NUTRITION
PIH-112
pork industry handbook
PURDUE UNIVERSITY COOPERATIVE EXTENSION SERVICE • WEST LAFAYETTE, INDIANA
Determining the Relative Value of Feeds for Swine
Authors
Emmett J. Stevermer, Iowa State University
C. Ross Hamilton, S. Dakota State University
Nathan T. Moreng, University of Idaho
Matthew J. Parsons, Hadley, Massachusetts
T. D. Tanksley Jr., Texas A&M University
Reviewers
Frank Bischoff, Fallon, Nevada
Joe Crenshaw, N. Dakota State University
Louis Malkus, University of Connecticut
Gary Parker, University of Kentucky
Gerald Shurson, Ohio State University
Introduction
Research work conducted during the previous 50 years has defined the nutrient requirements of swine for most stages of production. Nutrient analyses of various feedstuffs indicate that there are a large number of feed ingredients that could be used in swine diets to meet the nutritional requirements of pigs. However, the price relationships among the various ingredients may vary considerably during any given season, year, or locality; and as a result, opportunities to reduce feed costs by substituting one feed ingredient for another often occur. But even so, feed manufacturers and pork producers must evaluate the cost effectiveness and feeding value of various ingredients in order to formulate cost effective and nutritionally adequate swine diets.

Least-Cost Formulations
Linear programs on computers have made it possible to design diets that will meet all minimum nutritional requirements of swine at the least cost. Least-cost formulation techniques are helpful to feed manufacturers and pork producers who maintain inventories of a large number of ingredients or who frequently purchase and sell large quantities of them. Least-cost formulating is of limited value to pork producers who have limited access to many ingredients or have processing systems designed to handle only a small number of ingredients. Least-cost programs usually select the combination of ingredients that give the lowest cost for the diet, not necessarily the ones that result in the lowest cost per unit of gain.

Least-Cost Alternatives
Energy sources, protein, and phosphorus are the three most costly items of the total diet. Ingredients which supply energy make up the major portion of any swine diet and usually account for the majority of the cost of that diet. Feed grains are typically used as the major source of
dietary energy for all classes of swine. Each type of grain has certain unique physical and chemical characteristics which affect its value as swine feed. Other publications in the PIH series (provided at the end) deal with limitations and special precautions that need to be recognized when using one or more alternative feeds in swine diets.

The second major cost of diets is incurred from supplemental proteins. Actually, it is the lysine in the protein source that determines the amount of the protein source needed in most swine diets. Lysine is the essential amino acid most likely to be deficient in grain-based diets fed to swine. The percentage of lysine found in grain varies considerably, and it is not directly related to the percentage of protein found in the grain. Because of this, swine diets should be formulated and ingredients evaluated on a lysine rather than protein basis.

The third major contributing factor to the total diet cost is the supplemental phosphorus source. There is considerable variation in the availability of phosphorus in feedstuffs. If the available phosphorus values of the ingredients and the requirements, expressed on the same basis, for the pigs are known, they should be used in determining the relative value of potential feedstuffs.

In addition to sources of energy, lysine, and phosphorus, other ingredients contribute to the cost of the diet, but their contribution is relatively small because of the small amounts used and/or the ingredients are not very expensive. Vitamins, trace minerals, salt, and calcium fit into this category. The vitamin content of grains and supplemental protein sources is variable, and their content may decrease rapidly during storage. Therefore, the vitamin content of stored feedstuffs may be of little nutritional value. Feed additives, such as antibiotics and chemotherapeutics, also contribute to the total cost of the diet. The decision of which feed additives to use and when they should be used is dependent upon the cost effectiveness of including feed additives in swine diets.

In the major swine producing regions, there are usually one or two major sources of energy and only two or
Cooperative Extension work in Agriculture and Home Economics, state of Indiana, Purdue Univeristy 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.