Thirteen mineral elements are essential to animals, and must be present in their diet: calcium, chlorine, cobalt, copper, iodine, iron, magnesium, manganese, phosphorus, potassium, sodium, sulfur, and zinc. Under certain conditions or in certain limited areas, livestock production has been greatly improved by addition of one or more of these essential elements to the animals' diet. This finding has led to the extensive use of mineral supplements in livestock feeding even in areas where specific deficiencies have never been shown to exist. It is important that livestockmen know definitely the conditions and areas under which one or more minerals is likely to be lacking so that expenditures for unnecessary feed supplements for specific situations can be avoided.

The above progress report is based on Research Project No. 1569.