Selenium Deficiency in Cattle
Selenium (Se) is an essential trace mineral for cattle and humans alike. It is essential because it a component of several enzymes that are important antioxidants. It is a trace mineral because it is needed in very small (trace) amounts. We usually talk about Se requirements in terms of tenths of parts per million (ppm)—remembering a part per million is 1 inch in 15.8 miles—we are talking about a tenth of an inch in 15.8 miles. Selenium deficiency is common in many parts of the United States—such as the northwest, Great Lakes region, the west coast, intermountain west, eastern seaboard, and the southeastern U.S. As we have become better farmers the amount of Se in the feeds and hays has decreased markedly. Areas that used to be adequate or marginal in terms of forage Se have now been recognized as being deficient. The reason for this is that plants do not require Se, it is not necessary for plant growth or plant health. To plants Se looks just like sulphur (S) and thus with low Se in soils it is not absorbed into the plant roots. So our good agronomic practices like irrigation, higher production cultivars, legume production (higher in S than grasses), fertilization (particularly sulphate fertilizers), and intensive grazing all decrease the concentration of Se in feeds. Additionally, our cattle have been selected to grow faster and mature quicker so their requirements for Se and other nutrients have increased. Bottom line: we are seeing more Se deficiency problems in beef cattle than in previous decades.
Maas, John. “Selenium Deficiency in Cattle.” National Cattleman’s Beef Association. 2007. Web 17 Apr 2011.