Most of you with horses are probably familiar with the term tying up. Tying up is a very painful muscle condition in horses that has several different causes but the most common one is a condition called polysaccharide storage myopathy, or PSSM. The name is not important but the condition occurs because there is an excessive amount of glucose or sugar stored in muscle cells. Signs of tying up include muscle stiffness, cramping, muscle pain, muscles that are hard to the touch, lameness in which the horse does not want to even move, and even brown colored urine.

In the past, the only method of diagnosing this muscle disease was to surgically take a piece of muscle from the horse's back leg and send it to the lab for a muscle biopsy. Although this is still the only method of diagnosing all muscle diseases, a new test has been developed by the veterinarians at the University of Minnesota. This is a genetic test that requires only blood or hair samples. Obviously this is less expensive than surgery and you don't have to be concerned about wound healing. This genetic test relies on the discovery that a mutation in a gene is in cases of PSSM. Since this is a genetic disease, genetic testing can detect affected animals. Because this is a dominant gene, only one parent has to be affected to pass the condition on to their foals. Many different types of horses can be affected with PSSM and can be diagnosed using genetic testing including quarter horses and related breeds, draft horses, warm bloods, Tennessee walking horses, Morgans, and others. So if you have one of these breed horses that has had muscle problems in the past, ask your vet about this genetic test for tying up.