Expected Progeny Difference (EPD) in Beef Cattle

The first performance records of beef cattle were primarily weights or weight gains measured at weaning or yearling ages. Sound comparisons of individuals were often impossible because of sources of variation, such as age, sex, age of dam, and management conditions. Although standard adjustments were developed to account for some of these variations, this was not always possible, especially for differences in management, location, season, and year. Even with appropriate adjustments, it was still necessary to limit comparisons to animals managed alike in a contemporary group. To facilitate comparisons, ratios of performance within a contemporary group were sometimes calculated, but these ratios still contained unaccounted-for differences between groups.