The method consists in hydrolysing with hydrochloric acid of a ground test portion, dollowed by separation of the total lysine by column chromatography and determination by spectrometry at 570 nm. Reaction of a second ground test portion with an ethanolic solution of 2,4-dinitrofluorobenzene in an alkaline medium, purification, then hydrolysis with hydrochloric acid, separation of the non-available lysine by column chromatography, and determination by spectrometry at 570 nm.