Laminitis – John Kohnke

Founder is one of the most crippling diseases of horses and ponies, which in severe and recurring cases, can reduce a horse’s usefulness and lifespan. Laminitis, the initiating cause of founder, can affect any horse, of any age or sex, at any time of year. Although it is traditionally considered a disease of fat ponies, laminitis can be triggered by a variety of metabolic or physical causes in any horse.

Laminitis is now considered to be caused by devitalistaion of the supporting laminae within the hoof, leading to painful breakdown and tearing of the support tissues suspending the pedal bone within the hoof. If laminitis is not treated properly, the pedal bones drops or rotates downwards, resulting in founder, with total collapse causing severe lameness and risk of death.

* The normal hoof structure
* Common causes for laminitis
* Symptoms of laminitis
* Diagnosis of laminitis
* First Aid
* Treatment of laminitis
* Prevention of laminitis
* Related Products

The normal hoof structure
The hoof consists of two main parts, an outer hoof shell or capsule of hard external wall and sole, which supports and protects the inner pedal bone and other structures.

The pedal bone is attached to and suspended within the outer capsule by 600 leaf-like folds or laminae of hoof wall material projecting inward from the hoof wall. These non-sensitive projections intermesh with outward projecting sensitive corium laminae attached to the outer surface of the pedal bone.

The hoof wall laminae are in turn covered with 100-150 pliable secondary laminae, which bond to similar projections on the sensitive corium laminae attached to the pedal bone. This whole zone of intermeshed supporting laminae forms the white line or white zone seen at the hoof wall-sole union. The laminae provide the structural support to attach the bony skeleton within the hard, outer hoof wall.

Common causes for laminitis
Laminitis can be triggered by a variety of metabolic and physical causes. Most commonly, the disease is the end result of a digestive upset caused by over indulgent feeding practices, particularly heavy grain or lush pasture intake.

When horses and ponies eat low grain hard feeds and graze pasture with a low content of carbohydrates (starches and sugars) these energy sources are digested in the small bowel. However, if horses gorge on grains, or consume a high grain meal (starches), or hungrily graze a large bulk of lush pasture (soluble sugars) the excess carbohydrates that are not digested pass on into the large bowel. Fermentative bacteria in the large bowel rapidly increase in numbers to attack the carbohydrate mass to break it down.

This fermentation produces abnormally high amounts of lactic acid (hindgut acidosis) which in turn kills off other bacteria and damages the gut wall, releasing endotoxins that are absorbed into the blood. It is these endotoxins that are thought to alter the blood circulation within the hooves, or cause the devitalisation of the basement cells on the surface of the lamina.

Certain individual horses and ponies are more sensitive to the carbohydrate in their diet, and only small increases appear to be necessary to trigger the onset of a painful laminitis episode. Grey ponies in particular seem to suffer a higher incidence of grass laminitis, and certain bloodlines are more sensitive to seasonal bouts of recurring founder. However, sudden unaccustomed intake of grain or lush spring pasture can result in laminitis in any horse or pony.

Laminitis can also develop secondary to a number of other diseases. These include toxic reactions from intestinal damage due to twists or blockages, infections such as pneumonia, diarrhoea, peritonitis or uterine infections in mares which retain their membranes after foaling.

Less common causes of laminitis include hoof concussion from fast work on hard surfaces, excessive weight bearing by one leg due to a severe injury or lameness in the opposite leg, stress from long distance transport, cancer of the pituitary gland, and administration of excessive doses of certain drugs, such as corticosteroids.

Symptoms of laminitis
The symptoms of laminitis vary according to the severity of the devitalisation of the laminae, internal changes within the hoof and the timescale of onset.

Acute Laminitis:
Most owners are familiar with the more acute forms of laminitis, which result in severe pain and the typical “sawhorse” stance, leaning back on the heels to relieve the pressure and discomfort in the toe area. Horses with severe laminitis also sweat heavily and will lie down to relieve the pain in their feet. The hooves will feel warm, and an artery ‘pulse’ can be felt behind the fetlock. There is a high risk that the pedal bone will rotate downwards and may break through the sole, or the hoof itself may detach from the pedal bone. If you observe these signs, consult your vet immediately.

Mild Laminitis:
In less severe forms of founder, the animal will stand, shifting weight from one foot to the other. If the hind limbs are more affected, the horse will stand with its front limbs back under to take more weight.

Subclincial Laminitis:
An American survey has recently suggested that many racehorses develop a low grade ‘subclinical’ form of laminitis. It was found that 46% of apparently sound horses had x-ray changes characteristic of laminitis. On x-ray the front hooves had evidence of slight pedal bone rotation, bony changes and curved or ‘flared’ out hoof wall. The horses with these changes also earned significantly less prize money than the affected hroses over a 6 month period.

A recent survey in Australia found that 16% of horses on high grain diets in a large racing stable had lower than normal faecal pH (hindgut acidosis) and symptoms indicative of subclinical laminitis. Some trainers are heavy grain feeders, and horses on these rations may be more prone to the subclinical form of laminitis.

