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