A REVIEW OF SELENIUM/VITAMIN E RESPONSIVE PROBLEMS IN LIVESTOCK: A CASE FOR SELENIUM AS A FEED ADDITIVE IN CANADA

Abstract

It has been amply demonstrated by scientific experimentation that selenium (Se) and vitamin E are essential micronutrients required for the good health of animals throughout their life cycle and for the attainment of high levels of production. In Canada there is widespread occurrence of Se/vitamin E responsive diseases in livestock, causing substantial financial losses to animal producers. As the Se and vitamin E contents of feed ingredients and their effective availabilities vary widely, a continuous supply of an active form of these micronutrients to farm animals is required. Published data suggest that for prepared swine and chicken diets there is a need for supplementation with at least 0.1 ppm Se (from sodium selenate or selenite) and 10 ppm α-tocopheryl acetate. Turkeys appear to require dietary additions of 0.2 ppm Se and 10 ppm vitamin E. For beef cattle and sheep, either on the range or in confinement, "selenized" salt, mineral mixes, or mineral blocks appear at this time to be the preferred method for providing additional Se. Presently available data indicate that 26 ppm Se is an effective level in salt mixes for prevention of muscular dystrophy. It was estimated from recent published data on the Se content of Canadian food items that the provision of Se supplements to livestock, as described, would have a negligible influence on the average daily intake of Se by the Canadian public, thereby precluding controversy over any beneficial or detrimental role of the element in humans. The amount of Se that would be recycled through the animal excreta–soil–plant–human food chain was exceedingly small.