Even though they are both antioxidants, they have different sites of action. Vitamin E acts on the biomembranes while selenium-dependent glutathione peroxidase acts in the cytoplasm. Vitamin E tends to be most effective in preventing lipid peroxidation while selenium is more effective in preventing free radical production. The benefits of increasing vitamin E are doubtful if you are feeding the maximum allowable level of selenium. There is little data with the horse, but recent data with mice show that increasing zinc intakes in aged mice increased the activity of the thymus gland and enhanced the immune system.
Research is needed to determine if the same response occurs in aged mares.
Yes, recent Minnesota research with mice showed that perinatal brain development was affected by copper concentration in the mother diet. Mice born to copper deficient dams had permanent brain disorders even when fed adequate copper after birth. British researchers have shown that spreading one pound of salt per square foot, before covering the silo with plastic, nearly eliminated surface spoilage. A. Selenium requirement during pregnancy has been difficult to measure in farm animals. However, recent research with rats show that there is a considerable transfer to the fetus via the placenta.