Laminitis is one of the most distressing conditions that can face horses and their owners. Sadly it is also extremely common, reportedly affecting 7.4% of horses/ponies at some point in their lives.
What is laminitis?
Laminitis, in its simplest form, is inflammation of the sensitive layers (laminae) of the hoof. The pedal bone is suspended within the hoof by many interdigitating specialised ‘leaves’ (laminae) composed of sensitive tissue. In laminitis these soft tissues become damaged resulting in pain, inflammation and, in some cases, the formation of gaps between the laminae. In very mild cases, appropriate treatment will resolve the problem quite quickly with no lasting effect. If the inflammation is more severe and progressive, the sensitive laminae may loose their blood supply and die with consequent loss of support between the pedal bone and horny hoof wall. This can result in separation of the pedal bone from the hoof with rotation and/or sinking of the bone within the hoof. As the horse stands and moves on its feet, penetration of the sole by the tip of the pedal bone can follow, with fatal consequences. Even in chronic cases, gradual rotation of the pedal bone can cause irreparable damage to this bone with increasing levels of pain and distortion of the hoof.
What causes laminitis?
Laminitis may occur as a consequence of 3 broad categories of disorders:
How can I recognise laminitis?
In mild cases of laminitis, the horse or pony may appear slightly ‘pottery’, especially on hard ground. The forelimbs are most commonly affected although it is possible for the hindlimbs only or all four feet to be affected.
The affected foot or feet may appear abnormally warm to the touch and the pulse taken at the heel’s arteries may appear particularly strong. Laminitic horses will often stand with hindlimbs well under the body and forelimbs stretched out in front, in an effort to keep weight off the painful front feet. This characteristic stance is almost diagnostic of laminitis.
Affected horses will move with their heels landing first to try to avoid concussion to the painful toe region. If all four feet are affected, they may lie down for long periods or may constantly lift their feet alternately from the ground. More severe cases result in sudden inability or reluctance to move at all and horses with severe rotation and sinking will often be unable to bear any weight on the affected limb or limbs and will lie down.
What can be done?
Acute laminitis is a medical emergency and treatment should be initiated as soon as possible, so it is very important that you contact your vet immediately if your horse exhibits any of the signs mentioned above.
On initial presentation your vet will confirm whether it is laminitis and will try to determine the underlying cause if possible. Further tests are performed in those cases where an underlying hormonal abnormality is suspected, as this will greatly affect the management and the likelihood of the return to soundness. Your vet will suggest which tests are most appropriate following the detailed clinical history of the horse.
By the time the clinical signs of acute laminitis become apparent, the lamellar tissues have already been damaged, so the therapy is aimed at providing analgesia (commonly provided with use of non-steroidal anti-inflammatory drugs, e.g. Phenylbutazone) and foot support.
Supporting the foot is an essential part of the management of acute laminitis. The horse naturally adopts a stance that allows most of the weight to be borne over the caudal part of the foot rather than the painful toe region. Providing additional support to this region of the foot will provide pain relief and also help to minimise the mechanical forces on the laminae. The simplest strategy is to increase the depth of the bedding and ensure that the bedding extends to the door. Shavings, sand, peat or hemp-based products are optimal as they pack beneath the feet better than straw or paper. Frog and sole support can be also provided using, for example, dental impression material that is moulded to the contours of the caudal two thirds of the foot or Styrofoam pads that are crushed by the weight of the horse. Alternatively, a commercially available product such as the lily pad or Newmarket frog support can be used.
Once the acute phase is finished, radiographs are taken to assess the position of the pedal bone within the hoof capsule. Breakdown of the attachment between the sensitive and insensitive laminae can result in the pedal bone either sinking or rotating with the hoof capsule under the weight of the horse and/or due to the direction of pull from the digital flexor tendons. The degree of pedal bone rotation and the founder distance is then calculated, and the radiographs are forwarded to the farrier so he can perform optimal corrective trimming and shoeing. There are several types of shoes that can be used (for example wooden clogs, heart bar shoes, wide web aluminium rail shoes, etc.) and your farrier will choose the most appropriate shoe for your horse after seeing the radiographs (taking into account degree of rotation, depth of the sole, etc). The ground surface of the frog and sole can also be supported under the shoe by pads or by a synthetic composite.
