Laminitis and its Prevention
Friday, 30. October 2009
Laminitis is a serious hoof disease and the second most common cause (after colic) of premature death among domestic horses. Although laminitis is seldom fatal in itself, serious cases often lead to euthanasia either for humane reasons (the horse is crippled and in pain) or because the hoof damage means the horse can no longer be used.
The horse hoof contains connective tissue which holds the hoof bone (the pedal bone) in place and connected to the hoof wall. This tissue is known as laminae and if it becomes damaged the result is known as ‘laminitis’. Minor damage results in inflammation of the tissue and temporary pain. More severe cases reduce the strength of the connective tissue, allowing the pedal bone to rotate and sink within the hoof. In the most extreme cases, the pedal bone will actually penetrate the sole of the hoof and be visible. In mild cases the horse can return to normal duties but in more severe cases (depending on the amount of rotation and sinking of the pedal bone) the horse will have to be retired, with the worst cases requiring that the horse is immediately put down. Although there are a number of treatments for laminitis, once the damage is done they can provide only minor improvements, so the emphasis needs to be on prevention rather than treatment.
The term ‘founder’ is associated with laminitis but can be used in several different senses. Some people use founder as the lay term for laminitis, while others use it to describe the more serious forms of laminitis (e.g. when the pedal bone penetrates the sole).
There are two main sources of damage to the laminae, leading to laminitis. One is toxins, which enter the blood and travel to the laminae, where they cause inflammation and tissue breakdown. The other is mechanical, where the laminae is damaged due to repeated shocks to the hoof (e.g. from running or jumping on hard surfaces).
Overly rich food changes the bacterial population in the intestines, with a subsequent release of toxins by the bacteria. It occurs when the horse received a large amount of food which is too high in carbohydrates or nitrogen. This can occur either with rich feed (e.g. grain or muesli) or lush pasture. Pasture is most likely to be too rich in spring, when rain follows a dry period, or when fertilizer has been used. As some breeds (especially ponies) are more sensitive, special care should be taken that neither their feed nor their pasture is too rich. When putting horses and ponies on rich pasture, one should limit the amount of grazing time and consider the use of a grazing muzzle to restrict the amount they eat.
Competition horses, such as jumping or racing horses, which are frequently worked on hard ground, are relatively likely to eventually develop laminitis. However, it can also occur in pleasure horses, if they work or travel on hard surfaces. Try to avoid use of your horse on hard ground. If it is necessary to travel on hard surfaces, try reducing the pace since a walking horse will have less hoof shock than a running horse. Ensuring that hoof trimming is correctly done, especially avoid trimming for long toes or over-trimming as these reduce the ability of the hooves to absorb shocks. If the horse is shoed, it should be done by a competent professional. Consider using shock-absorbing shoes (e.g. horse shoes with a rubber component) or shock absorbing boots during competitions (both are increasingly being used, even at the professional level).
The third major cause of laminitis is toxins which are unrelated to overly rich feed. This includes toxins which are ingested (e.g. through moldy hay, or grass which has been treated with herbicides) or toxins which are produced due to an infection within the horse. Ensure that food does not contain fungus, mold or chemicals. Ensure that any infections are promptly and aggressively treated, before they can result in toxin overload leading to laminitis.
This Laminitis and Founder article is part of the Horse Care series by Dr. Doug Stewart