NUTRITION
PIH-5
pork industry handbook
PURDUE UNIVERSITY - COOPERATIVE EXTENSION SERVICE - WEST LAFAYETTE, INDIANA
Protein and Amino Acids for Swine
Authors
T. D. Tanksley, Jr., Texas A&M University
D.	H. Baker, University of Illinois
A.	J. Lewis, University of Nebraska
Reviewers
G. L. Allee, Kansas State University
W. F. Gipp, Montana State University
P. J. Holden, Iowa State University
In the U.S., the most challenging task in formulating swine diets is to provide the protein and amino acids needed for maximum lean growth and reproductive performance at the least cost. To formulate diets effectively, one must know: 1. The amino acid requirements of the different classes of pigs, and 2. The composition of the various feedstuffs and their ability to supply specific amino acids. The “competitive edge” goes to the person who can mesh these together in diets and a feeding program to produce lean pork at the most economical cost.

The fact sheet will consider both amino acid requirements and the ability of various feedstuffs to supply the amino acids, but first let’s review some basic concepts of protein and amino acid nutrition.

Protein vs. Amino Acids
The use of percent of crude protein to indicate the ability of a mixed feed with unknown ingredients to meet the amino acids needs of a pig’s diet is out-dated and of little value. The content of essential amino acids gives a much better indication of nutritional quality than percent crude protein. This is because feed proteins differ widely in percentage of specific amino acids that they contain.

Muscle protein (lean tissue) is composed of about 20 different amino acids. Ten of these must be supplied in the pig’s diet; the other amino acids can be synthesized in the body rapidly enough for maximum growth if a source of dietary nitrogen and adequate energy are present. The 10 that must be supplied in the diet are called essential amino acids; the others are classified as nonessential. The 10 essential amino acids are: lysine, tryptophan, threonine, methionine, isoleucine, valine, leucine, histidine, arginine, and phenylalanine.

Actually, swine do not have a protein requirement per se, but rather they have a dietary requirement for:
1.	Specific amounts of the essential amino acids, and
2.	Nonspecific nitrogen to synthesize the non-essential amino acids.
Any diet formulated from natural feedstuffs that satisfies the first requirement will automatically satisfy the need for nonspecific nitrogen.

The fallacy of using percent crude protein of a mixed feed with unknown ingredients as an indicator of amino acid quality is shown in Figure 1. Figure 1 shows the ability of a 16% protein corn-soybean meal diet, a 16% protein corn-meat and bone meal diet and a 16% protein corn-peanut meal diet to meet the growing pig’s (40 to 80 lb.) requirement for lysine, tryptophan and threonine (the three most limiting amino acids in U.S. diets). The solid portions of the bars in Figure 1 show the contribution of corn in meeting the requirements for lysine (27%), tryptophan (33%), and threonine (49%). The diagonally lined portions in Figure 1 show the contribution of soybean meal, meat and bone meal and peanut meal, respectively, toward meeting the lysine, tryptophan, and threonine needs of the growing pig. Only the corn-soybean meal diet meets the requirements for all three amino acids to support maximum growth. The corn-meat and bone meal diet is very deficient in tryptophan and barely adequate in lysine. The corn-peanut meal diet is inadequate in both lysine and tryptophan and barely adequate in threonine. This indicates clearly that the crude-protein content of a mixed feed is an unreliable indicator of amino acid quality of the feed unless one knows the feedstuffs used in preparing the feed. If a crude-protein content of 9% is used for corn and sorghum in formulating diets, the crude-protein content of a corn-soybean meal or sorghum-soybean meal diet is very meaningful and is a reliable indicator of their ability to meet the amino acid needs of a pig at a specific weight. However, when other high protein feedstuffs are used instead of soybean meal, the crude-protein value is less meaningful.

Other Concepts of Amino-Acid Nutrition
1.	Protein synthesis is an “all or nothing” process. If any one of the essential amino acids needed to syn-

Cooperative Extension work in Agriculture and Home Economics, State of Indiana, Purdue University and U. S. Department of Agriculture Cooperating. H. A. Wadsworth, Director, West Lafayette, IN. Issued in furtherance of the acts of May 8 and June 30, 1914. The Purdue University Cooperative Extension Service is an affirmative action/equal opportunity institution.