The basic concept of beef cattle performance records is to measure genetic differences between animals for traits of economic importance.
Today’s commercial cattleman has available to him the germ plasm from multiple beef breeds and numerous breeders and animals within each of the breeds to select his herd replacements. Competition for the commercial industry purchasing power between and within breeds is keen and those breeders who can document their seedstock’s performance for the commercial man’s investment have a distinct advantage in today’s beef industry as it moves toward "specification production" from conception to slaughter.
The American Hereford Association recognizes the importance of performance records in today’s beef industry and through Whole Herd Total Performance Records (TPRTM ) can provide a system flexible enough to meet the needs of the most sophisticated record keeping breeder or those who desire to keep only the basics.
WITHIN HERD AND CONTEMPORARY GROUP COMPARISONS
Within herd and contemporary group records generated through Whole Herd TPR include measures for calving intervals, birth weights, weaning weights, yearling weights, scrotal circumference, hip height/frame measures and ratios for most of these measures.
Good within herd records include information obtained at birth, weaning, yearling and ultrasound carcass data as well. These within herd and contemporary group records are adjusted for known environmental sources of variation in animal performance such as age of dam, age of calf, etc.
The large environmental differences that exist between herds and contemporary groups within a herd makes comparisons using ratios and raw data impractical and is an inaccurate way of comparing genetics. EPDs are the most powerful tool presently available for comparing animals across contemporary groups and across herds.
WHAT CONSTITUTES A CONTEMPORARY GROUP?
Contemporary groups are those calves raised together and managed in the same manner so that each calf’s data can be fairly compared against all of the other calves within the group. Contemporary groups are the foundation principle behind EPDs and thousands of such groups are considered in EPD calculations. This wide breadth of data is the foundation for accuracy and allows for comparisons across herds in different regions of the country within the breed.
Performance comparisons with regular Whole Herd TPRTM records should be restricted to animals within a herd and contemporary group. For the records to be meaningful, breeders must pay strict attention to the proper construction of contemporary groups. A contemporary group should consist only of animals of the same sex and management group within a relatively narrow age range in birth dates, not to exceed 90 days.
USING EPDs FOR ACROSS HERD COMPARISONS
Animal comparison across herds and contemporary groups should only be done through Expected Progeny Difference (EPD) values. An EPD is the measured difference of an economically important trait that is expected from the progeny of one animal as compared to the progeny of another animal within the same breed. In other words, EPDs are a prediction of how one animal’s offspring will perform, on the average, as compared to another. Years of research and practical application have proven the importance and reliability of EPDs as a selection tool in the beef cattle industry.
EPD calculations are based upon volumes of weights and measures collected in thousands of herds over many years and processed through breed association performance programs. These calculations include differences within management or contemporary groups and incorporate all available data on a trait into the prediction of an animal’s EPD value for that trait. Performance information used to predict an EPD can come from any combination of the following: 1) progeny 2) relatives in the pedigree, particularly the individual’s sire and dam 3) grand progeny and 4) the individual’s own performance record.
This information is appropriately weighted for the amount of data available in each category in calculating the EPD’s. In addition to the above information, parent EPD values are adjusted for the genetic merit of the animal the parent is bred to, the performance level of other parents with progeny or produce in the same contemporary group, and genetic trends.
Some of the more important traits economically and most easily measured with EPDs are birth weight, weaning weight, maternal milk and milk and growth and have EPDs expressed in pounds. Scrotal circumference is expressed in centimeters. Fat is expressed in tenths of inches, ribeye area (REA) in square inches and %IMF (percent intramuscular fat) is expressed in tenths of a percent difference.
EPD’s predict progeny performance differences and not absolute values. If for example Bull A has a +50 pound yearling weight EPD and bull B has a +20 pound yearling weight EPD, one would expect a 30 pound difference (+50 - +20) in the yearling weight of the two bull’s progeny if both were mated to comparable cows and the resulting calves were of the same sex and were handled alike from birth through yearling.
Along with the EPD calculation itself, a companion calculation is made which determines the accuracy of the EPD. Simply stated, the more data, the more accurate the data becomes and more reliability can be placed upon it. An accuracy expressed as "P" means the EPD is simply a pedigree estimate or the average of the sire and dam EPDs, whereas a "P+" is an interim or pedigree estimate EPD factored by the animal’s own individual performance data for that trait. Numerical accuracy values range between 0 and 100 percent and consider data from the individual, it’s progeny, it’s ancestors and the ancestor’s familial ties.
EPD values are the best predictor of the performance of an animal’s future progeny in comparison with progeny of other animals in the breed. EPD values have been shown to be from five to nine times more accurate for animal selection than any other available performance data.
EPDs for the Hereford breed are calculated twice annually with interim EPDs being calculated throughout the year. Registration certificates issued by the AHA for performance registry breeders always contain the most current EPDs as of the date of issue.
SEEDSTOCK BREEDER’S ROLE
The primary responsibility for maintaining and improving the traits associated with efficient production lies in the hands of seedstock producers. Genetic change in the commercial beef cattle population is controlled by the genetic merit of bulls produced by the seedstock producer and used by the commercial cattleman. Whole Herd TPRTM records and EPD values used with sound judgment can provide performance documentation for building a total breeding program for the registered Hereford breeder and his commercial customers.