Both genetic and nutritional factors are recognized as potential contributors to developmental orthopedic disease (DOD) in growing horses. New information points to a possible link between the two factors. The genetic factor could involve a glucose intolerance or insulin insensitivity which is expressed when young horses are fed large amounts of carbohydrates to promote rapid growth.

Sarah Ralston, D.V.M., Ph.D., is a faculty member in Animal Science at Rutgers University and the chairperson of the American College of Veterinary Nutrition. She has been researching glucose and insulin metabolism in horses for over 20 years. At the 1999 Kentucky Equine Research Conference for Feed Manufacturers, Dr. Ralston reported that some horses under one year of age which develop DOD, such as osteochondritis dissecans (OCD), also exhibit glucose intolerance. When these horses are fed large amounts of grain, their glucose concentrations can be maintained near normal only by producing excessive amounts of insulin. Increased insulin can affect bone metabolism by preventing the proper formation of bone from cartilage, possibly resulting in OCD lesions. This condition should be suspected whenever familial groups of horses have developed DOD. Management of these horses would involve greatly decreasing their starch intake by substituting fat and high-quality forages for grains as nutrient sources.

Fat in horse rations does not produce the typical glycemic response (150% increase in plasma glucose and corresponding plasma insulin increase for two to three hours following meals) seen in horses fed high-grain rations. By using fat in the form of stabilized rice bran in JUNIORGLO™ and in a FORAGE FIRSTâ program, growth can be maintained without excessive carbohydrates from grains and the resulting excessive insulin production.

As always, total rations for young horses must be balanced for energy, protein, calcium, phosphorus, copper, and zinc to minimize the occurrences of DOD. GROSTRONGâ Minerals for Horses are available in two formulations to complement grass hays and legume (alfalfa, clover) hays. GROSTRONG Minerals provide major and trace minerals and vitamins in proper amounts for growing horses and for mares during late gestation and lactation. Since several forms of DOD are associated with mineral deficiencies or imbalances in broodmares, dietary prevention of DOD should begin with proper broodmare nutrition. If DOD is suspected at your horse operation, consult an equine nutritionist and/or veterinarian for help managing the problem and preventing further occurrences.

 

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