The old adage "No foot, no horse" is no truer than when it comes to laminitis. Any lameness in the horse is bad enough, but laminitis can be a devastating disease to your horse. When a horse suffers from a severe attack of laminitis, his feet and his condition can become an intense management situation for the rest of his life. To help understand this complex disease, one needs to know the anatomy of the hoof and foot, some causes of laminitis, signs of the disease and some treatment regimens.
Looking at the foot from the outside to the inside, it is made up of three major parts: the hoof wall, soft tissue connections and the coffin bone. All of these components together provide the surface, which the horse bears all his weight on, and provides the basis for movement. The hoof wall is the hard outer portion that we all can see and that your farrier nips and rasps down every 6-10 weeks depending on your horses' hoof growth and needs. The hoof wall grows down from the coronary band and stays attached to the bone by way of the soft tissue in between, known as the lamina. What we call the white line on the ground surface of the foot is actually the old lamina after it has grown out past where it needs to be attached to the bone.
Looking more closely at the lamina, there are long vertical columns of finger-like projections stretching down the entire hoof wall with similar columns attached to the coffin bone. These finger-like projections come together by interdigitating much like Velcro tabs do. When a horse goes through a bout of laminitis, the lamina in the feet, (primarily and most often the front feet) swell and become inflamed and the blood flow to the lamina is shunted around it. The swelling in this small area causes considerable pain to the horse and the lack of blood flow can lead to death of the lamina themselves, which can further cause detachment of the lamina from the hoof wall.
There are many causes of laminitis. The most common type is carbohydrate overload. This can be as straightforward as a horse getting into the grain bin and over consuming grain to eating lush grass pastures. Another cause is from some sort of endotoxemeia (toxins in the body), and/or systemic bacterial infection. Some examples are: colitis, small intestine obstructions or strangulations, retained placentas, and endometritis. Another cause is bearing weight exclusively on one side or foot because of severe lameness or fracture repair on another limb. Yet another cause of laminitis is caused by management problems. Some examples are: drinking cold water by an overheated horse, concussion or road laminitis, overweight horses, trimming too short, and bedding in Black Walnut shavings. Some miscellaneous causes include treatment with steroids, hypothyroidism, Cushing's disease, some toxic plants, mares being in continuous heat, and allergic type reactions to certain medications. Although we know that these different things cause laminitis in the horse, not all of the mechanisms by which these events cause laminitis have been discovered. What we do know is that the horse is in severe pain, some degree of vasoconstriction and vascular shunting occurs in the foot and if not treated promptly a varying degree of lamina death occurs which may ultimately end with permanent damage to the foot or feet.
Here is what to look for. Any signs of lameness after any of the above causes have been encountered. The horse will look as if he is walking on eggshells, when standing still will lift his feet repeatedly, and be very reluctant to walk on gravel or hard surfaces. In severe cases, the horse will also lay down a lot to relieve the pain from standing. In any case, if there is any suspicion of laminitis occurring or about to occur, get immediate veterinary assistance. We classify laminitis into four different categories. Acute laminitis should be classified as a medical emergency. Severe lameness is usually present and can develop rapidly. Potential for damage is great and intense therapy needs to be instituted immediately. The sub acute form is a milder degree of lameness and is usually caused by one of the management problems listed earlier. This type usually resolves quickly with appropriate treatment and with little or no permanent damage to the lamina. Refractory laminitis is when an acute laminitis does not respond to aggressive medical treatment in a week to ten days. This indicates the possibility of extensive laminar degeneration and continued inflammation. This can result in rotation of the coffin bone and penetration of the tip through the sole or complete detachment of the coffin bone from the hoof wall and "sinking" of the bone. Chronic laminitis is when there has been some previous rotation or "sinking" of the coffin bone and there is no active death or inflammation of the lamina. The horse then has a long toe and overgrows his heels. These horses suffer from more hoof abscesses and usually have recurrent acute lamanitic attacks.
In the acute stages of laminitis, there are as many treatments as there are predisposing factors. Our first goal is to relieve pain, eliminate inflammation and restore the proper blood circulation. To do this we start with nonsteroidal anti-inflammatory drugs (NSAID) like phenylbutazone, Banamine, ketoprophen, and/or DMSO, and padding to protect the feet with either foam pads or sand stalls. To increase the blood flow to the foot we use vasodilator drugs, like acepromazine, isoxuprine, and nitroglycerin. The next thing to do is to relieve the illness that is causing the laminitis or remove the causative factor. This treatment can be quite extensive as in intravenous fluid therapy, antibiotics, mineral oil through a nasogastric tube, or as simple as removing the shavings or by removing the horse from the pasture. An example of pre-treating a possible laminitis case is in grain overload. We will start with mineral oil through a nasogastric tube, a NSAID, maybe a vasodilator and if there was enough grain eaten or an overweight horse, and we will pad his feet.
The chronic lamanitic cases take more management care than the usual aggressive medical care. This entails therapeutic shoeing with radiographic diagnostics for correction of hoof-bone abnormalities and for the prevention of solar abscesses, proper diet if obese and maintenance of body condition if the horse is down.
Laminitis can be a very destructive disease. It can cripple a horse and create a huge financial burden for the owner. In the end, a horse with laminitis may have a grave prognosis and depending on the cause and duration may only be pasture sound. If you think your horse may be suffering from a bout of laminitis call your veterinarian immediately, because as the disease progresses and the foot anatomy changes, these changes are irreversible.