Dr. Su A Lee, a recent graduate from the Stein Monogastric Nutrition Lab, talks about how dietary crude protein concentration affects the standardized ileal digestibility (SID) of amino acids in feed ingredients, and demonstrates that AA SID can be determined in pigs fed diets below, at, or slightly above crude protein requirements without affecting the result. Adapted from a presentation at the 2020 ASAS Midwestern Section meeting, Omaha, NE, March 2-4.