NUTRITION
PIH-5
pork industry handbook
COOPERATIVE EXTENSION SERVICE • PURDUE UNIVERSITY • WEST LAFAYETTE, INDIANA
Protein and Amino Acids for Swine
Authors
T. D. Tanksley, Jr., Texas A&M University
D. H. Baker, University of Illinois
Reviewers
John Landers, Oregon State University
Gary L. Allee, Kansas State University
No pig can develop lean tissue (muscle) to its genetic potential nor can a sow realize her maximum reproductive potential unless their diets contain sufficient protein with the correct amino acid composition. Protein is made up of many sub-units called amino acids. During the digestive process, proteins are broken down into individual amino acids. The animal absorbs amino acids from the intestines and recombines them within the body tissue into new protein molecules. Each of the body proteins are synthesized by the amino acids joining together in a pre-established sequence dictated by the genetic background of the animal.

Muscle protein is composed of about 22 different amino acids. Ten of these amino acids must be supplied in the pig’s diet; the others 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 non-essential. The 10 essential amino acids required by swine include: arginine, histidine, isoleucine, leucine, lysine, methionine + cystine, phenylalanine + tyrosine, threonine, tryptophan and valine.

Actually, swine do not have a protein requirement per se, but rather they have a dietary requirement for:
1.	Non-specific nitrogen to synthesize the non-essential
amino acids.
2.	Specific amounts of the essential amino acids.
Any diet formulated from natural feedstuffs that
satisfies the second requirement will automatically satisfy the need for non-specific nitrogen. Even though the pig does not have a specific protein requirement, most ration formulators have attempted to meet the amino acid requirements simply by feeding prescribed protein levels. Most rations will meet this objective if high quality protein feeds are used with the cereal grains.

Protein synthesis is an “all or nothing” type of synthesis. If any one of the essential amino acids needed to form a protein is deficient, that protein cannot be formed. Nothing explains the concept of limiting amino acids better than the age-old illustration that likens a protein to a wooden barrel made up of rings and staves. The amino acids are the staves, and since a barrel will only hold water to the height of its lowest stave, a protein will only allow the pig to lay down meat to the extent of the amino acid present in the least amount. This amino acid, the shortest stave in the protein barrel, is called the first-limiting amino acid, the next in shortest supply, the second-limiting amino acid and so on. Therefore, quality of protein (presence and amount of the 10 essential amino acids) is more important than the total amount of protein fed.

Several principles of protein-amino acid nutrition are illustrated in the results of a 21 -day feeding trial conducted with young pigs averaging approximately 20 lb. initially. Two different high protein sources (soybean and peanut meal) plus supplemental lysine were used in the sorghum-based diets.
	Diet				Pig performance	
 No.	 Type of diet	Dietary lysine	Dietary protein	Daily gain	Daily feed intake	Gain/ feed
 1.	 Sorghum-soybean meal	 1.07	percent 20.2	 1.19	pound 2.28	 .52
2.	Sorghum-peanut meal	.54	20.2	.55	1.54	.36
3.	As 2 + lysine	1.07	20.2	.92	2.23	.41
4.	Sorghum-peanut meal	1.07	40.0	.68	1.55	.44
Cooperative Extension Work in Agriculture and Home Economics, State of Indiana, Purdue University and U. S. Department of Agriculture Cooperating. H. G. Diesslin, Director, West Lafayette, Ind. Issued in furtherance of the Acts of May 8 and June 30, 1914. It is the policy of the Cooperative Extension Service of Purdue University that all persons shall have equal opportunity and access to its programs and facilities without regard to race, religion, color, sex or national origin.