There are many, many different causes of laminitis and it is a common misconception that laminitis is caused by over-eating grass only. Although many cases of laminitis result from the ingestion of lush pasture, the disease can be caused by an animal gorging on excess carbohydrate such as grain.
It is not just the quantity of grass that is important in the development of laminitis; it is the type of grass and the sugars it contains. Nowadays, many horses and ponies are liveried on pasture which was once used for cattle. This type of grazing may have been heavily fertilised and re-sown with particular species of grass which are not suitable for horses and ponies.
Grass which is stressed by such things as an overnight frost or overgrazing will result in the formation of a type of sugar known as fructan. This sugar is the plant's form of storing energy in the form of carbohydrate and eating fructan can directly cause laminitis. The amount and the type of carbohydrate ingested are very important in the development of laminitis.
Laminitis can also result when an animal is sick for another reason. One example of this is when a mare fails to rid herself of the afterbirth (cleansing) after foaling. In these cases, mares can quickly develop an infection in the womb (known as metritis) and it is the toxins that are released from the metritis into the circulation which in turn lead to a cascade of events resulting in laminitis.
Occasionally, laminitis can develop in one limb where the opposite limb is painful for another reason. This is particularly a problem in heavy horses if they are affected by a foot abscess; the foot abscess causes the opposing limb to take more weight than it is accustomed to, resulting in laminitis.
Delays between foot trimming or shoeing are an important cause of stress and damage to the laminae. Regular visits by the farrier will also pick up the early warning signs of laminitis.
Horses vs. Ponies
Another popular misconception is that it is only ponies which develop the disease. This is not so and many horses are destroyed each year because of laminitis.
Equine Cushing's Disease (ECD)
ECD is a very common disease in equine animals from their mid-teens onwards, although it can be seen in animals as young as eight years old. Because of the hormonal changes in ECD, there is an increased risk of laminitis. The laminitis which develops secondary to ECD is very difficult to control unless the underlying disease is also treated and, unfortunately, the medicines used to treat ECD are expensive and not always effective. Owners with geriatric equines should be doubly careful about their animal's weight and liaise carefully with their vet or nutritionist to develop the best preventative strategy and grazing management.
Certain drugs, including those which belong to the group of medicines known as corticosteroids, can in some cases result in laminitis. Corticosteroids are commonly injected into joints to relieve inflammation, although they can be used for a wide variety of purposes. Veterinary surgeons are particularly careful about their use, although in most cases the benefit of treating the horse with cortisone outweighs the very small potential risk.
Please click here for advice on signs of laminitis, treatment and prevention.