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Grazing horses prone to laminitis

Quick facts

  • High amounts of sugars in grasses can bring about laminitis in horses susceptible to the disease
  • Many factors affect the amount of sugar in forages
  • Susceptible horses should have limited grazing or no grazing

If you want to graze a susceptible horse:

  • Graze between 3 a.m. and 10 a.m.
  • Carefully select pasture plants
  • Watch the weather
  • Don’t overgraze pastures
  • Use a grazing muzzle
  • Keep the horse in shape
  • Work with a veterinarian and nutritionist

Is your horse prone to laminitis?

High sugars or fructans found naturally in Minnesota forage species can trigger pasture-caused laminitis (founder) in susceptible horses. Susceptible horses include, but aren’t limited to:

  • Overweight, easy keeping horses
  • Ponies
  • Horses with metabolic syndrome
  • Horses that have foundered before

Grazing susceptible horses

Susceptible horses should have limited grazing or no grazing at all. For extremely sensitive horses, there is no completely safe time to graze. Not all horses need to follow these recommendations, but susceptible horses should. Grazing during these times or scenarios doesn’t guarantee the sugar content will be lower.

When should susceptible horses graze?

Susceptible horses should graze when forages are lower in sugar. Many factors affect the amount of sugar present in forages including:

  • Weather
  • Plant stress
  • Species maturity (the plant’s stage of growth)
  • Time of day
  • Time of year

During daylight hours, grasses make and store sugars as they take in water, sunlight and carbon dioxide (photosynthesis). Plants use sugar to fuel growth overnight. So plant sugars are higher in the late afternoon and lower in the early morning. Susceptible horses should graze between 3 a.m. and 10 a.m., when plant sugars are lower.

Plants collect sugar in times of stress such as during a drought or when temperatures fall below 40° F. Don’t graze susceptible horses during periods of plant stress.

Minnesota’s cool spring and fall weather may also cause plants to collect sugar. This may increase the risk of pasture-caused laminitis for susceptible horses. Warmer weather or dark periods (night hours or cloudy days) offer better times to graze as plants are using sugars for quick growth.

Overeating

Overeating can still cause disease in susceptible horses. Horses grazing in areas shaded by trees or buildings may be able to graze longer as plants will be collecting less sugar. Allowing pasture grasses to become more mature should also reduce the sugar content and result in less (and a slower) eating.

Grazing muzzles

If grazing is your horse’s main source of exercise, consider using a grazing muzzle. Grazing muzzles limit the amount of forage a horse can eat.   

Pasture species

Some pasture species are more likely to collect sugar under stressful conditions than others.

Species more likely to collect sugars include:

  • Timothy
  • Bromegrass
  • Orchardgrass
  • Most cool season grasses in Minnesota horse pastures

Most forage species store sugars in the bottom 34 inches of growth. Making sure pastures are not overgrazed will help avoid laminitis. Correctly fertilize pastures and avoid grazing susceptible horses during times of plant stress.

Exercise

Regular exercise and good body condition will help lower the risk of pasture-caused laminitis.

Krishona Martinson, Extension equine specialist

Reviewed in 2018

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