17 research outputs found
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)