epd glossary
Calving Ease Direct (CE) A higher value indicates greater calving ease. It predicts the average difference in unassisted births with which a sire’s calves will be born when bred to first-calf heifers. Birth Weight (BW) The expected difference in average birth weight (pounds) of progeny. Birth weight reflects prenatal growth. Weaning Weight (WW) The expected difference in average weaning weight of calves. The evaluation reflects the genetic influence on pre-weaning growth rate. Yearling Weight (YW) The expected difference in average yearling weight of progeny. The evaluation reflects genetic influence on both pre-weaning and post-weaning growth rate. Maternal Milk (Milk) The genetic ability of a sire’s or dam’s daughters to express in pounds of weaning weight in her calves due to her maternal ability through mothering instinct and milk. Scrotal Circumference (SC) The expected difference in scrotal circumference (expressed in centimeters) of a bull’s or dam’s male offspring at yearling compared to progeny of all other animals evaluated. Research has also indicated a relationship between increased SC EPD and decreased age at puberty for daughters. Carcass Weight (CW) Carcass Weight EPD are expressed in pounds and is a predictor of the differences in hot carcass weight between parents progeny at an age constant endpoint. Ribeye Area (REA) Ribeye area is a major component of the USDA yield grade equation and selection for increased ribeye area should result in larg- er ribeyes and lower yield grades between animals with the same carcass weight. Ribeye Area EPD are expressed in square inches. Fat Thickness (FAT) Fat thickness is the primary component to the USDA Yield Grade equation. Fat thickness has a negative relationship to cut- ability; therefore, selection base on decreased fat thickness should result in lower yield grades and leaner cattle given the same age endpoint. Fat Thickness EPD are expressed in inches. Marbling Score (MARB) Marbling is a subjective measure of the amount of intramuscular fat in the ribeye muscle. Marbling score is the primary component of USDA Quality grade and selection for increased Marbling Score EPD should result in cattle with higher quality grades at the same age endpoints. Charolais Breed EPDs Terminal Sire Index (TSI) The AICA Terminal Sire Index (TSI) is a formal method of combing Expected Progeny Differences (EPD) – BW, WW, YW, REA, CW, MARB and FAT – into one single value on which to base selection decisions. The TSI represents a dollar index per terminal progeny produced for a bull in the AICA database, ranking them for profit potential. This dollar index is to be interpreted much like single trait EPD. For example, if Sire A’s index is $191.66 and Sire B’s index is $200.00, then we would expect Sire B’s offspring to average $8.34 more net return ($200.00 minus $191.66) than Sire A’s offspring. angus Breed EPDs Claw Set (Claw), is expressed in units of claw-set score, with a lower EPD being more favorable indicating a sire will produce progeny with more ideal claw set. The ideal claw set is toes that are symmetrical, even and appropriately spaced. Foot Angle (Angle), is expressed in units of foot-angle score, with a lower EPD being more favorable indicating a sire will produce progeny with more ideal foot angle. The ideal is a 45-degree angle at the pastern joint with appropriate toe length and heel depth. $Value indexes, an economic selection index allows multiple change in several different traits at once pertaining to a specific breeding objective. The $Value is an estimate of how future progeny of each sire are expected to perform, on average, compared to progeny of other sires if the sires were randomly mated to cows and if calves were exposed to the same environment. Maternal Weaned Calf Value ($M), an index, expressed in dollars per head, predicts profitability differences from conception to weaning with the underlying breeding objective assuming that individuals retain their own replacement females within herd and sell the rest of the cull female and all male progeny as feeder calves. The model assumes commercial producers will replace 25% of their breeding females in the first generation and 20% of their breeding females in each subsequent generation. Traits included are as follows: calving ease direct, calving ease maternal, weaning weight, milk, heifer pregnancy, teat size, udder suspension, functional longevity, docility, mature cow weight, claw set and foot angle. Weaned Calf Value ($W), an index, expressed in dollars per head, to predict profitability differences in progeny due to genetics from birth to weaning. The underlying objective being producers will retain 20% of the female progeny as replacements and sell the rest of the cull females and their male counterparts as feeder calves. Traits included are as follows (in no particular order): birth weight, weaning weight, milk, and ma- ture cow weight. Beef Value ($B), a terminal index, expressed in dollars per carcass, to predict profitability differences in progeny due to genetics for postwean- ing and carcass traits. This terminal index assumes commercial producers wean all male and female progeny, retain ownership of these animals through the feedlot phase and market these animals on a carcass grid. Traits included in the index are as follows: yearling weight, dry-matter intake, marbling, carcass weight, ribeye area and fat. Combined Value ($C), an index, expressed in dollars per head, which includes all traits that make up both Maternal Weaned Calf Value ($M) and Beef Value ($B) with the objective that commercial producers will replace 20% of their breeding females per year with replacement heifers re- tained within their own herd. The remaining cull heifer and steer progeny are then assumed to be sent to the feedlot where the producers retain ownership of those cattle and sell them on a quality-based carcass merit grid. Expected progeny differences directly influencing a combined index: calving ease direct, calving ease maternal, weaning weight, yearling weight, maternal milk, heifer pregnancy, teat size, udder suspension, functional longevity, docility, mature cow weight, foot angle, claw set, dry matter intake, marbling, carcass weight, ribeye area, and fat thickness.
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