Economic Value of Pork Quality Traits

Todd See, Kelly Zering and O.W. Robison
North Carolina State University

Introduction

"Pork Quality" means different things to producers and consumers. Pork producers desire lean high yielding carcasses in a package that is economical to produce. Packers and retailers want a product with attractive appearance that has high yields and is stable in cold storage. Consumers might define quality as visual appeal, eating satisfaction, food safety, nutritional value, or even animal welfare. The ultimate objective of the pork industry is to provide protein to people, therefore, desirable quality is a combination of traits that provides an edible product that is nutritious and wholesome after processing and storage, attractive in appearance, and appetizing and palatable after cooking. In addition quality must be consistent.

It is essential to emphasize more than one trait in pork production. However, the potential for selection should not be dissipated on unimportant traits. Selection for traits that are economically unimportant, extremely low in heritability or adversely correlated with other important traits will reduce the selection intensity for more important traits. For these reasons selections should be made using an index or total score that combines each trait with its economic value and the correlation that it has with the other traits in the index.

The objective of this presentation are to:

What are Economic Values ?

The economic value for each individual genetic trait is intended to represent the expected change in producer profit for a unit change in the trait. In general, the method of calculating economic value is to estimate the marginal costs that are saved by superior performance. There are a range of estimates of economic values of traits and they are likely to vary across regions, markets and production systems. The economic value of various genetic traits will also vary from farm to farm.

Muscle quality traits have only recently been considered in U.S. genetic selection criteria (Genetic Evaluation: Terminal Line Program Results). Economic values for days to 250 pounds (D250), loin muscle area (LMA), pH, intramuscular fat (IMF), INSTRON (TEND), and drip loss (DRIP) are presented by Goodwin and Lawrence. Melton and Huffman also present economic values for pH, percent lipid, and Instron score. Goodwin and Lawrence present estimates of the economic value of the halothane gene.

The results of the consumer preference study (Pork and the U.S. Consumer Conference) provide an indication of the economic value of marginal changes in meat quality traits. Considerable uncertainty remains about how much of a premium pork marketers can collect for differentiated pork products and what volume they can sell at that price. Considerable uncertainty also exists about the costs that marketers will incur to distinguish their products and how much of a premium they will pass through to packers and producers. It is also known that losses occur during slaughter and processing due to poor pork quality. However, the magnitude of this losses is not known. Another loss that can occur is when a consumer dissatisfied with the pork product never purchases pork again, this too is hard to measure. Ultimately a producer must make genetic choices based on available incentives.

Traits Evaluated

Traditional growth and carcass traits and measure of muscle and eating quality were considered in the present study. Growth and carcass traits of swine included feed to gain (F/G), average daily gain (ADG), days to 250 pounds (D250), backfat probe at the tenth rib (BF10) and loin muscle area (LMA).

The muscle quality traits can include ultimate pH (PH) that indicates eating quality and shelf life. Lower PH is related to greater losses during further meat processing and high PH is related to shorter shelf life but also better eating quality. PH is also becoming more practical for measurement in commercial plants with the advent of solid-state pH electrodes.

Percentage drip loss (DRIP) is a measure of the amount of free moisture on the freshly cut loin surface and is measured using filter paper.

Intramuscular fat percentage (IMF) of the loin muscle in this case is measured as the total lipid percentage of the uncooked loin on a wet or as is basis. European scientists believe at least 2% IMF is needed to produce consumer acceptable pork loins. However, the positive correlation's between IMF and BF10 indicate that with increased IMF there will also be increased backfat.

Cooked pork loin tenderness (TEND) is measured by the Instron Universal Testing Machine star probe in kilograms of pressure. The Instron measure has high repeatability and is related to sensory panel tenderness scores. Low Instron scores (less kg pressure) indicate more tender pork.

The color of the lean (COLOR) is measured by the Minolta 310 chromameter as light reflectance of the loin muscle measured at the tenth rib. Consumers find both very dark (down to 12) and very pale (up to 36) meat unacceptable. However, consumers most importantly desire uniformity of color. The Minolta has proven to be a reliable indicator of meat quality, especially of pale meat which may become low quality, pale, soft, and exudative. Because of COLORs relationship with other quality traits and its potential to be measured at chain speed in the slaughter plant its most important role for selection may be in correlated response for other traits.

