BLACKSBURG, Va. – With the grass now growing rapidly, some horses are in danger experiencing pasture-induced laminitis. Though the words laminitis and founder have been used interchangeably, they are not the same thing.
Different. Laminitis is an inflammation of the sensitive tissues within the hoof structure; founder references the actual rotation of the coffin bone.
Not all horses that experience laminitis founder, but any horse that has foundered has experienced laminitis. Over-consumption of nonstructural carbohydrates can result in laminitis.
Nonstructural carbohydrates include sugars, starches, and fructans, and are found in variable levels in pasture forages depending on many variables, such as forage species, season and time of day.
Young, rapidly growing forages tend to be higher in nonstructural carbohydrates than older, more mature forages.
Studies at Virginia Tech’s MARE Center found that forage nonstructural carbohydrates were highest in April, May and August, and those concentrations peaked in the afternoon. Ponies are particularly prone to laminitis, as are overweight or insulin-resistant animals and horses with Cushing’s disease.
Symptoms. Symptoms of laminitis may include the classic “founder stance,” where the horse stands with the hind feet well up under the body and the forefeet extended in front; walking very tenderly; increased temperature in the feet; lying down excessively; and other signs of pain (sweating, trembling, anxiety).
If the episode of laminitis is mild, the horse may recover with no apparent lameness. If the horse founders, however, the rotation of the coffin bone can never be corrected. In mild cases of founder, therapeutic shoeing may allow the horse to walk comfortably or even continue performing.
In severe cases the horse will never be sound again and may have to be euthanized.
Suggestions. Regardless, horses or ponies predisposed to laminitis should have limited access to pasture forages during the spring months.
Introducing animals to lush pasture forages should be done slowly, starting with only an hour or so at first and gradually lengthening their time on pasture as their digestive system adapts to the rich feed.
Turning them out to graze late at night and early in the morning is safer than having them out during the day or early evening. Also, feeding the horse before turning them out may help keep them from over-consuming young, spring grass.
Using grazing muzzles will also limit intake while still allowing the horse to be turned out for exercise and companionship.
In severe cases, laminitis prone animals should be placed on a drylot and fed hay while pasture forages are rapidly growing.
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