The worth of individual animals were compared using within-herd ratios. Thus, an animal's relative worth was measured as a percentage difference from the herd average. An EBV is a systematic way to combine information of heritability with the performance of relatives and progeny to define an animal's breeding value. While individual performance records increased the accuracy of selection within a herd, they did little to assist the breeder trying to select bulls from the total population. Within-herd comparisons are useful for selection of replacement females, but breeders who want to make maximum genetic progress need to be able to compare and select superior bulls from the entire population.
Estimates use all available progeny and performance records of close relatives.
EPDs can be calculated for bulls and cows with progeny and all non-parent bulls and females with legitimate records. Non-parent bull and female EPD calculations combine the individual performance and all collateral relative performance. Primary ancestral information going into young non-parent EPD calculations comes from the animal's sire and dam. Producers should not be concerned about the formulas or calculations but should begin to use the information in making replacement selections. The dairy industry has successfully used this approach in its breeding program for years.