What is Laminitis and Founder?

Laminitis is an inflammation (swelling) of the sensitive laminae of the horse’s foot. The sensitive laminae are normally bonded or interlocked with the horny laminae of the hoof to support the horse’s weight on the hoof wall. Founder is a nautical term meaning sink. The coffin bone rotates or sinks inside the hoof capsule when the hoof bone bond fails. Founder is a sequela (result) of severe laminitis.

The swelling or edema of laminitis is caused by a leaking of serum from the foot blood vessels. The edema is trapped between the hoof wall and bone compressing the vessels and nerves creating intense pain. Eventually the reduced blood flow caused by the edema or by the shunting of blood by arteriovenous anastamoses (valves between arteries and veins) causes the laminar tissues to die. The hoof bone bond then fails and the bone rotates or sinks within the hoof capsule due to interstitial (between cells) fluid pressure and the weight of the horse. The blood supply of the sole is compromised by the sinking bone causing a dropped sole. The bone may even penetrate the sole. In addition, the entire system of the horse is affected.

Healthy horse hoof structure

Pastern bones (P1, P2 and P3) aligned with P3 parallel with the hoof wall.
© 2020 JoAnne Rissanen

Foundered horse hoof structure

P3 has rotated down due to separation from the sensitive laminae. Painful inflammation of the laminae causes lameness.
© 2020 JoAnne Rissanen

How Can the Horse Owner Tell If a Horse is Foundered?

Laminitic and foundered horses have a typical stance where they rock back on their hind legs and extend their front legs in an effort to shift the weight off the painful toes of the front feet. The sinking of the bone may be detected by running the thumb down the front of the pastern to see if your finger will sink in at the coronary band or slide off easily.

The acute form of laminitis can be life threatening. The horse will go off its feed, have an increased body temperature or fever, increased pulse and respiration rates, and a stronger than normal pulse in the digital artery. The affected feet may be warm to the touch. The horse may lie down frequently, be reluctant to get up, and have difficulty walking – especially the first few steps. Due to intense pain, horses may suffer from muscle spasms, experience profuse sweating and lose weight. A veterinarian should be called if any of these signs are present to prevent further tissue damage.

The chronic form is the result of an acute case that has recovered but the foot is damaged and has not fully healed. It can be a nuisance that keeps a horse from being sound. Chronic foundered horses generally have a hoof toe that is dish shaped and rings that are wider at the heel than at the toe. They require regular farrier maintenance and especially strict attention to diet and avoidance of stress.  How horses handle stress varies with each horse.

What Causes Founder?

Animals that are overweight or kept in “show shape” are at greatest risk for founder. One of the precursors to laminitis is equine metabolic syndrome. This is a hormonal condition brought on by stress due to diet – excess carbohydrates or sugars from grain or grass, lack of a companion, feed toxins, hormone imbalance, high fever, irritating noise, severe weather change, travel by trailer, plane or ship, infections in the intestines or uterus, and excessive ground concussion. Soaking feet in cold water may help prevent vessel leakage and edema.

All stressful conditions cause the adrenal glands of the horse to release cortisol. Cortisol causes a thinning of the blood vessels. This eventually causes them to leak fluid into the interstitial space between the vessels. The extra fluid compresses the blood vessels preventing blood from flowing through them. Without the oxygen and nutrients supplied by the blood, the tissues die. The fluid pressure and the horse’s weight cause the hoof bone bond to come apart and the bone to rotate or sink. Necrotic (dead) tissues frequently abscess.

What Can the Veterinarian Do?

Acute laminitis is very frustrating. Putting the suffering animal to sleep (called euthanasia) may appear to be the most humane and practical thing to do. Usually the vet will administer a purgative (laxative) such as mineral oil, to evacuate the bowel and prevent absorption of toxins. In most cases a pain killer is prescribed. These drugs should not be used for an extended period as they may cause the horse to further damage the laminae by excessive weight bearing, since the foot no longer hurts. Blood tests are done to determine if an infection is present. Radiographs (X-rays) are necessary to determine the amount of bone displacement and the condition of the bone tip. The more bone displacement and erosion of the bone tip – the less the chance of a full recovery. In conjunction with the farrier, a veterinarian may perform a toe resection to relieve pain and drain abscesses.

