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Laminitis
Definition

The tissues that bond the hoof to the pedal bone are called the laminae and laminitis is a painful condition of the laminae. Acute laminitis refers to a recent onset of laminitis without further degeneration although acute laminitis can lead to tearing or separation of the laminae, progressing to tissue death and subsequent movement of the pedal bone within the hoof.This movement often results in rotation or sinking of the pedal bone relative to the hoof capsule. Chronic laminitis refers to these long-standing changes that follow acute laminitis. Laminitis is more common in the front feet and does not usually affect just one foot.

What can cause laminitis?

Laminitis is rarely caused by just one factor. In most cases the horse or pony has several predisposing causes which when combined have caused the pony to become laminitic.

Overweight horse
Obesity increases the risk of laminitis
Diagnosis

A diagnosis of laminitis can often be made from observable symptoms such as:

Another important test is the use of hoof testers on the sole of the hoof. Usually this will indicate sensitivity in front of the frog in the region of the tip of the pedal bone. Percussion (tapping) of the sole or shoe may also demonstrate increased sensitivity.

Radiography (x-rays) may also be necessary to assess the severity of the damage. Radiographs will indicate the position of the pedal bone within the hoof capsule. Tearing of the laminae is often indicated by a radiolucent (black) line between the pedal bone and front hoof wall.

Treatment

The first step to be taken is to remove any suspected cause for the laminitis. Removing predisposing causes for laminitis is essential. It usually involves bringing the horse or pony in from grass, reducing concentrates, and investigating and treating Cushings or metabolic disease. It some cases it may involve treating a serious underlying infection or restricting work on hard ground.

Veterinary attention should be sought to prescribe anti-inflammatory drugs such as bute or finadyne. Other medical treatment may also be used and this may be a drug such as ACP which modifies blood flow.

In more severe cases the vet may elect to remove the shoes and support the foot using a foot support system such as Styrofoam or Equisoft. The horse should be confined to a stable on a deep shavings bed to provide support to the pedal bone.

Subsequent to the treatment for an acute laminitic attack, remedial farriery may be used to provide ongoing support to the effected feet and to correct any imbalances that may have developed.

Prevention

Laminitis is a painful and distressing condition which can often be avoided with careful management. Although small ponies are most commonly affected, it is by no way exclusive to these breeds and any horse on lush pasture is at risk.

Awareness of the symptoms of subclinical (very mild) laminitis can assist in preventing development of the full blown clinical condition. Such symptoms can present as a horse which is repeatedly ‘jarred up’ or foot sore or the development of a shortened gait. Horses with a long toe/low heel conformation and a dished front hoof wall are at greater risk of developing the condition. Your farrier may notice crumbling and separation of the white line, seedy toe and increased sensitivity when nailing on the shoes.

Prognosis

Laminitis is an unpredictable condition and it can sometimes be difficult to make an accurate prognosis. Radiographs enable a more accurate prognosis to be given. In general, the longer a case goes without improvement, the poorer the prognosis.

Patients in which the laminar inflammation can be halted, and in which bony changes are minimal carry a fair chance of returning to athletic work given adequate time and the correct veterinary and farriery attention. If laminar tearing does not progress then the area of separation will eventually grow out and the foot can be re-balanced with the aid of corrective hoof trimming. Great care must be taken in subsequent years to prevent recurrence of the disease.

In the case of severe laminar damage the pedal bone drops within the hoof capsule. This is termed a ‘sinker’ and leads to a marked depression at the coronary band and convexity of the sole. The speed with which these changes occur is the most important factor in determining the outcome. Heavy horses carry a poorer prognosis as they are more prone to ‘sinkage’ of the pedal bone. Additional pressure on the tip of the pedal bone interrupts the blood supply to the bone and can cause the bone to die off.

Mechanism of carbohydrate overload induced laminitis

Sugars and starches are normally digested in the small intestine. Excessive quantities cause overspill into the large intestine. The bacterial population in the large intestine cannot digest simple sugars and carbohydrates but are biased towards digestion of complex carbohydrates. The overspill causes an overgrowth of certain alien lactobacilli species of bacteria which ferment the sugars instead of digesting them to useable products. This causes an acidosis to develop in the hind gut which inhibits the growth and existence of the good digestive bacteria. This drop in pH further favours the growth of abnormal bacteria which produce chemicals that lead to the production of metalloproteinase enzymes in the basement membrane of the hoof. These are responsible for the detachment of the laminae. Hindgut acidosis will manifest as sour smelling, loose faeces, development of a crumbly white line and poor hoof horn quality.

Where laminitic cases cannot be controlled by managemental means alone, hind gut acidosis can be controlled by the use of Founderguard, a supplement that prevents the overgrowth of undesirable lactobacilli. Probiotics without the addition of live yeast cultures can be added to the diet to boost the beneficial bacterial numbers to aid effective digestion and to compete with the undesirable bacteria.

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