Can methionine concentration in plasma be related to milk protein?

Methionine (Met) is, in most dairy rations, the first limiting amino acid for milk and milk protein production. The blood concentration of this amino acid is often used as a proxy for its bioavailability, assuming that changes in concentration are directly related to dietary variations. However, since blood is a transport organ, concentrations of amino acids in blood do not only reflect the dietary supply, but also the amount used by the organs. Although in some studies blood amino acids have