Any factor that increases the metabolic rate of an animal will increase the rate of oxidation and the level of free radical production inside body cells. Adequate Vitamin E must be available during these periods of increased metabolism to avoid cell damage.
The major factors that increase oxidation in greyhounds are:
Exercise - Physical exertion is the major contributor to free radical production in athletic animals such as greyhounds. With exercise, more oxygen is consumed to produce energy to fuel working muscles and greater levels of free radicals are produced. This increases their need for anti-oxidants such as Vitamin E to avoid tissue damage. If inadequate Vitamin E is available in muscle cell membranes muscle damage and degeneration can occur. This may be seen as reduced stamina, muscle weakness, poor racing performance and possibly muscle cramping. The heart muscle can also be affected and in severe cases of Vitamin E deficiency dogs have died from heart failure.
Pregnancy and growth - Pregnancy and growth both increase body metabolism and therefore increase free radical production. A deficiency of Vitamin E can lead to reduced sperm production in stud dogs, lowered fertility in bitches, low litter size and the birth of weak or dead pups.
Stress and Nervousness - Physical and emotional stress can increase the rate of body metabolism. Nervy animals often have a higher metabolic rate, and may require a higher dietary intake of Vitamin E, compared to their more placid kennel mates.
Injury, inflammation and infection - Tissue damage caused by injury or infection leads to increased free radical production. This can worsen or prolong the disease process and delay recovery. A Vitamin E deficiency has been shown to impair the immune system of dogs making them less able to respond to infections and to recover from injuries.
High fat diets - Diets high in polyunsaturated fatty acids (eg from vegetable oils) increase the level of lipid oxidation and free radical production in cell membranes. Extra Vitamin E is required as the fat content of the diet increases.