Founder and Laminitis Overview

Laminitis is a painful inflammation of the tissue within the foot that connects the hoof wall to the coffin bone. It can cause extreme lameness and may require euthanasia. It most commonly occurs in the front hooves. In severe cases, the coffin bone inside the hoof tears away from the hoof wall and rotates downward, causing a permanent need for corrective trimming and shoeing. This rotation is called founder.

The exact physical mechanism that causes laminitis is still somewhat of a mystery, but many of the triggers are well-known. For instance, ponies and easy-keeping or overweight horses tend to be most prone to laminitis when allowed to eat large quantities of lush grass. Particularly in the springtime, grass stores a sugar called fructan, which has been linked to triggering laminitis. Fructan levels vary widely in different types of grass, from region to region, throughout the year, and even throughout the day.

If your horse has a history of founder (which your veterinarian can determine by looking at and X-raying his hooves), he is much more likely to be predisposed to another bout of laminitis, so you should be particularly vigilant about limiting his turnout on grass or use a grazing muzzle. Turning him out in a dirt paddock (“dry lot”) with plenty of mature hay to munch on is usually the best solution for keeping him healthy.

In extreme cases, founder can necessitate euthanasia. The risk factors for laminitis and founder include obesity and excessive access to lush grass, particularly in spring when fructan levels are high. Understanding these triggers is crucial, especially for horses with a history of founder, as they are more susceptible to future episodes. Preventative measures, such as restricting grass access and providing alternative forage, are essential for managing the health of at-risk horses.

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This article originally appeared in the 2010 issue of Horses USA.