Selenium ngộ độc là một căn bệnh cổ xưa và được tài liệu (Rosenfeld và Beath 1964). Các dấu hiệu của nó đã được báo cáo trong số các vật nuôi trong nước bởi Marco Polo ở miền tây Trung Quốc gần biên giới Turkestan và Tây Tạng trong các năm khoảng 1295, trong chăn nuôi, gà, và trẻ em trong Colombia, Nam Mỹ, Cha Pedro Simon năm 1560, ở người lớn của con người trong Irapuato Mexico, trong khoảng 1764, và giữa các con ngựa của Kỵ binh Hoa Kỳ ở Nam Dakota năm 1857 và một lần nữa vào năm 1893 (Rosenfeld và. | CHAPTER 31 Selenium INTRODUCTION Selenium poisoning is an ancient and well-documented disease Rosenfeld and Beath 1964 . Signs of it were reported among domestic livestock by Marco Polo in western China near the borders of Turkestan and Tibet in about the year 1295 among livestock chickens and children in Colombia South America by Father Pedro Simon in 1560 among human adults in Irapuato Mexico in about 1764 and among horses of the . Cavalry in South Dakota in 1857 and again in 1893 Rosenfeld and Beath 1964 . In 1907 08 more than 15 000 sheep died in a region north of Medicine Bow Wyoming after grazing on seleniferous plants. The incidents have continued and recent technical literature abounds with isolated examples of selenosis among domestic animals and wildlife. Selenium Se was first identified as an element in 1817 by the Swedish chemist Berzelius. It is now firmly established that selenium is beneficial or essential in amounts from trace to pg kg ppb concentrations for humans and some plants and animals but toxic at some concentrations present in the environment Rosenfeld and Beath 1964 . Selenium deficiency was reported among cattle grazing in the Florida Everglades which showed evidence of anemia slow growth and reduced fertility Morris et al. 1984 . Selenium deficiency has been demonstrated in Atlantic salmon Salmo salar Lorentzen et al. 1994 in various species of deer in Florida and Washington Hein et al. 1994 McDowell et al. 1995 and in free-ranging ungulates in Washington state including moose Alces alces and bighorn sheep Ovis canadensis Hein et al. 1994 . Conversely calves of Indian buffaloes died of selenium poisoning after eating rice husks grown in naturally seleniferous soils Prasad et al. 1982 . Adverse effects of excess selenium are reported on reproduction of cattle monkeys sheep swine rats and hamsters including fetal and maternal death and a dramatic increase in developmental abnormalities Domingo 1994 . Severe reproductive and .
