WHAT IS THE DIFFERENCE BETWEEN EPSM AND “MONDAY MORNING DISEASE”?
“Monday Morning Disease” is the disease most often described in hard-working draft horses that are given a day off with full grain feed. When they are asked to work the next day, these horses show severe signs of what is often called “tying up” in saddle horses, in which muscles become stiff, begin to degenerate, and the horse will stop moving and may even go down. Massive muscle injury results in release of the pigment myoglobin from damaged muscle, and the urine becomes a dark red-brown (myoglobinuria). Because of this urine color, the disease has also been called “azoturia”. Other names include “set fast” and “exertional myopathy” or “exertional rhabdomyolysis”. It is thought that the the massive muscle damage that occurs in EPSM drafts occurs due to the lack of muscle energy. The common finding of slightly increased levels of muscle enzymes in the blood in apparently normal, or only mildly affected EPSM horses suggests that these horses often have low-level muscle injury during exe
