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Importance and necessity of selenium

The importance and necessity of selenium in animal feed

The importance and necessity of selenium in animal feed was proved in 1980's. 
This element is available in nature in two forms: organic and inorganic

 Inorganic selenium is available in Selenate , selenite , Slnayd and also metal

 form. In contrast, plants receive selenium from soil in selenyte or selenite form

 and synthesis seleno amino acids. So, selenium is a part of Methionine and

 cysteine amino acids which is replaced with sulfur. The most using form

 of selenium which widely used as animal food additive during past 20 years,

is inorganic forms of sodium selenite and sodium selenite(basically in selenite form)

and nowadays the experience of selenium in animal feeding gives us important

information to more understand this element biological role. Limitations of inorganic

selenium use is well understood , like toxicity, Interactions with other nutrients ,

low savings , its low efficiency in transport to milk and meat and low ability to

supply selenium in body. Subsequently, a large part of the consumed element is

excreted but the form of selenium which is attractive today is selenium yeast or organic

selenium which have been madeBy imitating nature which means selenium is replaced

sulfur in sulfuric amino acids structure. Advantages of organic selenium are as follows:

Organic selenium is absorbed from the absorption site of amino acids so, has no interactions

with other minerals and does not sediment and is completely absorbable and also stored

in the body. So by using inorganic selenium, enriched foods for human use like enriched eggs,

milk and meat can be produced. Selenium has an important role in immune system. This element

protects white blood cells from some toxic substances like oxidants and does not allow them

destroying WBCs, and since selenium is under sulfur in the periodic table, plants and micro

organism are able to use selenium instead of sulfur in sulfuric amino acids such as: methionine,

cystine, and cysteine and produce selenomethionine and selenocysteine. Among these compounds

only selenomethionine is absorbed high efficacy in animals digestive system. Unlike plants,

animals do not have the ability to use selenium in the structure of the amino acid methionine,

and only can insert inorganic selenium in structure of cysteine. Selenium is present in all

tissues and cells of the body and can absorb thorough the abomasum , small intestine

and partly large intestine. However, its main storage area is liver.