The defect in metabolism, believed to be present in up to 50 percent of draft horses and a lesser percentage of Warmbloods
and draft-related crosses, can cause a number of clinical problems. Affected horses may be stiff with mild to severe gait
abnormalities. They might show difficulty cantering with an odd hind-limb motion. Some affected horses will be poorly muscled
despite exercise or even show muscle wasting. Farriers often comment that these horses become difficult to shoe because they
have problems holding up their hind feet. Tying up (exertional rhabdomyolysis) or signs consistent with muscle spasms are
also seen. It is important to note that many of these signs, in their more subtle forms, are also seen in young, slowly developing
but normal Warmbloods that lack adequate muscle and balance for their large frames. Differentiating between actual disease
and developmental weakness can be a challenge for the practitioner.
Diagnosis of EPSM is by muscle biopsy, and because this disease can closely resemble other developmental issues, accurate
diagnosis is to be encouraged. Treatment is a special diet high in fat. Valentine recommends a diet where 20 to 25 percent
of the total digestible calories are derived from a fat source. Adding corn oil to the feed ration is one way to provide this
diet, and there are many newer commercially prepared and balanced feeds that can be used for EPSM.
In a 2001 American Veterinary Medical Association study of 250 horses diagnosed with EPSM more than 88 percent of all horses
showed significant improvement with a high-fat diet alone. Though the percentages of EPSM cases are higher for drafts than
for Warmbloods, these breeds share some similar genetics, and this disease should be of concern for Warmblood owners and their
veterinarians. Reducing the carbohydrate exposure for Warmbloods, already a good idea because of OCD concerns, is also of
importance because of muscle function as well.
"Warmblood owners should avoid the temptation to feed all their horses a high-fat diet though because those Warmbloods not
affected by EPSM will then be more at risk of becoming overweight with all of those potential complications," Adams cautions.
The search for the exact problem with carbohydrate metabolism in these horses is progressing, and there is speculation that
differences in Warmblood response to insulin may be involved.
Reproduction in Warmbloods also can present the equine practitioner with some slightly unique challenges. Because much of
the Warmblood breeding in this country is done with cooled or frozen semen, it is important for practitioners to have a good
working knowledge of equine viral arteritis (EVA). EVA is a viral infection that affects horses and is particularly important
because certain strains can cause abortions in susceptible mares, and a high percentage of stallions become carriers. Some
breeds carry more EVA risk than others.
EVA "may occur in only 1 to 3 percent of the population in Arabians and Thoroughbreds, whereas it had reached 70 to 80 percent
in Standardbreds," says Dr. Peter Timoney, a leading expert on EVA at the University of Kentucky Gluck Research Center.
There are a fairly significant number of Warmblood stallions that are EVA positive.
"Current estimates put the number at over 50 percent," Timoney says, and this can have economic implications for Warmblood
breeding operations that may experience outbreaks of abortions and/or neonatal deaths. EVA abortions generally occur one to
three weeks after exposure to the virus, and the mares may show no other signs of disease. The stage of pregnancy does not
appear to influence the outcome as both early and late abortions can occur. Adding to the confusion, some severely affected
mares do not abort. Most horses with EVA show signs of ataxia, fever, swelling of the limbs, anorexia, nasal discharge and
skin rash around the head and neck. The majority of these horses tend to make uneventful recoveries and clearly, more remains
to be learned about this disease.
EVA-positive semen serves as one means of spread of this disease, especially among Warmbloods, so veterinarians should be
aware of the suggested methods for managing this problem. "Vaccination is the first line of defense against this disease,"
Timoney says. "All stallions should be vaccinated, and infected carrier stallions identified."
He also strongly recommends vaccinating young colts so that these horses do not get the chance to become infected and develop
into carriers. Infected horses should be bred only to vaccinated mares. "Owners seem to have developed a 'mental hangover'
concerning this disease," he adds, and many breeders cite problems with exporting vaccinated horses and the threat of lost
sales or the inability to compete internationally as a major block to vaccination acceptance. But he refutes the claim.