The radiographs are then usually repeated in regular intervals until the physiological state of pedal bone and hoof capsule is achieved. A close liaison between your vet and your farrier is paramount in these cases.
Initial radiograph: there is 8o rotation of the pedal bone;
the dark space between the hoof wall and the pedal bone
is consistent with lamellar tearing (horses can often develop
an abscess here if not treated)
Follow up radiograph: after correct trimming the foot is in
much more physiological position and the rotation is reduced to 6o
What can we do to prevent further laminitis?
Prevention is much better than cure and most, although not all, cases can be prevented by good management, including regular skilled farriery.
It is important to find out the initiating cause as this will greatly affect the management of the horse.
Most effective medical treatment is with pergolide (Prascend), which reduces the effects of the disease centrally (in the brain); the medication helps to prevent further laminitis and some of the clinical signs of the disease. However, it cannot stop the further development of the disease (thus eventually increase of the dosage will be necessary)
Nursing and diet
Horses have a debilitated immune system, therefore it is very important to be vigilant and treat any secondary infections (e.g. they commonly suffer with internal and external parasitism, dental problems) as soon as possible.
Clipping of coat hair to prevent excess sweating.
Careful attention to diet (good quality diet with sufficient vitamin and mineral intake).
Management of EMS involves management of the underlying metabolic disorder of insulin resistance and management of laminitis. Detection, monitoring of and reduction of the obesity is a major aim:
Dietary management involves reduction of total caloric intake as well as the non-structural carbohydrate intake. Mild cases of seasonal laminitis may only require seasonal pasture restriction, while severe cases of EMS may require a strict weight loss programme
In all cases, the first step is to remove all grain-based concentrates from the diet (including treats!)
Feeds containing high non-structural carbohydrates have been shown to induce more insulin resistance than other feeds in horses. Pastures can be very high in non-structural carbohydrates, especially spring pastures, and even when dried into hay or haylage can still be very high. Pasture access restriction is usually required.
Soaking hay has been shown to reduce the starch and sugar content. Regardless of the soaking time, there is always a loss of calories from the hay; however the longer the leaching time the greater the loss and 12 hours is often recommended so that the owner can still feed up to 2.5% bodyweight to minimise the welfare consequences of reduced dry matter intake.
To calculate the amount of total forage fed to induce weight loss in an obese horse, the initial aim is to feed 1.5% of the horse’s body weight. If this is insufficient this can be reduced to 1% of bodyweight, however this should be monitored carefully. With severe feed restriction some horses may develop behavioural changes.
It is important to ensure the horse has adequate protein, vitamin and minerals as a forage-only diet, especially with soaked forage, will not provide adequate amounts of these nutrients. A low calorie commercial ration balancer will need to be also fed (e.g. Dodson & Horrell Ultimate Balancer).
Exercise is extremely important in managing EMS as it helps to improve insulin sensitivity and reduce hyperinsulinaemia, and it helps reduce weight in obese horses
Your vet/farrier will advise you when the hoof lamellae are strong enough to withstand exercise – do not force your horse to exercise in early stages of laminitis!!
Exercise can be commenced on a soft surface, ideally sand school, and gradually increased with close monitoring for worsening of lameness
Exercise intensity does not have to be high, but the aim is for consistent exercise of 30 minutes or more daily once the hooves are stable
Medication, such as Metformin are prescribed in some cases of EMS with the hope to increase insulin sensitivity; however, there have been mixed results seen and the response to this medication is very individual
Laminitis can present with signs varying from being slightly ‘pottery’ to a life threatening condition and should never be treated lightly. Even mild cases can take many months to improve and some horses never regain full soundness. Significant numbers of cases of acute laminitis, associated with toxaemia cannot be saved, even with high quality intensive care.
Prevention is much better than cure and most, although not all, cases can be prevented by good management, including regular monitoring (blood testing) and skilled farriery.