Laminitis is not only one of the most common causes of lameness, but it also responsible for a large number of equine deaths. Yet the causes of this devastating disease are still misunderstood by some owners, and as a result many horses and ponies are being put at risk.
The condition occurs when the blood supply to the sensitive laminae, which lie between the pedal bone and hoof wall, is disturbed, and a subsequent lack of oxygen and nutrients causes the cells to wither and die. As the hoof wall cannot expand to accommodate the inevitable inflammation of these tissues, the horse experiences great pain. Once the laminae begin to weaken they are no longer able to cling on to the pedal bone, and this leads to tearing within the structure of the foot. Unless this process is halted, the pedal bone will begin to drop and rotate - a serious condition that is referred to as 'founder'. In severe cases the pedal bone may pierce through the sole.
So what causes laminitis? The term is usually associated with the image of an obese pony that has been given access to a field full of long, lush grass. However, whilst laminitis is most commonly seen in small ponies, especially at a time when the grass is growing rapidly, to attribute it to these two factors only would be a dangerous and faulty assumption: horses are also susceptible, and there are a number of triggers.
It is known that laminitis is set off by a build up of acid in the hind gut, usually caused by a rapid fermentation of carbohydrates. Therefore, excessive amounts of cereals can do as much damage as grass, and many horses that have been fattened up with hard feed in order to be brought into 'show condition' have come down with the disease.
Whilst grass is inextricably linked with many cases of laminitis, it is the high levels of Fructan produced within the plant that are to blame. As these carbohydrates are stored in the stems rather than the leaves, stressed pastures can be more dangerous than overgrown ones: grass does not have to be long to be hazardous. Fructan levels become particularly high when warm days are followed by cool nights, and owners should avoid putting susceptible animals into frosty paddocks on spring mornings. Fields that have been recently cropped for hay also carry a high risk as horses have direct access to the grass stems.
Large doses of corticosteroids - an anti-inflammatory drug sometimes administered to deal with conditions such as recurrent uveitis or arthritis - can also cause laminitis. Moreover, as the equine adrenal gland will release natural corticosteroids into the body as a response to stress, traumatic situations can also be responsible for triggering the disease; for instance, it has not been unknown for episodes to occur in horses that have travelled a long distance. Cushing's disease, a condition of the pituitary gland that affects older horses, is another common cause and accounts for a high number of cases.
Laminitis can also arise as a result of repeated concussion - too much trotting on roads or riding on hard ground are prime examples of how this can occur. Horses that have been forced to bear excessive weight on one leg as a result of injury have also suffered from the disease as a result. Other medical problems such as infection, retained afterbirths and colic can also put horses at risk.
Being able to recognise the early signs of laminitis is absolutely vital if rotation of the pedal bone is to be prevented, as treatment will be needed within the first 24 hours. During the preliminary stages of the condition the horse may simply demonstrate a short, shuffling gait that will progressively worsen with exercise and be more obvious on hard ground. Whilst it is the fore-feet that are most commonly affected, and usually as a pair, one or both of the hind feet may also suffer, particularly if the episode is as a result of excessive weight-bearing on one leg.
As the disease takes hold the horse will show acute lameness and may refuse to move at all. A large number of sufferers appear locked to the ground, with the hind feet pushed underneath the body and the forefeet thrust out in an attempt to take weight off the toes. A laminitic horse may also transfer his weight from one foot to the other repeatedly, and his hooves may feel hot. There will be particular heat around the coronary band, and palpitation of this area will induce pain. The digital artery that supplies blood to the foot will be pounding - this can be felt by laying two fingers against the site of the artery on the inside or outside of the pastern. The horse may have an increased heart rate, darkened mucus membranes and shortened breath.
An emergency vet must be sent for immediately, and a wrapped, rolled bandage should be taped onto each of the frogs of the fore-feet to give temporary support. The horse will need to be moved (very carefully) into a large stable, by means of a low-ramped trailer if necessary. He should be provided with a deep bed of shavings, and whilst he may be allowed to lie down he should not be left unsupervised until the vet arrives.
Contrary to old-fashioned belief, a laminitic horse should never be starved, have exercise forced upon him, or have his shoes removed. His diet will need to be managed diligently, and your vet will provide strict instructions on this crucial aspect of care. He or she will also administer drugs, perform a radiograph to ascertain the position of the pedal bone, and fit specialised frog supports. Attention to veterinary advice is imperative.
Nursing a laminitic horse is a time-consuming but necessary job. Twenty to thirty percent of cases suffer extensive damage to the laminae; in such circumstances, the horse may be able to enter retirement if he is lucky, but euthanasia is sometimes the only option. Nonetheless, if laminitis is recognised and treated in time the horse can be brought back to full health - but he will always be susceptible to the condition.
Needless to say, laminitis should be avoided at all costs. The uptake of the following preventative measures will be far less time consuming than dealing with the illness once it arises.
Never feed large amounts of high-energy cereals, particularly to native ponies whose metabolic systems cannot cope with such a diet. This type of animal should never be put out onto lush grass either, even if he has no history of laminitis. Always make all changes to diet gradual, whatever the type, size or breed of your horse, and make sure that the correct quantities of fibre are being fed.
Attention must be paid to the rate of grass growth, especially during spring and autumn. Enforce grazing restrictions accordingly by using strip grazing, muzzles or stabling, and be sure to take the weather conditions into account. Particular care must be taken when the days are warm and the evenings cool, and remember that short grass, particularly on stressed pastures, can also be a killer.
Manage your horse's weight appropriately, and measure his girth at regular intervals. Be sure to keep paddocks free of manure, and implement an effective worming programme. If your horse or pony has suffered from digestive disorders such as colic, has developed Cushing's disease, or has gained access to large quantities of food, he or she will be at particular risk of laminitis and should be monitored accordingly.
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