What Can the Farrier Do?

A qualified farrier who is experienced with this serious disease should be used – one who works well with a veterinarian. The farrier will trim the hoof to restore foot balance and prepare it for a special shoe. The fullered heart bar shoe gives the greatest chance for success. This shoe temporarily transfers weight from the painful hoof wall to the frog. There should be no sole pressure. A hospital plate may be necessary if the bone perforates the sole. Plates must be cleaned under and remedicated daily.

The heart bar shoe must be reset monthly as the hoof grows out to compensate for normal hoof growth which takes the frog away from the frog support. There are many fad type shoes recommended by inexperienced farriers and veterinarians. Experience shows that they are not as effective as well made and fit heart bar shoes. After several months, perhaps as long as a year, the heart bar shoe can be discarded and regular work resumed. Some horses with weak laminar attachments may require a heart bar for the rest of their lives. The heart bar is a pain reliever, and pain medication is not necessary while using them and may be detrimental to healing.

Heart bar Shoe

The farrier uses a heart bar shoe to shift weight bearing to the heel and frog and away from the toe. This reduces pain and allows the hoof to heal.
© 2020 Jim Blurton

What Can the Horse Owner Do?

Once a horse has been diagnosed and treated by a veterinarian and farrier, if will require daily care for a while – even several months. A deep bed (12 inches of wood shavings or wheat straw) will encourage the horse to lie down and keep its feet at the same level as its heart. Exercise should be limited at first. Later movement can be encouraged by putting the horse in a dry lot with others.

Hooves will need to be trimmed and therapeutic shoes reset monthly. Feet must be cleaned out daily to prevent sole pressure. The stable must be kept dry and clean. The exposed portion of the hoof resection will need to be treated with sugardine to draw out abscesses. (Sugardine is a mixture of table sugar and 3% iodine, commonly called povidone iodine, mixed to the consistency of a paste). This will dry up abscesses and keep them from forming. Soaking the feet in an Epsom salt solution will also cause abscesses to break and drain. A drawing agent such as Icthammol 20% or an Epsom salts poultice paste can also be used on abscesses between soakings.

Foundered horses should be fed grass hay and supplemented with Farrier’s Formula® to help repair damaged tissues. Fat horses should be fed a restricted feed intake. The horse’s condition should be no greater than a six on the condition scale – you can’t see the ribs but you can easily feel them.

What is the Prognosis (Outcome)?

The prognosis or outcome depends on many factors that affect the tissue damage in the foot and the rest of the body. This may be difficult to determine immediately. Mild cases of laminitis may recover in 30 to 60 days. However, this is rarely the case. Horses severely affected may never gain complete soundness and spend the rest of their lives in pain.

Horses that are treated conscientiously and regularly have a chance of completely recovering. Yet, it may take several months or even a year for a severely affected horse to show improvement. A horse with a large healthy frog, a strong will to survive, the ability to tolerate pain, and that receives regular care, has the best chance of recovery. Attention to routine nursing care by the owner is usually the most significant factor in influencing an afflicted animal’s recovery rate. Rates vary according to individual case severity and quality of care.

Making the decision to put a suffering horse down versus spending the financial and emotional resources necessary to nurse one through the course of the disease can be difficult.

Recommendations

Analyze the case carefully before making a commitment. Examine the options. Request radiographs. Use a fullered shoe to coincide with the perimeter of the coffin bone. (Fullering allows nail removal without trauma to the sole). Use a hospital plate if the sole is sensitive or if the bone is exposed. Reset the shoe every 30 days to reestablish balance and frog contact until it is not needed. Patiently explain the daily care required by the owner – remove dirt from the sole daily, dress infected areas, provide a deep stall bed, and feed a limited diet low in carbohydrates. Don’t give up easily – each horse heals at a different rate. There will be ups and downs. Prevent a reoccurrence by proper diet and environmental management.