By Sarah Eaton, DVM, DACT
Spring is here and with it comes the fresh green grass that horses love to over-eat on. While the grass looks pretty and is very delicious, it can be harmful to horses because of its high sugar content. When horses gorge on green grass they are prone to laminitis, also known as ‘founder’.
Laminitis is a potentially fatal disease that is due to inflammation of the tissue between the coffin bone and the hoof wall. Laminitis is most commonly triggered by the high sugar levels in green grass, but can also be triggered by obesity, stress, and illness.
Alterations in nutrition or metabolism lead to an increase in the blood flow to the foot. This increased blood flow is responsible for the increase in digital pulses one can feel over the heels and the heat of the hoof. To check for increased digital pulses, feel the back of the pastern, just above the heel bulbs. A normal digital pulse should be difficult to feel without a mild amount pressure. Elevated or bounding digital pulses feel similar to feeling a person’s jugular pulse on their neck.
Some medical conditions such as Cushing’s disease or Insulin resistance can predispose animals to laminitis. Horses that develop laminitis due to pre-existing health conditions must be managed in two ways; by treating the underlying disease and by treating the laminitis.
Clinical signs of laminitis include unwillingness to move or turn, ‘walking on eggshells’, standing while tilted back, and laying down a lot. In cases of acute laminitis there is active inflammation in the foot which can lead to rotation or sinking of the coffin bone. In horses with rotation the tip of the coffin bone tilts toward the ground and if severe enough can puncture the sole of the hoof.
Sinking occurs when all the attachments of the coffin bone to the hoof capsule become inflamed and allow the bone to drop within the hoof. The changes in the foot can occur slowly (over weeks) or very rapidly (over hours).
Veterinarians can use radiographs (x-rays) to assess the position of the coffin bone in the hoof and monitor changes. Radiographs can also help to determine the best trimming or shoeing protocol for affected horses. Horses with chronic laminitis have stable, ongoing disease that may flare up into acute laminitis. Horses that have suffered bouts of laminitis have characteristic rings around their hoof wall that tend to be more stretched at the heel.
Treatment of acute laminitis is aimed at eliminating the predisposing causes and preventing its progression. If on lush pasture, a horse is removed from the pasture and usually placed on a diet. The horse is encouraged to lay down by confining it to a small, well-bedded area. Aggressive anti-inflammatory therapy is instituted to help the horse be more comfortable, encourage it to stand normally, and decrease the inflammation in the affected feet. Special pads, boots, or shoes can be applied to help the horse stand more comfortably and try to reduce movement of the coffin bone.
Management of chronic laminitis horses involves lifestyle changes such as dry lot turnout, consistent exercise (if the lameness level allows), and special trimming or shoeing. By working with your veterinarian you can develop the best plan to prevent your horse from developing laminitis or worsening chronic disease.
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