Laminitis and Controlling Spring Pasture Access

Horses might be as eager to get out in the sunshine as we are to break out the shorts and T-shirts, but after a winter cooped up in a stall eating hay, don't give them free rein to that scrumptious spring pasture just yet.

According to Thomas Goetz, DVM, chief of equine medicine and surgery at the University of Illinois College of Veterinary Medicine in Urbana, "spring grass has a very high carbohydrate content," which spells trouble for some horses that cannot adapt to the change in diet.

Equine veterinarians have known for years that some horses can handle the spring grass, while others will become ill and develop laminitis, a painful disease process in which the hoof wall separates from its attachments in the foot.

To figure out why some horses can't handle the lush grass, researchers at Virginia Tech conducted study and determined that there may be a genetic predisposition to what has been termed "pasture laminitis." The findings of this study suggested that the process occurring in horses that founder after eating spring grass was similar to a metabolic disorder in humans called Syndrome X. People affected by this disorder are likely to be diabetic, to have high blood pressure, and to be overweight. The disease is exacerbated by a diet high in carbohydrates.

And sure enough, the disease in horses is remarkably similar to that in humans. The researchers believe that this disorder, given the name Prelaminitic Syndrome, might be linked to a dominant gene, and might be associated with females. Horses that have the syndrome typically are overweight. Goetz explained that these animals "carry a lot more fat in the crest of their neck and tail head." Additionally, he mentioned that they usually have pockets of fat in other places as well.

The fat cells in these horses are suspected to produce inflammatory substances and other signals that interrupt normal glucose metabolism. Unfortunately, the typical look of Quarter Horses might have inadvertently caused horse breeders to select for animals that are insulin resistant and have this genetic predisposition.

According to the USDA, 54% of all laminitis cases in horses are from pasture laminitis. Now that a genetic predisposition and an actual disease causing the problem have been identified, there might be a potential in the future to test these horses for the gene.

Goetz recommends that owners who are concerned about their horse developing laminitis as a result of eating too much spring grass start off slow. He advises letting horses graze for 30 minutes a day, and then increase the time allotted over the course of a few weeks, as long as they handle the new diet well.

It's heartbreaking to prevent your horse from chowing down on delicious spring grass, but in the end they will thank you for preventing a painful foot ache.-Ashley Mitek, University of Illinois College of Veterinary Medicine

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