• EPD DEFINITIONS AND TERMS •
SIMMENTAL BULLS EPD DEFINITIONS AND TERMS Expected Progeny Differences (EPDs): EPDs are the most accurate and effective tool available for comparing genetic levels. In using EPDs, the difference between two sires’ EPDs represents the unit difference expected in the performance of their progeny. For example, if sires A and B have EPDs of +10 and -5, a 15-unit difference would be expected in their progeny (moving from -5 to +10 yields 15 units). Key to using EPDs is knowing in what units they are expressed. For example, if the above case referred to weaning weight EPDs, sire A would be expected to sire 15 pounds more weaning weight than sire B. If calving ease was the trait, sire A would be expected to sire 15 percent more unassisted births in first-calf heifers; in other words, if sire B sired 30 assists in a group of 100 heifers, we would expect sire A to require 15 assists. A percentile-ranking chart is required to determine where a bull’s EPDs rank him relative to other bulls in the breed. For more detailed information about EPDs and $ indexes, visit www.simmental.org. Listed below are the units in which ASA EPDs are expressed, you can find the full list online: Calving Ease (CE): Percent of unassisted births when used on heifers. Birth Weight (BW): Pounds of birth weight. Weaning Weight (WW): Pounds of weaning weight. Yearling Weight (YW): Pounds of yearling weight. Milk (MLK): Pounds of weaning weight due to milk. Carcass Weight (CW): Pounds of carcass weight at 475 days. Maternal Calving Ease (MCE): Percent of unassisted births in first-calving daughters. Yield Grade (YG): Carcass yield grade score at 475 days. Marbling (MRB): Carcass marbling score at 475 days. Ribeye Area (REA): Square inches of carcass ribeye at 475 days. Warner-Bratzler Shear Force (WBSF): Pounds of force required to shear a ribeye steak. All-Purpose Index (API): Dollars per cow exposed under an all-purpose-sire scenario. (See $ Indexes for more details.) Terminal Index (TI): Dollars per cow exposed under a terminal-sire scenario. (See TI for more details.)
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