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.
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Column: A B C D E
Row
1. Ingredient Price/cwt. Energy Lysine Phosphorus
2. $ kcal/lb. % %
3.
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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)
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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
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