by Greg Reinhart, PhD (Research & Development, The Iams Company), Ken Hinchcliff BVSc, MS, PhD (Veterinary Clinical Services, Ohio State University), Arleigh Reynolds, DVM, PhD (Cornell University Research & Development, New York State College of Veterinary Medicine), Mike Hayek, PhD (Research & Development, The Iams Company)
Vitamin E is a fat soluble vitamin that works with other antioxidants in the body to prevent oxidative damage. If vitamin E is present at appropriate levels, it helps maintain defense against disease and environmental insults. A deficiency of vitamin E results in damage to red blood cells, muscle, nerve cells and other cells in the body. Unfortunately, there is a great deal of myth and misinformation about vitamin E. Both mushers and scientific people are exposed to extreme points of view.
Low vitamin E status has been previously speculated to be a risk factor in sled dogs developing exertional rhabdomyolysis (“tying-up syndrome”). the focus on vitamin E escalated when pathologists determined that three of the dead dogs from Iditarod ’97 had significant muscle degeneration. Each of these dogs had vitamin E tissue concentrations that were lower than those of the two which died of conditions unaccompanied by muscle pathology. Although this information does not establish that decreased vitamin E levels are the cause of potential fatal myopathies, it would suggest the need for appropriate precautionary steps.
Current recommended dietary allowances for vitamin E in dogs is 20 IU per kilogram of a typical diet.(1)
This recommendation is based on studies in non-exercising dogs consuming a normal diet (20-30% of calories from fat). This recommendation level of vitamin E may not be enough for the sled dog. Sled dogs are exposed to strenuous exercise that causes the body to use up vitamin E at a faster rate. Most premium dog foods contain many times the recommended 20 IU of vitamin E per kilogram of diet. However, most commercially available dry foods are supplemented with fresh meat and fats prior to feeding and this dilutes the vitamin E that comes in the commercially prepared dog food. The practice of adding vegetable and fish oils, which contain polyunsaturated fatty acids, to these commercially prepared dog foods also results in dietary vitamin E being used up at a faster rate. Vitamin E is used by the body to keep theses polyunsaturated fatty acids from becoming rancid. This is not a problem as long as the total diet (dry food, fresh meats and added fats) has adequate vitamin E. Based on all of these factors, additional vitamin E supplementation to sled dogs is worth consideration.
Vitamin E supplement must be approached in a prudent manner and extremes avoided. Vitamin E is absorbed into the body by the same route as the other fat soluble vitamins (vitamins A, D and K). It is possible that excessively high levels of vitamin E could compete with the other fat soluble vitamins resulting in lower absorption of these necessary nutrients. For example, excessively high levels of vitamin E intake in normal dogs resulted in bleeding disorders due to an induced vitamin K deficiency (too much vitamin E “squeezed out” the vitamin K and prevented it from being absorbed at the amounts required for normal blood clotting.) Excessive levels of vitamin E have also been associated with nausea.
The source of the vitamin E used for supplementation is also very important. There are many forms of vitamin E. the preferred type (most biologically active form) is know as alpha-tocopherol. It is recommended that alpha-tocopherol, alpha-tocopherol acetate, or alpha-tocopherol succinate be used. Other forms of vitamin E (gamma-tocopherol, beta-tocopherol) do not provide the same level of protection within the body that alpha-tocopherol does. Avoid cheap vitamin E supplements that contain high levels of vitamin A. Providing this type of vitamin supplement to dogs on a long term basis could lead to an overdose of vitamin A and possibly lead to vitamin A toxicity.
Recommendation for Sled Dogs:
We recommend that each exercising sled dog be supplemented with 400 IU per day over what they are currently receiving in their normal diet. This vitamin E should be in the form of alpha-tocopherol. Human vitamin E supplements in the form of alpha-tocopherol are commercially available in 400 IU capsules and these can be given to dogs. There are no known contraindications to recommending this level of additional vitamin E supplementation.
(1) National Research Council (U.S.) 1985. Subcommittee on Dog Nutrition. Nutrient requirements of dogs. © 1997
BASED ON DATA OBTAINED DURING THE 1997 IDITAROD