In non-human animals
In some regions (e.g. much of the northeastern and northwestern US and adjacent Canada, and the southeastern US), selenium deficiency in some animal species is common unless supplementation is carried out. Selenium deficiency is responsible (either alone or together with vitamin E deficiency) for many of the cases of WMD ("white muscle disease"), evidenced at slaughter or during necropsy by whitish appearance of striated muscle tissue due to bleaching by peroxides and hydroperoxides. Although this degenerative disease can occur in foals, pigs and other animal species, ruminants are particularly susceptible. In general, absorption of dietary selenium is lower in ruminants than in non-ruminants, and is lower from forages than from grain. Sheep are more susceptible than cattle to WMD, and goats are more susceptible than sheep. Because of seleniums role in certain peroxidases (converting hydroperoxides to alcohols) and because of the antioxidant role of vitamin E (preventing hydroperoxide formation), a low level of Se can be somewhat (but not wholly) compensated by a high level of vitamin E.  (In the animal, localization of peroxidases and vitamin E differs, partly because of the fat-solubility of vitamin E.)   Some studies have indicated that about 0.12 or 0.23 mg Se per kg of dry matter intake may be sufficient for avoiding Se deficiency in sheep in some circumstances. However, somewhat higher Se intake may be required for avoidance of  WMD where certain legumes are consumed.
The cyanogenic glycosides in some white clover (Trifolium repens) varieties may influence the Se requirement, presumably because of cyanide from the aglycone released by glucosidase activity in the rumen and inactivation of glutathione peroxidases by the effect of absorbed cyanide on the glutathione moiety.In areas where selenium deficiency in livestock is a concern, selenium (as selenite) may be supplemented in feed. In  some countries, e.g. the US and Canada, such supplementation is regulated. Neonate ruminants at risk of WMD may be administered both Se and vitamin E by injection; some of the WMD myopathies respond only to Se, some only to vitamin E, and some to either. References


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