxins in the hindgut causes a cascade of pro-inflammatory responses that can quickly lead to inflammation of the laminae, resulting in acute laminitis lasting less than three days. In this event, your horse may recover without developing recurrent or chronic laminitis. Dietary management is typically needed to prevent further acute occurrences.

If acute bouts of laminitis continue to occur or last more than three days, the condition will develop into chronic laminitis. This doesn’t mean the horse will absolutely suffer from founder, but once they hit the chronic stage, the laminae become consistently damaged and weakened. It’s crucial to properly manage chronic laminitis to reduce the chances of foundering. In cases of acidosis caused by sugar overload, long-term dietary and environmental management is critical.

Founder in Horses: Risk Factors

Some horses are more at risk of developing laminitis that can progress into founder due to genetics, environmental factors, age, weight, stress, and activity levels.

As mentioned above, endocrinopathic conditions can increase the risk of a horse developing chronic laminitis, which can progress into founder. Obese horses are also more at risk, and obesity can result from metabolic illnesses characterized by insulin dysregulation. Senior equines are more at risk of developing founder due to PPID. Currently, PPID affects over 20% of senior horses, ponies, and donkeys. EMS is also linked primarily to senior and obese equines. Caretakers often characterize these horses as “easy keepers” because they quickly put on weight and often don’t require grain in their diet. However, “easy keepers” are more at risk of developing toxicity-associated laminitis that can progress into foundering via hindgut acidosis.

Additionally, chronically stressed horses may be at an increased risk of developing laminitis. While there isn’t a clear consensus on the effects of stress on equine health, several studies have found correlations between increased stress levels and common equine GI disorders and laminitis. The theory is that in some individuals, chronic distress may lead to widespread inflammatory responses in the body, triggering conditions such as laminitis, which may progress into founder. A multitude of environmental factors can create chronic stress for horses, such as extended stalling, aversive training, poor pasture management, and lack of access to consistent foraging, freedom of movement, or equine companionship.

Finally, the frequency and intensity of exercise your horse engages in can create risks for founder. While consistent, light to moderate exercise can reduce the effects of insulin dysregulation-causing laminitis, excessive exercise, especially on uneven or hard ground, can increase the risk of trauma-induced laminitis. Repeated bouts of trauma-induced laminitis increase the risk of developing founder.

The photo featured at the top of this post is © Sebastian Frank/iStock via Getty Images