No problem.
Crude protein is made up of amino acids. Lysine, methionine are amino acids.
Essential amino acids cannot be made by the body so therefor must come from food. Different species of animals are able to use some amino acids (essential) to make up the rest of the amino acids (non-essential).
One thing to consider is that to make non-essential amino acids, the body must use up some of the essential ones, possibly rendering them deficient.
In humans there are 9 amino acids that must be provided in the diet.
In chickens, there are 13 essential amino acids including threonine and tryptophan in addition to the aforementioned.
Grains and legumes complement one another in providing amino acids but not completely. To make a complete feed, feed companies either add some animal protein or more commonly, synthetic lysine, methionine and possibly other essential amino acids depending on the analysis of the feedstuffs entering the manufacturing process.
http://www.ag.auburn.edu/~chibale/an12poultryfeeding.pdf
http://www.themodernhomestead.us/article/Feeding+from+Home+Resources.html
http://babel.hathitrust.org/cgi/pt?id=coo.31924003011545;view=1up;seq=15
http://ps.oxfordjournals.org/content/58/2/376.full.pdf
This subject isn't a one size fits all. For instance, many backyard keepers in the cities around me are, by statute, limited to 4 or 6 birds regardless of their means to care for them. They may be on 3 acre lots or postage stamp size yards.
I usually keep from 25 too 100 birds depending on the time of year. They pasture in rotating paddocks but that space isn't limitless in its ability to provide sustenance.
If one has 4 chickens in a small backyard consisting of well manicured monoculture grasses, they're kidding themselves if they believe their birds can glean much from that.
If one has a larger flock on perhaps 10 acres of a mix of pasture, woodland and brush, the birds may be able to get more of what they need - but, that depends on where they're located. If they're in Mississippi or Oregon, they may be able to do so for more of the year rather than those in Minnesota, Maine or So. California (drought).
If one has a free ranging flock in Nicaragua, their management and feeding is dramatically different than those in Alaska or Ethiopia.