Laminitis (founder) is a painful condition characterized by inflammation of the blood vessel-filled laminae holding the coffin bone to the inside of the hoof. The term laminitis is a technical term used to describe the sudden onset of laminar inflammation, while the term “founder” is a lay term applied to the same condition. All Laminitis cases are not created equal. Depending on the cause of the inflammation, it may present sudden and severe, or slow, mild, and insidious. This later type will sneak up on you. The more severe the laminitis is at its onset, the greater the chance for chronic problems and recurrence, but a chronic case of undiagnosed “low-grade” laminitis can has permanent, crippling effects as well. This condition is not usually seen in foals under 6 months of age.
When it comes to laminitis, there are 2 general forces that influence the position of the coffin bone within the hoof: the downward push of the horse’s weight and the upward pull of the deep flexor tendon as it attaches to the sole surface of the coffin bone. In horses with laminitis, when the downward force is greater than the upward pull of the flexor tendon, the coffin bone “sinks” in the hoof capsule. More commonly, however, inflammation around the coffin bone helps to push the toe down while the deep flexor tendon pulls the toe down and backward, causing coffin bone “rotation.” At the same time, inflammation of the laminae causing swelling, increasing the pressure within the rigid hoof. This increased pressure damages the blood vessels of the laminae. These changes are usually permanent. Therapy is generally focused on reducing inflammation, alleviating pain and returning the foot to as normal a position as possible (this is often achieved in conjunction with your farrier).
Causes of Laminitis
Laminitis can occur with no “apparent” reason, but often there is some underlying cause. The underlying condition can often be cured, but the laminitis may persist, leaving the horse with chronic (long-term) founder. If not a cause for euthanasia, chronic founder requires special attention for the rest of the horse’s life.
The following factors contribute to the onset of laminitis:
Imbalance of exercise to food intake: This is a simple calorie output to calorie input. Obesity is one of the leading causes of founder that we see on a regular basis. A cresty-necked pony or horse with a genetic propensity for being overweight, that eats too much spring pasture, or that eats too much grain is at a high risk of developing this disease.
Percussion/stress founder: A fit (lean) athletic horse that is worked harder than usual on a hard surface can develop “road founder.” This occurs with repeated percussive forces to the sole of the hoof. Like a horse trotting on asphalt.
Endotoxemia from illness. Certain bacteria can produce endotoxins, which damage the laminar blood vessels. Endotoxins can be produced in such diseases as severe colic, uterine infections, retained placenta, diarrhea and pneumonia, and with complications after foaling.
Cortisone release or steroid use: Stress causes the adrenal glands to release cortisol. This stress can be acute (high levels over a few days) or chronic (low levels over a prolonged duration). Stressful situations for your horse may include training, competition, and shipping. Any steroid-type of drug, such as hydrocortisone, dexamethasone or triamcinolone, should be used cautiously and only under veterinary direction and only when absolutely necessary. In treatment of certain immunologic or respiratory diseases, cortisone is potentially life saving, but the large doses necessary to alleviate those symptoms may cause laminitis.
Metabolic diseases: Horses with certain metabolic disorders like Cushings, Type II Diabetes (Insulin Resistance), Hypothyroidism or Polysaccharide Storage Myopathy (PSSM) usually develop laminitis from increased production of cortisone and high circulating glucose levels. These horse’s are also generally overweight despite a low quantity of food intake. If left undiagnosed, horse’s will continue to founder uncontrollably. Determining and correcting the ultimate underlying cause of the laminitis is critical to the life of the horse. In some cases, there is not only one but a combination of disorders that are causing the symptoms.
Conformation or genetic predisposition: Heavy horses or ponies are more likely to develop laminitis. Also, horses with thin or flat soles do not have as much protection of the coffin bone.
Clinical Signs of Laminitis
Heat in the feet.
Increased digital pulse.
Pain on application of hoof testers near the point of the frog.
Sinking or rotation of the coffin bone on radiographic examination.
Reluctance to walk (like on egg shells) or trot.
An abnormal stance (horses will rock back on their haunches and point their front feet out)
Laying down more than usual.
Important Points in Treatment
Radiographs (x-rays): Radiographic examination of the affected feet can evaluate the position of the coffin bone and determine the severity of the damage. Repeated radiographs can help determine if the founder is under control or if it is still occuring.
Medication: Anti-inflammatory therapy is critical to stopping the cycle of inflammation and damage. Adjunctive therapy also usually includes drugs that increase circulation to the feet. It is important to give these medications as prescribed. Though your horse may appear more comfortable after treatment has begun, it takes considerable time to reduce inflammation in the foot. Laminitis commonly recurs, especially if the horse is not medicated as directed. In severe cases, medical therapy could include intravenous fluid/DMSO therapy and long term pain management through a constant rate infusion of strong analgesics.
Foot protection: Keep your horse on a soft surface until this episode of laminitis is completely resolved. Increase the thickness of its regular bedding, and add sand to their paddock. Provide support for the frog, as with pads. When applying frog support, do not place tape on or over the coronet. This will decrease an already compromised blood supply to the foot. Check the position of the frog support several times daily to make sure it is in its proper position.
Diet: I cannot stress this enough. Do not overfeed and monitor your horse’s body weight to prevent excess weight gain.
Exercise: This is key is prevention. Your horse needs regular exercise to stay fit. After an episode laminitis has subsided, be careful not to overwork an out of shape horse as overworking can lead to a recurrence of laminitis.
Farriery: Your farrier is very important in this process, because they can help maintain the horse’s comfort level through proper trimming, shoeing, and support techniques. Shoeing is sometimes necessary and these decisions are generally formed on a case by case basis. Regular keg shoes applied in the traditional manner (not backwards) without pads or support packs are almost never recommended and cause more pain by applying additional pressure to the toe. Your veterinarian should consult with your farrier to discuss your horse’s therapy and shoeing. Often times the key to full recovery is a good working retionship between you, your vet and your farrier.
Prevention of Laminitis
The most important way to prevent laminitis is to avoid overfeeding certain feedstuffs (like grain) and hoof trauma:
- Bed stalls and exercise your horse on appropriate sole-supporting bedding/footing.
- Do not apply tape or constricting bandages around the coronary band.
- Do not force your horse to walk on gravel or rocky surfaces without adequate shoeing.
- Carefully monitor your horse’s intake of carbohydrates and body condition.
- Allow your horse to exercise each day.
- Have your horse correctly shod and avoid trimming the feet too closely.
- Have your veterinarian investigate problems like obesity in the absence of high calorie intake.