AS-443
animal sciences beef
Sire selection is one of the most important decisions made by a cow-calf producer. If it is effective, sire selection will account for nearly 90 percent of the genetic improvement in a herd. In herds that produce their own replacement females, 871/2 percent of the heifer’s genetic makeup comes from the last three bulls used in the pedigree.
Sire selection is more accurate today than ever before. Breed associations have developed computer programs that utilize performance records on a calf’s relatives in addition to its own record in calculating estimated breeding values (EBVs). Traits evaluated include, but may not be limited to, birth, weaning, and yearling weights, and maternal breeding value for daughters' calving ease and weaning weight. Using these estimated breeding values in a selection program has improved the accuracy of identifying superior and inferior animals within a producer’s herd.
The development of sire summaries has been a big advancement for the beef cattle industry. Sire summaries have given breeders an opportunity to make more accurate selection decisions. With high costs of production and competition from other meats, cattle producers cannot tolerate mistakes in their breeding programs. Therefore, the ability to utilize sire summaries is important to the individual producer. Mistakes made on sire selection this year will show up in next year’s calf crop. Three years later, the sire's genetic influence will become evident again as his daughters come into production.
Most breed associations now produce and distribute a sire summary. They are updated and printed annually. In most cases they are free to commercial cattle producers. Requests for sire summaries should be made directly to the breed association's office. Traits that are economically important to most cattle producers are evaluated in these summaries.
Most sires listed in the summary have been used in A.I. programs across several herds.
The traits listed vary slightly among breed sire summaries. They all evaluate the ability of a sire to transmit growth rate to his progeny in the areas of birth, weaning, and yearling weights. Most breeds also evaluate the performance of daughters of the sire. This includes an evaluation of daughter calving ease and/or the ability of daughters to wean heavy calves (referred to as Maternal Breeding Value for weaning weight).
Sire evaluation in the beef industry has become a sophisticated procedure developed through experience, research, improved statistical procedures, and the development of large, high speed computers. Fortunately, a beef producer only needs to know a few basic concepts to interpret and use the results.
Terminology
Expected Progeny Difference (EPD)
Sire summaries use the term Expected Progeny Difference (EPD) to express genetic transmitting ability of a sire. The EPD is reported as a plus or minus value in the unit in which the trait is measured, such as pounds for birth weight. An example of the Angus Sire Summary, which is similar to those of other breeds, is shown in table 1. An EPD for yearling weight of -t-70.0 lb. indicates that progeny of this bull should average 70.0 lb. more at 365 days of age than progeny of an average bull of the breed. On the other hand, a bull with an EPD of -2.7 lb. for weaning weight would be expected to produce calves 2.7 lb. lighter at weaning weight than the average bull of that breed. Some breed associations express EPDs as ratios. When ratios are used, conversion factors are given so the ratios can be translated to EPD values. For example, the 1985 Simmental Sire Summary indicates that a one unit
Understanding and using Beef sire Summaries