Which of the following is a protein source used in feedstuffs?

• A. Animal or plant proteins, legume seeds, or non-protein nitrogen (NPN).
• B. Pure water.
• C. Salt.
• D. Silica sand.

Answer: (A)

Protein in feeds comes from true proteins found in animal or plant sources, including the proteins in legume seeds, which provide amino acids for growth and production. In ruminant nutrition, non-protein nitrogen is also used because rumen microbes can convert it into microbial protein, effectively boosting the animal’s protein supply even though the source isn’t a peptide. So these items together are considered protein sources in feedstuffs. Pure water, salt, and silica sand do not supply usable protein or nitrogen for producing protein, so they aren’t protein sources in feeds.