Chronic Founder:
A horse or pony with recurring bouts of founder from season to season will develop a characteristic hoof shape with long toes, soft, wide white line area, flat soles, squashed heels and rings around the hoof wall. In long standing cases where pedal rotation has previously occured, the toe will elongate forward and the white line area becomes separated as non-pigmented hoof material attempts to bridge the lamina zone.

Because foundered horses continually lean back on their heels, the heels become compressed with appearance of parallel rings and the soles drop, leading to long term lameness and loss of use.

Diagnosis of laminitis
Diagnosis is a job for your vet to estimate the degree of laminitic separation, pedal bone rotation and collapse of the internal hoof structure. Typical clinical signs relative to the degree of laminitis, combined with x-rays taken from the side of the hoof wall will help confirm the severity of laminitis.

First Aid
Laminitis is an emergency condition and immediate treatment under the supervision of your vet is essential. If you know the animal has gorged on grain, advise your vet immediately, even if signs of laminitis are not present, as prompt therapy with a laxative drench may be required.

In the meantime, if laminitis is suspected:

1. Confine the animal to a stable or small yard. A sandy stall is ideal to allow the horse to stand as comfortably as possible. Do not walk a severely lame horse as further tearing and damage to the laminae will result. A severely lame horse may prefer to lie down – keep them propped up and cool the hooves as recommnded below until your vet arrives.

2. Cold water is now recommended over alternate hot and cold therapy. Hose the hooves with the horse standing on a soft, sandy area for 5-10 minutes, repeat every 10-15 minutes. Alternatively, wrap the hooves with plastic bags full of crushed or cubed ice for 5 minutes every 10-15 minutes.

3. Ask your vet if you should give a dose of Bute paste, to reduce the pain and laminae tissue swelling.

Treatment of laminitis
After a thorough examination and assessment of the horse’s history of predisposing causes, your vet will decide on the best form of treatment. The underlying cause of the condition will have to be treated as well as the inflammatory process within the feet. Anti-inflammatory drugs, sedatives, vasodilators and anti-clotting agents may be used in the treatment of the acute stages.

Hoof support is often applied to try to limit rotation of the pedal bone and other internal structural changes within the hoof. Support shoes which elevate the heels or ‘heart bar’ shoes which support the frog may be used. It is vital that these supportive shoes are correctly applied and regularly adjusted or they can cause excessive pressure and damage to the frog. In severe cases where shoes cannot be nailed on, support bandages or glue-on shoes may be used.

If the laminitis was feed induced, grain and lush pasture must be removed from the diet. Grass hay and white chaff (check that chaff does not contain oats or wheat grains) provide a high roughage, low soluble carbohydrate ration. This should be supplemented with a multivitamin and mineral supplement such as Feramo-H. Lucerne hay and chaff should be avoided, at least in the early stages of recovery, as lucerne can cause attacks of laminitis in some horses and ponies.

Calcium and biotin should be added to the feed for at least 6-12 months after an attack of laminitis to help promote hoof growth, prevent broken away hoof edges and prevent separation at the white line during recovery. Horses with laminitis should also be commenced on Founderguard to help prevent further episodes of laminitis, as recurrences are common following an initial attack.

In chronic cases, regular corrective trimming is essential. The aim is to lower the heel and square the toe to bring the hoof wall into alignment with the rotated pedal bone. An experienced farrier is highly recommended.

Prevention of laminitis
Founderguard is an Australian invention which has been a major breakthrough in the prevention of feed-induced laminitis. The product contains a low dose of an antibacterial-type compound that when given in the feed daily, helps to control overgrowth of the bacteria in the hindgut that produce lactic acid as they digest carbohydrate overload from grain or lush grass. It is available by prescription from your vet and must be given as a regular daily dose to provide full protection.

Founderguard does not protect horses against other forms of founder due to stress, concussion or severe infections.

Horses that benefit from Founderguard to prevent risk of laminitis include:

# Racing and performance horses on high grain diets, particularly those with ‘sore feet’ or show signs of low-grade laminitis

# Yearlings being prepared for sale, targeting those on high grain diets or where exercise is restricted due to lack of facilities to walk or lunge at the sale.

# All ponies, especially grey ponies or those with a previous history of grass founder. However, it is also wise to restrict grazing to avoid the animal becoming overweight.

# Horses recovering from laminitis to help prevent further occurrence.


Article courtesy of Dr John Kohnke from ‘Health Care and problems of Horses, 9th edition’ published by Virbac-Vetsearch.

Dr John Kohnke has over 20 years of experience in the health care and management of horses. He is well known for his ability to give sound, practical and up-to-date advice, which is sought by trainers and horse owners worldwide. As Technical Director of Vetsearch for 20 years, John had an opportunity to pursue research in equine nutrition, parasite control, lameness and respiratory problems.

For more of John’s articles, visit http://www.kohnkesown.com/

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