This article has been published previously by Equestrian Life. To see what's in our latest magazine, click here.

When it comes to laminitis, there are a number of underlying causes.

© Andrew Bowe

By David T.Wood BVSc.MRCVS.

Part 2

Underlying Causes

At the heart of the problem is a degradation of the “basement membrane” which is the surface of attachment between the sensitive and insensitive laminae of the hoof. This specialised cell layer covers the gap between the two sorts of laminae which at the microscopic level resemble Velcro.

Broadly speaking we can distinguish two main causal types, hormonal and inflammatory.

Inflammatory causes:

Carbohydrate overload. Generally involves either excess Starch from grains or Fructan from pastures, or both in combination. When these carbohydrates enter the large intestine in sufficient quantity they cause a change in the normal balance of micro flora residing there. In particular there is an overgrowth of Gram positive Streptococcus species which produce acid. This acid lowers the gut pH causing diarrhoea and damages the intestinal lining. Bacterial toxins normally found inside the bowel leak into the circulation and are thought to be implicated in causing laminitis, either alone or in conjunction with Fructan, a polysaccharide found in pastures.

Sepsis. Infection of another organ such as the lungs ( pneumonia ), bowel, or uterus, especially post foaling, can provide a source of bacterial toxins entering the bloodstream with similar results.

Hormonal causes:     

In the past few years it has been shown that high blood Insulin levels can cause Laminitis in horses. Insulin Resistant ( IR ) horses are predisposed to Laminitis as are those with Equine Metabolic Syndrome ( EMS ) and Cushing’s Syndrome. It seems that this is a direct effect on the lamellar tissues in the hoof, independent of the inflammatory causes mentioned above. In these horses there may be no associated large bowel inflammation or other site of toxin production.

However, what seems clear is that these IR horses are more susceptible to Laminitis resulting from Fructan overload from pasture. The IR reduces their ability to control blood sugar levels and results in a high resting insulin level. When challenged by high fructan loads, the already high blood insulin spikes even further and Laminitis may result.

Other causes:

Laminitis has been associated with direct trauma to the foot, for example from excessive hard road work “Road Founder”, over trimming the sole of the foot, hoof infections and swelling of the legs.

One specific type is called “Contra Lateral Limb Laminitis” where pain and lameness in one leg, from a fracture for example, results in excessive weight being borne on the same leg on the opposite side, eventually resulting in a type of inflammatory laminitis.

David T.Wood BVSc.MRCVS.

David is a veterinary surgeon with 35 years equine experience gained in several countries. For the past 20 years he has pursued a special interest in equine nutrition and currently acts as veterinary and technical advisor to Horsepower. 

This article has been published previously by Equestrian Life. To see what's in our latest magazine, click here.

Read "No Foot No Horse" Part 1.

READ THE LATEST NEWS ARTICLES HERE