U.S. National Genetics Evaluation

The American Duroc, Hampshire, Landrace and Yorkshire breeds have been utilizing a national genetic evaluation system for several years now. Over 500,000 individual records are in the data bank for growth, backfat and reproductive traits. The data are analyzed using BLUP (Best Linier Unbiased Predictive) genetic evaluation procedures. This animal model technology is the most accurate technology available for the evaluation of genetic merit. The individual's own record, records on ancestors in the individual's pedigrees, any collateral relatives with performance records (littermates, half sibs, etc) as well as records on any progeny of the individual are utilized. This multiple trait procedure is used for genetic evaluation of reproductive traits (Number Born Live and 21-Day Litter Weight) and growth traits (Days to 230 and Backfat). The sources of variation accounted for in the analysis models include the major sources that influence animal performance (contemporary group, sire, dam, permanent environment, maternal effects and service sire). This allows for the direct comparison of all sires evaluated.

TERMINOLOGY USED IN THIS MANUAL

STAGES
Data listed under the heading STAGES is based on the individual's own record and that of relatives. In this case the sire does not have progeny with performance records. In most cases these sires are not old enough to have sufficient accumulated progeny records.

 ACROSS-HERD SIRE SUMMARY
Data is listed under this heading only if the sire has progeny that have been tested under the National Evaluation System and this performance included in the sire evaluation. 

EPDS
The Expected Progeny Difference (EPD) is a prediction of the progeny performance of an animal compared to the progeny of an average animal in the population (Duroc, Hampshire, Landrace or Yorkshire breeds) based on all information currently available. As indicated above, the major sources of variation are accounted for including contemporary group and herd differences in the BLUP analysis. This allows for direct comparison of all sires. These EPDs are expressed as a plus or minus for Number Born Live, 2 1 -Day Litter Weight, Days to 230 lb. (1 05 kg) and Backfat. Negative EPDs are desirable for Days and Backfat while positive EPDs are desirable for Number Born Live and 21-Day Litter Weight.

Sire A's progeny will require 5.0 less days to 230 lbs. than Sire B. However, daughters of Sire B would produce litters 8 lb. heavier at 21 days than Sire A.

INDEXES
Selection indexes are calculated from the EPDs according to the economic value associated with cost of production and value of market pigs in a typical Midwestern farrow to finish pork production facility. Three indexes are calculated:

Terminal Sire Index (TSI) - It ranks animals on Days to 230 and Backfat EPDs only. It does not include maternal data.

Sow Productivity Index (SPI) - It ranks individuals by Number Born Alive and 21-Day Litter Weight EPDs only. It does not include growth or backfat data.

Maternal Line Index (MLI) - It utilizes the EPDs for both growth (Days and Backfat) and maternal (Born Alive & Litter Weight).

All indexes are scaled so that the average parent has a value of 100 while superior parents have a value greater than 1 00. Which index to utilize will depend on a herd's individual needs and whether the sire is to be used for terminal or maternal line production.

In most commercial pork production systems, sires to be utilized to produce replacement females should be selected on MLI while sires utilized to produce market animals should be selected on TSI.