Selenium Content of Forage and Hay Crops in the Pacific Northwest

A map illustrating the Se content of forage and hay crops in different sections of the Pacific Northwest was prepared, based on analyses of crop samples. The primary criterion used in mapping was to delineate areas where forage and hay crops generally contain insufficient Se to meet requirements of lambs and calves, and thus prevent white muscle disease (WMD) and other Se-responsive diseases. The minimal requirement may vary from 0.03 to 0.10 ppm Se in the diet, depending upon the diet level of vitamin E and possibly other substances. Under normal livestock management practices, WMD is common when forages and hay contain less than 0.10 ppm Se and the incidence is greater at lower Se levels. The western half of Washington and Oregon and part of northern California comprise an extremely low Se area. The eastern half of Washington, northern Idaho, extreme western Montana, and the northeast corner of Oregon comprise a low Se area. Most of the remaining portion of the Northwest may be considered as variable in Se, with farm-to-farm variations common, but some small areas of adequate Se were found and mapped