Laminitis

What is laminitis?
This is a common, severely debilitating, painful and potentially life threatening disease of the soft tissue within the hoof capsule, and occurs in ponies and horses of all ages, breeds, and uses.

What are the signs of laminitis?
There are many different ways in which the condition may present, depending on the susceptibility of the animal in question and the severity of the inciting cause. If mild – the signs may be as subtle as choosing to walk on the verge rather than the road when out riding, appearing “pottery” when turned on a hard surface, or walking over to the gate at feeding time as opposed to the usual charge! When more severe the animal will show obvious lameness in the effected feet. The fore feet are most commonly affected however it may occur in the hind feet, all four feet, or just one. Increased heat and a pounding digital pulse may be evident in the effected feet but this is not always obvious. A classic laminitic stance involves both hindlimbs tucked well under the body and the forelimbs stretched out in front. These horses are reluctant to move and when forced appear to be walking on eggshells. When very severe the horse may be sweating, shivering, inappettant or lying down.

What causes laminitis?
At this time we do not fully understand all the mechanisms involved with the development of laminitis, however the underlying problem is an alteration in the blood supply to the effected feet that results in damage to the sensitive tissues (laminae) that form the attachment between the pedal bone and the hoof wall. Once damaged the laminae will swell within a confined area, causing significant pain and some cell death. If enough cells are killed the lamina junction may fail resulting in movement of the pedal bone within the hoof capsule. This can produce rotation of the pedal bone or in extreme cases ‘founder’ (whereby the pedal bone sinks within the hoof capsule).

Most laminitic cases result from two relatively common endocrine diseases: Cushing’s Disease and Equine Metabolic Syndrome (EMS).

Both of these diseases result in higher than normal circulating insulin. It is these high levels of insulin circulating in the blood stream that precipitate laminitis.

In addition Cushingoid horses will have high circulating quantities of corticosteroids meaning an even greater risk of laminitis.

The vast majority of horses that sustain more than one attack of laminitis will have one or both of these diseases.

Other causes that result in laminitis include:

• Digestive upsets due to grain overload or abrupt changes in diet.
• Sudden access to excessive amounts of lush forage before the horse’s system has had time to adapt; this type of laminitis is known as “grass founder”.
• Toxin release within the horse’s system. Any illness that causes high fever or serious metabolic disturbances has the potential to cause laminitis, e.g. Severe colic, Retained placenta in the mare after foaling, pleuropneumonia.
• Excessive concussion to the feet, often referred to as “road founder”.
• Excessive weight bearing on one leg due to injury of another leg (fracture, joint infection) or any other alteration of the normal gait.
• Prolonged use of high doses of corticosteroids.

What factors increase the risk of laminitis?

• Heavy breeds, such as draft horses.
• Age – horse over 15 years old are at increased risk of developing Cushing’s Disease
• Obesity. Over weight horses are at an increased risk of developing EMS.
• High nutritional feeds (especially a high in starch content).
• Ponies.
• Unrestricted aces to lush pasture.
• Previous episodes of laminitis.

How is laminitis treated?
In many cases the condition is mild enough for box rest, anti inflammatories such as “bute”, restricted diet, and removal of any inciting cause may be sufficient. Frog supports, acepromazine ( a drug that reduces blood pressure) may also be used depending on the individual case. If there has been significant damage to the join between hoof capsule and pedal bone (as identified on X-rays) remedial foot rimming and shoeing will be required, and recovery may take several months. In cases where the pedal bone has penetrated the sole the prognosis is very poor and euthanasia required. There are a multitude of other treatments that have been put forward for the various forms of laminitis, and a range of opinion concerning what works best still exists amongst vets and farriers.

It is vital to treat any underlying disease such as Cushing’s or EMS otherwise treatment is likely to fail.

How do I prevent laminitis?

• Monitor you horse’s condition prevent obesity through control of diet and exercise. If your horse is overweight then testing for EMS is recommended.
• Testing for Cushing’s Disease in any horse over 15 years of age and certainly if they have a history of laminitis.
• Restrict grazing when the grass is lush (box rest, grazing muzzles or strip grazing using electric fencing may all be useful).
• If supplementary feed is required use high fibre low starch feeds (see nutrition advice) such as hay or haylage (avoid soft haylage), oat straw, high fibre cubes, unmolassed sugar beet (such as Speedibeet) and high fibre chaff. Conventional horse and pony nuts, coarse mixes and other starchy feeds or nuts should be avoided.
• If feeding concentrates avoid sudden increases.
• Avoid fast work on hard surfaces.
• Monitor for serious illness such as colic, diarrhoea, and uterine infection following retained placenta. In such cases veterinary help is required as soon as possible.