Grass Founder in Horses
Lush spring pastures can be dangerous temptations for horses.
By Dr. Tom Lenz in The American Quarter Horse Journal | May 20, 2009
Spring is upon us. As lush, green grass begins to grow, it could be the beginning of serious founder problems – laminitis.
Laminitis is inflammation of the laminae of the horse’s foot. Laminae make up the delicate, accordion-like tissue that attaches the inner surface of the hoof wall to the coffin bone (the bone in the foot.) The sensitive laminae cover the bone and interlock with the insensitive laminae lining the inside of the hoof wall to keep the coffin bone in place within the hoof.
A horse suffering from laminitis experiences a decrease in blood flow to the laminae, which in turn begin to die and separate. The final result is hoof wall separation, rotation of the coffin bone and extreme pain. In severe cases, the coffin bone can actually rotate through the sole of the horse’s hoof where it becomes infected and usually results in the death of the horse.
Laminitis is triggered by a variety of causes, including repeated concussion on hard ground (road founder); grain overload; retained placenta; hormonal imbalance (Cushing’s disease or metabolic syndrome); certain drugs (corticosteroids); obesity; and lush grass.
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Veterinarians and nutritionists have known for some time that plants store energy in their seeds in the form of starch that can cause laminitis if the horse is introduced to grain too quickly or eats too much grain. Only recently have researchers discovered that grasses not only store energy in their seed heads as starch, they also store energy as sugar.
In the spring, as grass is growing rapidly, it stores more sugar than it needs for growth, and horses consume the sugar as they graze. Later in the year, when the daylight and nighttime temperatures are more consistent and grass growth rates decrease, the plant uses up most of the sugar produced during the day each night.
Here are some tips for avoiding grass founder:
- Keep horses off lush, fast-growing pastures until the grass has slowed in growth and produces seed heads.
- Graze horses on pastures containing a high percentage of legumes. Legumes, such as alfalfa or clover, store energy as starch, not sugar.
- Avoid grazing horses on pastures that have been exposed to bright sunny days followed by low temperatures, such as a few days of warm sunny weather followed by a late spring frost.
- Avoid grazing horses on pastures that have been grazed very short during the winter and are growing rapidly.
- Keep overweight horses in stalls or paddocks until the pasture’s rate of growth has slowed, then introduce them to pasture slowly.
- Turn horses out on pasture for a few hours in the early morning when sugar levels are low, not at night when levels are at their highest.
- Allow horses to fill up on hay before turning them out on grass for a few hours.
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Horses that are over the age of 10, “easy keepers,” overweight or those with crested necks seem especially vulnerable to grass founder and should be the focus of your preventive program.
After the horses are turned out on pasture, check them often for early signs of laminitis such as heat in the feet and a pounding pulse at the back of the pastern. Foundered horses also assume a characteristic “sawhorse” stance with their hind feet up under their body and their front feet placed farther forward than normal. This is because the horse is trying to shift its weight off its painful front feet to its hind legs.
Grass-foundered horses also move gingerly, as if walking on eggshells, and are often unwilling to turn or move at all. In severe cases, the horse may refuse to stand. If your horse demonstrates these signs after being turned out on grass, immediately pull him off the pasture and call a veterinarian.
If you have horses that are prone to grass founder, visit with your veterinarian or equine nutritionist to develop a strategy for introducing them to spring grass. This is truly a situation where an ounce of prevention is worth a pound of cure.