Although not strictly interchangeable, selenium and vitamin E go hand in hand and play a vital role in enhancing fertility and reducing mastitis, with vit E in particular seeming to reduce cell counts in fresh-calved cows. Vet John Shaw takes us through the scientific evidence. Selenium was discovered in 1818 and was initially thought to be toxic as two important diseases found in the Great Plains of America (alkali disease and blind staggers) are the result of chronic selenium poisoning. But in the late 1950s it was found to be an essential micro-nutrient and subsequently shown to have important roles in growth, fertility and immunity of cattle. Vitamin E is one of the fat-soluble vitamins (A, D, E and K) and is actually a group of compounds, themost common and active of which is alpha-tocopherol. Vitamin E is found in large quantities in fresh forages but levels decrease rapidly after conservation. Fresh green forage contains five or six times more vitamin E than stored feeds and vitamin E levels in cows' blood generally fall in the winter, although some vitamin E can be stored in the liver.
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