Alkali disease

Alkali disease is a toxicity condition in animals caused by the excessive incorporation of selenium, specifically the amino acid analogue selenomethionine, into body tissues. Because selenium closely resembles sulfur chemically, it is taken up readily in place of the amino acid methionine during protein synthesis, and its buildup in structural proteins and keratin disrupts their normal function. Documented in cattle, birds, and fish exposed to high dietary selenium, most often from grazing on seleniferous soils and plants, the condition is characterized by emaciation, loss of hair or feathers, deformation and shedding of hooves, general loss of vitality, and erosion at the joints of the long bones. Bacteria tolerate much higher rates of selenium substitution than vertebrate animals, which is why livestock and wildlife in seleniferous regions suffer significant pathological effects that are not seen in simpler organisms exposed to the same soil chemistry.