Economic Values

Economic values are presented for each trait in Table 1. In this table the economic value is the marginal savings in cost due to superior performance. The economic value is then divided by the SD for the trait to put all value in the same units of measure. Finally the relative economic value is calculated by setting one trait as the basis by which all comparisons will be made. In this example BF10 is set as the base trait and therefore has a relative economic value of $1.00. The relative economic values indicate how much additional profit can be earned by making an improvement of one standard deviation in one trait versus another trait. Relative economic values also indicate what profit is possible by genetic selection for each trait.

Table 1. Economic Values


                                                Economic Value/       Relative      
 Trait      Units       SD    Economic Value          SD           Economic Value   

  F/G   lb. feed/lb.    .25       -$18.00            $4.50              $1.50       
            gain                                                                    

  ADG      lb./day      .20        $3.00             $0.60              $0.20       

 D250       days        13        -$0.12             $1.56              $0.52       

 BF10        in.        .20       -$15.00            $3.00              $1.00       

  LMA      sq. in.      .80        $5.68             $4.54              $1.51       

  PH       pH unit      .25       $33.80             $8.45              $2.82       

 Drip         %        1.35       -$0.82             $1.11              $0.37       

  IMF         %        1.00       $17.00            $17.00              $5.66       

 Tend        kg.       1.10       -$5.00             $5.50              $1.83       

For this set of economic values, in this situation, a pork producer would capture the marginal value of the quality traits if the value of the trait is first captured by the retailer and ..... if the marginal value of the trait is passed through to packer and producer, and .....if the trait can be measured, then ..... there is the potential for the producer to achieve some premium/discount.

Phenotypic and Genetic Parameters

Table 2 presents the heritabilities, genetic and phenotypic correlations for this set of terminal traits. The growth traits, pH, TEND, COLOR and DRIP are all moderately heritable. While the carcass traits and intramuscular fat are highly heritable. Important correlations between growth and carcass traits to be aware of are the adverse relationships between F/G and the traits ADG, D250 and LMA. A desirable relationship exists between BF10 and the traits of F/G and LMA.

For the muscle quality traits, IMF has an adverse relationship with BF10 and LMA. However a desirable relationship has been observed between pH and the other quality traits of DRIP, TEND, and COLOR. COLOR also has a positive relationship with DRIP.

Table 2. Parameter Estimates1.


  Trait    F/G   ADG    D250    BF10    LMA    PH    DRIP    IMF     TEND     COLOR   

   F/G     .30   -.70    .65     .34    -.35    0      0      0       0         0     

   ADG    -.65   .30    -.90     .14    -.13  -.11    .07    .06     -.07      .11    

  D250     .60   -.87    .30    -.05    .05    .10   -.06    -.09    .07      -.11    

  BF10     .25   .20    -.18     .52    -.61   .03   -.05    .30     -.17      .09    

   LMA    -.20   -.06    .03    -.35    .47   -.11    .13    -.25    .15      -.06    

   PH       0    -.08    .09     .08    .01    .38   -.50     0      -.42     -.66    

  DRIP      0    .06    -.06    -.06    .13   -.50    .16    .05     .22       .49    

   IMF      0    .07    -.07     .30    -.25   .01   -.28    .47     -.17      .15    

  TEND      0    -.06    .06    -.16    .13   -.37    .19    -.11    .20       .23    

  COLOR     0    .09    -.07     .08    -.05  -.54    .50    .12     .19       .29    

1 Heritability estimates are on the diagonal. Genetic correlations are in the upper portion. Phenotypic correlation's are in the lower portion. Sources: Genetic Evaluation: Terminal Line Program Results (1995), Genetics of Swine , and Guidelines for Uniform Swine Improvement Programs (1987).

Evaluating Multiple Traits

Overall profitability is influenced by many factors. Several traits need to receive emphasis in a well-designed breeding program. The difficulty is determining the appropriate emphasis to place on each trait. Traits are measured in different units (number of pigs, pounds per day, inches, etc.), are not of equal economic importance, and are not genetically influenced to the same degree (different heritabilities). These factors make it a difficult problem to determine the appropriate emphasis to apply to each trait in a breeding or selection program. Selection indexes are used to assign emphasis to each trait and provide a single value to use when comparing animals. Commonly used examples of indexes are the Sow Productivity Index (SPI) that includes NBA and LW21 and the Terminal Sire Index (TSI) that includes BF10 and DAYS. The weights assigned to traits included in selection indexes represent the expected change in producer profit for a unit change in each trait. The index weights differ from economic values since they include the heritability of each trait, correlations with traits excluded from the index, and the economic values of traits excluded from the index.

