Pick up your newspaper, farm paper or farm magazine and glance at the feed ads. Chances are that one or more of them will mention "essential amino acids," and most of the rest will have something to say about protein supplement or feed efficiency. While feeders and feed manufacturers may think and talk in terms of "feed efficiency" when they talk about protein feeds, their principal problem is that of making up deficiences of essential amino acids.
Fox, Sidney W.
"The Amino Acid Story,"
Iowa Farm Science: Vol. 8
, Article 4.
Available at: https://lib.dr.iastate.edu/farmscience/vol8/iss7/4