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

Selenium in Crops in the United States in Relation to Selenium-Responsive Diseases of Animals

Selenium-responsive diseases of livestock occur frequently in the United States and have been responsible for serious economic losses. White muscle disease (WMD) of lambs and calves is perhaps the most common of these disorders. The occurrence of WMD is related to the geologic nature of the soil parent material (19). There is also evidence that regional patterns of occurrence of WMD are related to regional differences in the Se concentration of feed crops (3). In the U. S., there are also areas where Se toxicity has been evident in livestock. These areas have been studied extensively, and the distribution of geologic formations that form soils capable of producing high-Se plants has been established (14, 17, 21). This report presents a map of the U. S. showing areas where the Se content of plants is adequate to protect animals from WMD, and areas where low levels of Se in plants may lead to Se-responsive diseases in animals, and describes how it was prepared. A similar survey of plant Se levels has been reported from western Australia (9)

Selenium in Crops in the United States in Relation to Selenium-Responsive Diseases of Animals

Selenium-responsive diseases of livestock occur frequently in the United States and have been responsible for serious economic losses. White muscle disease (WMD) of lambs and calves is perhaps the most common of these disorders. The occurrence of WMD is related to the geologic nature of the soil parent material (19). There is also evidence that regional patterns of occurrence of WMD are related to regional differences in the Se concentration of feed crops (3). In the U. S., there are also areas where Se toxicity has been evident in livestock. These areas have been studied extensively, and the distribution of geologic formations that form soils capable of producing high-Se plants has been established (14, 17, 21). This report presents a map of the U. S. showing areas where the Se content of plants is adequate to protect animals from WMD, and areas where low levels of Se in plants may lead to Se-responsive diseases in animals, and describes how it was prepared. A similar survey of plant Se levels has been reported from western Australia (9)