The proteins in milk are mainly casein, albumin, globulin and lactin, etc. The 20 kinds of amino acids contained in the 8 kinds of amino acids are essential to the human body, and the proteins in milk are full-value proteins, and its digestibility is as high as 98%. The fat in milk is high quality fat, the best quality, its digestibility is more than 95%, and contains a lot of fat-soluble vitamins. The lactose in milk is galactose and lactose, which are the most easily digested and absorbed sugars. Milk minerals and trace elements are dissolved state, and the proportion of the content of various minerals, especially calcium, phosphorus ratio is more appropriate, it is easy to digest and absorb.