Table 3 shows the selection indexes for ranking animals on a combination of the four common growth and carcass traits; F/G, D250, BF10 and LMA. The information presented in tables 1 and 2 was used to construct the weights presented for the various indexes. The rIH is an estimate of the accuracy level that phenotypic measurements of the traits included in the index predict the true genetic merit of the individual. In this example using measures of all four traits on an animal (index 1) results in an accuracy of .74 when F/G is not measured on the individual but is predicted through the correlations with the other three traits the accuracy is .73. This difference in accuracy of .01 indicates that given high costs to measure feed to gain the benefit in increased accuracy is very low.

Table 3. Indexes for growth and carcass traits.


      F/G     D250     BF10    LMA    r1H   

 1   -2.58    -.11    -13.41   3.22   .74   

 2            -.14    -14.98   3.30   .73   

 3            -.15    -19.18          .62   

 4                    -17.48          .55   

 5            -.09                    .19   

Table 4 describes possible indexes for ranking animals on a combination of eight traits incorporating growth, carcass and muscle quality measures. Information from tables 1 and 2 was used to construct the weights presented for the various indexes. Using the accuracy value as a guide this table suggests that the index to best predict genetic merit for this set of eight traits is index 2. Index 2 includes phenotypic measure of D250, BF10, LMA, PH and IMF.

Table 4. Indexes for growth, carcass and muscle quality traits.


          F/G      D250     BF10     LMA       PH      DRIP     IMF     TEND     r1H    

   1     -8.54     .05     -12.79    1.78    22.21     3.09    9.40     -.96     .71    

   2               -.07    -14.34    2.48    16.11             8.48              .65    

   3               -.04    -11.97    2.71                      8.45              .58    

   4               -.08    -4.23     .72     15.92                               .30    

   5               -.05    -1.91     .95                                         .08    

   6                                                           7.23              .52    

Examples of Comparing Sires

Economic values can and should be used with EPDs and other genetic information to determine value and price. Commercial producers can use economic values for traits to decide how much they are willing to pay for boars and gilts. Seedstock suppliers can also use economic values for trait in indexes for pricing. Genetic information combined with economic values can be used to determine if you are getting value for your money. The values in Table 1 are some standard economic values for terminal traits. If you know or can arrive at a value for these traits in your individual situation that would be more accurate. Two potential AI sires will be compared in the following examples using index 2 from Tables 3 and 4.

In the following examples boars of two breeds are compared using the NGEP results. It is important to note that these results can only be used to make comparison across breeds if the base year for genetic evaluations is the same in each population. In these examples Duroc and Hampshire have the same base year.

Example 1. Growth and Carcass Traits

Objective: Selection of Hampshire or Duroc boar to purchase semen from as a terminal sire.

Least Square Means From NGEP Results:

Hampshire breed: D250 = 175.4, BF10 = 1.0, LMA = 6.58

Duroc breed: D250 = 169.7, BF10 = 1.13, LMA = 6.14

Breed Dollar value per pig using Growth and Carcass Index 2:

Hampshire breed: Table 3, Index 2 = $4.26

Duroc breed: Table 3, Index 2 = $1.66

Individual Boar EPDs from Association Sire Summaries with Genetic Base of 1992:

Hampshire Boar EPDs: -4.4 D250 and 0.00 BF10.

Duroc Boar EPDs: -1.2 D250 and -.06 BF10.

Expected value per pig produced:

Hampshire boar Value per pig produced: $4.26 + (-4.4 x -$.12) + (0 x $15.00) = $4.79

Duroc boar Value per pig produced: $1.66 + (-1.2 x -$.12) + (-.06 x $15.00) = $2.70

If the selected boar is used to produce 1600 market hogs the advantage of the Hampshire boar would be: ($4.79 - $2.70) X 1600 = $3,344.00

Example 2. Growth, carcass and muscle quality traits.

Objective: Selection of Hampshire or Duroc boar to purchase semen from as a terminal sire.

