Targeted Diets Can Aid Horses With Liver Disease

By
BRYAN M. WALDRIDGE

THE power of targeted equine nutrition programs is unquestionable. Take, for instance, the feeding management practices that almost entirely relieve horses of the crippling signs associated with tying-up. By reducing starch intake and filling the caloric void with fat and fi ber,many racehorses that are genetically predisposed to the disease have become successful athletes. This demonstrates the benefi ts of dietary manipulation.

Even more precisely targeted diets can benefi t horses with certain compromised organs, such as horses with liver disease. The liver accounts for approximately 1% of an adult horse’s bodyweight. The organ lies almost entirely to the right of the median and is completely encased by the rib cage.

Of greatest signifi cance anatomically is that a horse has no gall bladder. Because of this, bile is emptied directly from the liver into the duodenum. Horses are continuous grazers and constantly secrete bile (unlike humans and other animals with gall bladders that store and release bile when a meal is eaten).

The liver plays a crucial role in digestive processes and is chiefly involved in regulating nutrient distribution.

Nutrients absorbed in the gastrointestinal tract must pass through the liver via portal circulation. Serving as a  clearinghouse of sorts, the liver assigns nutrients to essential roles. Some are metabolized for energy, some are transformed to other nutrient classes,

some are sent to peripheral tissues and others are stored by the liver for future use.

Another key function of the liver is maintaining consistent blood levels of nutrients between feedings.

While the liver is resistant to damage and can usually function with as little as two-thirds of its normal mass, wholeorgan disease is possible and is life threatening when it occurs.

The Kentucky Livestock Disease Diagnostic Laboratory reported that hepatitis (infl ammation with varying degrees of degeneration of the liver) was the most commonly diagnosed liver problem, with 6-10 cases per year.

Liver disease in mature horses is most often caused by exposure to toxic plants or feed toxins, infection or bile stones. Horses can occasionally develop serious liver disease after treatment with products made from horse blood, such as plasma or tetanus antitoxin.

Miniature horses, ponies and donkeys that stop eating, usually due to serious illness, can develop a potentially fatal accumulation of fat in the liver. Blood work will usually reveal elevations in liver enzyme activity, i.e., gamma-glutamyl transferase, aspartate aminotransferase, lactate dehydrogenase and serum alkaline phosphatase.

Measurement of serum bile acids is a useful blood test that evaluates liver function. Because the liver produces many of the proteins in blood, horses with liver disease may have low blood protein concentrations, especially albumin. Bilirubin can also be elevated, but another important and common cause of elevated bilirubin is anorexia.

Biopsy is the most defi nitive diagnostic test for horses suspected of having liver disease. Liver biopsies are generally safe, and veterinarians can perform them in standing horses with ultrasound guidance. Liver biopsy, bacterial culture and microscopic examination can usually determine the cause of liver disease, as well as the prognosis.