University of Kentucky College of Agriculture

AA Limiting Order Version 1.0

AA Limiting Order Version 1.0 is a spreadsheet for identifying the limiting amino acids in various combinations of feed ingredients for swine



To use the program, click on the the following link:

For information on using the program, and a link to manual, click the following link:


Gary L. Cromwell and Beob G. Kim
University of Kentucky, Lexington, KY


One of the most effective methods of reducing N excretion by pigs is to reduce the dietary protein level and supplement with amino acids (AA). However, effective AA supplementation requires knowledge of the order in which AA become limiting as dietary protein is reduced in diets containing various combinations of feed ingredients, as well as knowledge of the relative magnitude of difference between the AA in their limitation order. This information is fairly well known for grain-soy diets, but is less well known for diets containing various combinations of feedstuffs. A user-friendly Microsoft Excel program was designed to address this issue for pigs at all stages of growth and for gestating and lactating sows. The program allows users to include numerous feedstuffs that contribute AA to the diet and graphically illustrates the order that AA become limiting as the dietary level of the major protein source(s) decreases. The program converts the dietary concentrations of AA to a percentage of the pig? requirement, then regresses those percentages on the inclusion level of the major protein sources in the diet. As the protein source decreases from a level that meets >100% of the pig? AA requirements to a level of zero, the regression line for each AA intersects a horizontal line, which is set as 100% of the requirement for each AA. Proceeding along the horizontal line, one can readily assess the order and spacing between the AA as they become limiting. The program is applicable for AA on a total, apparent digestible, or true digestible basis. An economic component also is included. The validity of the output is dependent upon the accuracy of the AA requirements and the accuracy of the AA analysis of the feedstuffs. Information generated from this program allows nutritionists to identify potentially limiting AA in different feedstuff or growth stage scenarios. It will also help to more precisely determine the amount of intact protein that can be replaced with AA to minimize N excretion when various combinations of feedstuffs are fed to pigs.