As lush summer grass grows, unfortunately so does your horse's risk for laminitis, in which damage to the lamellae that attach the coffin bone to the hoof capsule causes instability within the foot, leading to compression of the soft tissue and the blood supply. Affected horses might have bounding pulses and heat within the foot, be reluctant to move or turn, and walk as if their front feet sting.

Pasture-associated laminitis can have a sneaky, slow onset. Owners often don't realize their horse has laminitis; they assume "he's a little sore on hard ground" or "stiff." Horses with insulin resistance or equine Cushing's disease are particularly at risk, as are horses that have suffered from laminitis previously. Consider the following suggestions to minimize your horse's pasture-associated laminitis risk:

Overweight horses are at risk for laminitis

  • Restrict pasture intake to help your horse lose weight. Limit turnout to two hours per day, but realize that horses can still consume a large volume of grass during that time. If your horse is turned out in a drylot, provide low-nonstructural carbohydrate (NSC <10%) hay at 1-1.2% of his body weight daily. Remove all grain, and use a low-calorie ration balancer for protein, minerals, and vitamins.
  • Turn your horse out in a grazing muzzle attached to a breakaway halter. Horses can still interact with the herd and exercise, but grass intake is limited.
  • Grass accumulates sugar (fructans) during cold, sunny days. Short, stressed grass also has a higher fructan concentration. Turn at-risk horses out on taller pasture for a limited amount of time in the morning. Avoid turnout after a frost.

Ask your veterinarian to test your horse for insulin resistance (IR) or Cushing's disease

  • Some IR horses are intolerant to pasture sugars, requiring permanent drylot turnout and low NSC feed.
  • Your vet might recommend drugs such as levothyroxine and metformin for IR horses, or pergolide to treat Cushing's.
  • These horses might have a history of laminitic flare-ups after vaccinations. Consider spacing vaccinations over several weeks, and avoid deworming simultaneously.
  • Reduce glycemic responses to feeding by giving low-carbohydrate grain and hay multiple times a day. Hay with less than 10% NSC is recommended. You can reduce NSC content by soaking hay in cold water for one hour, but keep in mind this might not completely lower the NSC content to a safe level.
  • If you harvest your own hay, start winter preparations early. To get low NSC hay, harvest nonstressed grass during warm nights, cutting during overcast mornings and allowing it to dry a couple days.
  • Exercise as soundness allows. Together, exercise and diet restriction improve insulin sensitivity.
  • Limit treats or substitute with sugar-free peppermints.
  • IR horses that need to gain weight can be fed soaked, non-molasses beet pulp (½-1½ lb/day), ½-1 cup vegetable oil daily, or a commercial fat pellet.
  • IR horses have abnormal insulin sensitivity; avoid using corticosteroids and intra-articular triamcinolone.

Consult your farrier and veterinarian about monitoring the feet

  • Annual baseline radiographs help the farrier balance the foot, determine sole depth, assess the coffin bone's condition, and monitor for any laminitic changes.
  • Growth rings on the hoof walls should be uniform from the toe to the heel.
  • The white line should be narrow at the toe, not wide and seedy (indicates lamellar damage).
  • The sole should be cupped, not flat or dropped.
  • Maximize hoof mass: Strive for feet with strong walls and a heavy sole.

To prevent pasture-associated laminitis, the owner-farrier-veterinarian team should work together to identify at-risk horses. Owners of horses that have had previous bouts of laminitis must be especially diligent in their management to prevent further foot damage. While the greatest opportunity to successfully treat laminitis occurs at the onset of disease, prevention is ideal.

About the Author

Amy Rucker, DVM

Amy Rucker, DVM, works in the equine ambulatory practice in the College of Veterinary Medicine at the University of Missouri-Columbia.

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