Dr. Kimberly Brokaw, DVM
(6/2015) Nothing seems quite as relaxing as sitting in the porch, drinking lemonade, and watching horses graze on a lush green pasture. However, an abundance of lush green grass cannot only permanently lame your horse, it could even kill him. Ask your average kid "what do horses eat?" and the answer they give is "grass". Your average person thinks that
horses can live on grass alone and that the only danger from too much grass is that the horse might get fat. Even some experienced horse owners don't always realize just how dangerous a lush field can be.
Laminitis (or founder) is one of the most serious and crippling diseases of horses and ponies. This painful inflammation leads to tearing of the support structure that suspends the bone in the hoof capsule. This can result in the bone separating from the hoof wall and either rotating or sinking. In severe cases the bone can penetrate through the hoof
and the horse almost always has to be euthanized. Even mild cases of laminitis can be very painful for the horse and leave him more susceptible to future episodes. Laminitis can be treated, but treatments are often expensive and life-long.
Laminitis can be triggered by many factors. Illnesses, such as Potomac Horse Fever or severe colic, can cause severe laminitis. Metabolic diseases like Cushings and insulin resistance make a horse more prone to laminitis. Medications such as steroid injections can trigger laminitis. Toxic plants, such as red maple leaves, are a cause of laminitis.
Injury to a leg can cause a supporting limb laminitis in the foot that is bearing extra weight while the horse tries to keep weight off the injured leg. However, lush spring grass is probably the most common cause of laminitis.
Every spring, I see a number of cases of laminitis in horses who have been out enjoying their suddenly green grass. Lush grass sometimes has more sugar than a horse can tolerate. If a horse eats more sugar than he can tolerate, the cascade of laminitis begins. Grass related laminitis is particularly a problem in ponies and breeds of horses who are
"easy keepers" who gain weight easily, as well as horses who are not in regular, hard, work. Older horses, who have Cushing's syndrome, are quite prone to laminitis related to eating too much sugar in their grass. Countless horse owners struggle with the balance of wanting to have fields that are attractive to look at and covered in grass rather than mud, yet are not
providing too many calories and too much sugar for their horses. Deciding how much grass a horse can tolerate is a juggling act. Horses want to gorge themselves on grass. There is no easy formula for figuring out exactly how much grass an individual horse can eat without causing a problem.
One of the large barns that I work for is managed by a group of well educated, animal loving, people. Some of the people in this group are casual horse owners that aren't the most knowledgeable about equine nutrition. They decided that they wanted all the pastures to be lush and green. The horses were kept off the fields and the fields were
professionally seeded and fertilized. The grass came in beautifully. All the fields were beautiful with not a single bare patch. A dozen of the horses developed laminitis the first spring with several others developing it throughout the year. Two of them will likely never be rideable again. Radiographs showed that some of the horses had mild rotation of the coffin bone with
others having more severe rotation.
Cupcake, who had been one of the favorite horses, was most severely affected. Her coffin bone rotated and there was minimal amount of sole between the bone and the ground. She spent months in a deeply bedded stall with her students grooming, and petting her, but was too painful to leave the stall for more than a couple hours a day. After thousands of
dollars of medication, radiographs, and corrective shoes, she is just now starting to return to "pasture sound". While I doubt she will be rideable again, 2 years after her initial laminitis episode, she is at least comfortable enough to walk and trot.
After seeing multiple horses at the barn with laminitis, I requested that the farm have several dirt paddocks built and the horses be pulled off the grass and only turned out in those paddocks. I also jokingly suggested that perhaps the barn should spray Round-up on all their pastures and kill the grass. While the barn management did not approve of
killing all the grass, they did consent to building lots of small pastures that the horses could keep eaten down. This method has resulted in healthy horses on dirt paddocks as well as beautiful fields for the board of directors to look at yet not to be used by most of the horses.
While prevention is best, if you think your horse has laminitis, call your vet. The vet can prescribe medications to reduce inflammation and provide pain relief. They can also advise you on a nutrition plan for your horse as well as consult with your farrier for therapeutic shoes or trimming. While most horses never fully recover from laminitis there
are many treatments to try to help them become sound again. This is one of those disease where prevention is best. So while most people would prefer to look at fat, shiny, ponies grazing in a pasture of long, green, grass, sometimes a dirt lot may be healthier for your horse.
Read other articles by Dr. Kim Brokaw