Least Square Means From NGEP Results:

Hampshire breed: D250 = 175.4, BF10 = 1.0, LMA = 6.58, pH = 5.7, IMF = 2.57

Duroc breed: D250 = 169.7, BF10 = 1.13, LMA = 6.14, PH = 5.85, IMF = 3.03

Breed Dollar value per pig using Growth and Carcass Index 2:

Hampshire breed: Table 4, Index 2 = $.66

Duroc breed: Table 4, Index 2 = $5.31

Individual Boar EPDs from Association Sire Summaries with Genetic Base of 1992:

Hampshire Boar EPDs: -4.4 D250 and 0.00 BF10.

Duroc Boar EPDs: -1.2 D250 and -.06 BF10.

Expected value per pig produced:

Hampshire boar Value per pig produced: $.66 + (-4.4 x -$.12) + (0 x $15.00) = $1.18

Duroc boar Value per pig produced: $5.31 + (-1.2 x -$.12) + (-.06 x $15.00) = $6.35

If the selected boar is used to produce 1600 market hogs the advantage of the Duroc boar would be: ($6.35 - $1.18) X 1600 = $8,272.00

At this time, producers should use caution in interpreting the muscle carcass and muscle quality economic values. Producers currently selling hogs through a carcass merit program can use their discounts for backfat and loin muscle area to calculate economic values for those traits. The relative economic values and the relatively high heritability of backfat and loin muscle area make them important traits in evaluating terminal sires.

No incentives are currently available to producers for muscle quality traits such as intra muscular fat, pH, and tenderness. The Consumer Preference Study indicates that pork marketers have an opportunity to earn considerable profits by creating differentiated products with specified pH, IMF, and tenderness. In order to assure consistent quality in these products, packers and processors will need to establish inexpensive measurements of these traits. In order to procure a reliable supply of pork with desired traits, packers will have to offer premiums for them. However, it is important to realize that what consumers preferred to eat what not necessarily the same product they selected based on visual appearance. In addition, some "quality" measures have different values for eating and processing.

A fundamental problem facing the industry now is that current carcass merit programs create incentives for selecting for less backfat. The positive correlation between backfat and intramuscular fat means that selection for less backfat alone will result in less intramuscular fat. The positive correlation between backfat and F/G provides further incentive to select against IMF. The Consumer Preference Study indicates that consumers prefer to eat pork with total lipids greater than 4 percent. To maintain a desirable level of IMF, packers will have to pay sufficient incentives to offset the costs of higher F/G and the discounts for higher BF10. Producers may wish to collect information on IMF, pH, and tenderness for terminal boars and their market hogs. Producers of hogs with poor muscle quality traits may wish to begin selecting for improvement in these traits.

Bottom Line

Swine producers must select genetic stock that maximizes their profits. Genetic selections will affect profits for hogs sold one year later (in the case of terminal sires) to two or more years later in the case of maternal line sires. Producers should select stock using the economic values that are currently available to them but attention should be paid to the muscle quality traits as well. It is likely that premiums and discounts for muscle quality traits will be introduced in the "immediate" future.

A program is needed that allows producers to evaluate genetic stock in the context of their current herd performance and in the context of their current marketing alternatives. The need for such a program is even greater when muscle quality traits are considered. While increases in intramuscular fat and pH may be desirable over some range, excessive levels of these traits can be undesirable. A program would allow producers to reduce selection pressure for IMF and pH as herd levels of these traits attain ideal levels and where further increases would reduce meat value. Similarly, there is little value attached to changes in color except when color is extremely light or extremely dark. A program would also allow selection against extremes in meat color.

Number born alive and feed conversion remain important variables in reducing production costs. Carcass quality traits such as backfat, loin muscle area, and yield are important for producers selling through carcass merit programs. Meat quality traits including intramuscular fat and pH will be important in determining hog price and profits in the near future and perhaps in maintaining a market in the more distant future.

Key Points

References

Goodwin, R. and S. Burroughs (eds.) 1995. Genetic Evaluation: Terminal Line Program Results. National Pork Producers Council, Des Moines IA.

Goodwin, R and J. Lawrence. 1995. In: Genetic Evaluation: Terminal Line Program Results. National Pork Producers Council, Des Moines IA. pp 261-268.

Melton, B. E. and W.E. Huffman. 1995. In: Genetic Evaluation: Terminal Line Program Results. National Pork Producers Council, Des Moines IA. pp 269-308.

NPPC. Pork and the U.S. Consumer Conference. National Pork Producers Council, Des Moines, IA.

NSIF. 1987. Guidelines for Uniform Swine Improvement Programs.

Young, L.D. (ed.). 1989. Genetics of Swine. USDA-ARS. Clay Center, NB.