X_and_Z
Songster
Just because a amino acid is in a feed ingredient/s doesn't meen that it can be used, or all of it can be used.
Example being, Soybean meal (48%) protein has .64% Methionine which 91% of Methionine is digestable by chickens so your bird is really getting .58% Methionine and not .64.
I completely agree and the issue is not just specific to protein. Take the egg - raw egg white has a biotin inhibitor that is mostly, but not completely destroyed when the white is cooked. The yolk has a large amount of biotin that is supposed to more than offset the biotin inhibitor in the white. However many people like feeding raw egg whites (the yolks contain almost all the fat in an egg) and are not aware of the biotin inhibitor.