While fresh green spring fields are beautiful to look at, new, thick lush grass can also be dangerous. Pasture associated laminitis is a problem veterinarians see every year after the growth of grass in the spring. In cases of laminitis, the lamina separates between the pedal bone (P3) and the inner hoof wall causing unrelenting pain and characteristic lameness. It is the most serious disease of the equine hoof that leads to devastating loss of function and sometimes loss of the horse. While there are many different conditions that can lead to laminitis, pasture associated laminitis, or “grass founder” can be traced back to the high sugar content of the grass, specifically the fructans.

Signs

• Lameness (one or both front feet are most commonly affected)
• Reluctance to walk
• Increased digital pulses
• Continuously shifting weight from one leg to another
• Sitting back on their haunches, front limbs stretched in front of them
• Crouching on the haunches and swinging front legs around to make a turn
• Laying down excessively
• Unable to stand

Causes

When a horse takes in a large meal containing sugars, they develop a temporary inflammatory condition in the GI tract called “carbohydrate overload.” Starch and sugars are normally digested and absorbed in the stomach and small intestine. The transit time through this portion of the GI tract is about 90 minutes and with a balanced meal, most of the carbohydrates will be absorbed before the feed passes into the cecum and large colon. However, if the meal is too high is sugars, too many sugars enter the small intestine and instead of being properly absorbed, some pass through to the large colon. This leads to a shift in fermentation and acidity of the colon contents and allows dangerous toxins to leak out of the gut into the bloodstream. There is also a large spike in glucose and insulin in the blood stream.  These toxins, inflammatory substances, glucose and insulin reach the hoof and contribute to the formation of laminitis. Prevention of pasture associated laminitis can be as simple as limiting your horses’ access to lush grass.

Diagnosis

• Evaluation of gait, usually just at the walk
• Examination of the hooves, including a hoof tester exam
• Radiographs of the feet to determine if any rotation or sinking has occurred

Treatment

Treatment of laminitis can be a difficult and frustrating task that requires cooperation between your veterinarian and your farrier. Solar support can be placed in the form of foam pads, impression material or corrective shoeing. Horses should be restricted to the stall or a very small paddock to limit movement and further damage to the feet. New research shows that cryotherapy can prevent some of the structural damage. This can be achieved by having horses stand in buckets of ice water or placing commercial ice boots on their limbs to lower the temperature of the tissue in the hoof. Deep sand or sawdust bedding will increase their comfort.

Prognosis and Prevention

Prognosis depends on the severity and chronicity of the laminitis. Some horses can recover and return to full athletic activities while other horses may only be pasture sound. Unfortunately many horses have to be euthanized do to the severity of disease and pain.

The following suggestions are just a few things you can do to prevent pasture associated laminitis and keep your horses happy and sound throughout the spring and summer. 

• Identify the horses and ponies that are at a higher risk of developing laminitis. Test “easy keepers,” geriatric horses and those with a history of laminitis for EMS and / or Cushing’s Disease.
• Treat any predisposing condition with diet, exercise and proper medications.
• For horses with a lower threshold, consider a zero grazing environment, such as a dry lot (while providing the horse with suitable forage alternatives).
• Limit turnout of pasture when grass is lush and when fructans are high.
• Turn horses out to pasture when fructan levels are likely to be at their lowest, such as from late night to early morning, removing them from the pasture by mid-morning.
• Employ the use of grazing muzzles to allow horses out on pasture but still limit their intake of grass.
• Maintain pastures regularly to prevent grass from becoming mature and stemmy (they contain high levels of fructans).