NUTRITION                                         PIH-112


          Determining the Relative Value of Feeds for Swine

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

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


     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

     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

     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.


     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

     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
 1.           Ingredient            Price/cwt.   Energy     Lysine   Phosphorus
 2.                                     $       kcal/lb.       %          %
 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
 8.                                            (Formula 1)(Formula 2)(Formula 3)
 9.                                            (Formula 4)(Formula 5)(Formula 6)
11.Value of lysine, $/lb.                                 (Formula 7)
12.Value of phosphorus, $/lb.                                        (Formula 8)
13.Value of energy, $/kcal/lb.                 (Formula 9)
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


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culture Cooperating. H.A. Wadsworth,  Director,  West  Lafayette,
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