NUTRITION PIH-112 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. How- ever, 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 effec- tiveness 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 formulat- ing 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 typi- cally 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 recog- nized 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 defi- cient 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 require- ments, 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 three ingredients used as sources of supplemental protein. In the corn belt, corn is often the most economical source of energy for swine diets, and soybean meal is usually the most economical source of supple- mental protein. Generally, the most economical standard phos- phorus source for swine diets is dicalcium phosphate. The pro- ducer must decide whether alternative feed ingredients might be used in place of those that are most readily available. For exam- ple, is corn a more economical feed ingredient than oats? There are nutrient-compositional differences between the two feedstuffs, but for all practical purposes, it is the energy con- tent, lysine, and phosphorus differences that contribute to their value in swine diets. Therefore it is important to determine and compare the economic value of the energy content, lysine, and phosphorus in order to determine which is the more economical feedstuff. If the prices of the three reference feedstuffs such as corn, soybean meal, and dicalcium phosphate are known, the value of each nutrient can be calculated. These values can then be applied to the composition of each comparable feedstuff to deter- mine the relative value of that feedstuff. The feedstuff that provides the most nutritive value for the least cost is the ingredient to choose. The levels of protein, amino acids, fiber, vitamins, and mineralsas well as the pigs' ageshould all be con- sidered when comparing ingredients for use in swine diets. Calculations The calculations used to determine values for energy con- tent, lysine, and phosphorus are based upon prices of three diet ingredients and involve the solving of simultaneous equations. Corn, soybean meal (44% protein), and dicalcium phosphate are used as the reference feedstuffs in the example used in Table 1. The example uses metabolizable energy, total lysine, and total phosphorus values of air-dry ingredients. Other ingredients and other prices and composition of the ingredients can be used if desired. Solving the simultaneous equations for the economic value of energy content, lysine, and phosphorus allows the determination of the value of any potential feed ingredient. These calculations can be easily handled by programmable calculators and small micro computers and can then be carried out on a regular basis at a minimal cost. The following values should be obtained for the respective formulas when ingredient composition values are the same as those used in Table 1. Using the Values Whenever a potential feed ingredient can be added to a swine diet at a lower price than its calculated nutritive value, it is an economical substitute for some of the ingredients that were used in making the comparison. For example, if oats would have a nutritive value of $2.51 per cwt. and could be added to a diet at a cost of $2.30 per cwt. ($0.74 per bushel), then one could for- mulate a more economical swine diet by using some oats and less corn, soybean meal, and dicalcium phosphate. The resulting diet would be lower in energy content and more diet would be required to produce a unit of weight gain, but the diet cost per unit of gain would be less. Related Publications PIH-3 Energy for Swine PIH-5 Protein and Amino Acids for Swine PIH-7 Principles for Balancing a Ration PIH-23 Swine Rations PIH-52 Minerals for Swine PIH-71 Physical Forms of FeedFeed Processing for Swine PIH-73 High-Moisture Grains for Swine PIH-108 By-Products in Swine Diets NEW 11/87(5M) Table 1. Spreadsheet program for use with micro computers. ________________________________________________________________________________ Column: A B C D E Row 1. Ingredient Price/cwt. Energy Lysine Phosphorus 2. $ kcal/lb. % % 3. ________________________________________________________________________________ 4.Corn $ 2.50 1500 .25 .25 5.Soybean meal (44%) $10.00 1475 2.88 .60 6.Dicalcium phosphate $15.00 0 0 18.50 7. 8. (Formula 1)(Formula 2)(Formula 3) 9. (Formula 4)(Formula 5)(Formula 6) 10. 11.Value of lysine, $/lb. (Formula 7) 12.Value of phosphorus, $/lb. (Formula 8) 13.Value of energy, $/kcal/lb. (Formula 9) 14. 15.Composition of feed in question: 1220 .34 .33 16.Relative value of above feed: (Formula 10) ________________________________________________________________________________ Formulas for the above locations Values Formula 1:@SUM(D4...D6)/@SUM(C4...C6) 0.0011 Formula 2:@SUM(E4...E6)/@SUM(C4...C6) 0.0065 Formula 3:@SUM(B4...B6)/@SUM(C4...C6) 0.0092 Formula 4:((C4*D8)-E4) 9.5063 Formula 5:((C4*C8)-D4)/C9 0.1397 Formula 6:((C4*@SUM(B4...B6)/@SUM(C4...C6))-B4)/C9 1.1956 Formula 7:((C5*E8)-B5-(E9*C5*D8)+(E9*E5)) / (((C5*C8)-D5)-(D9*C5*D8)+(D9*E5)) 2.7540036 Formula 8:(B4+(C4*((D11*C8)-E8)-(D11*D4)))/(E4-(C4*D8)) 0.8108108 Formula 9:(@SUM(B4...B6)/@SUM(C4...C6))-(C8*D11)-(D8*E12) 0.0010725 Formula 10:(C15*C13)+(D15*D11)+(E15*E12) 2.51 ________________________________________________________________________________ ______________________________________________ Cooperative Extension Work in Agriculture and Home Economics, State of Indiana, Purdue University and U.S. Department of Agri- culture Cooperating. H.A. Wadsworth, Director, West Lafayette, IN. 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 our programs and facilities. .