One way to improve performance in a herd is through selection of genetically superior animals, with the selection based on an estimate of the genetic merit of the animals. How well this genetic merit is estimated (accuracy) is important, because accuracy predicts the potential rate of genetic progress. The higher the accuracy, the more genetic progress is possible, assuming that the
genetically superior animals have been selected.
Across-herd genetic evaluation programs are used to predict the genetic merit of animals for specific traits. These programs combine records on the individual with information on relatives in an in-depth analysis, resulting in very accurate estimates of genetic merit. The programs typically express the genetic merit of an individual for a trait as an Expected Progeny Difference (EPD), or half of the animal’s breeding value. Across-herd genetic evaluation is the comparison of sires, dams, and pigs
based on the analysis of performance information collected on pigs of the same breed in different herds at many different times. This may include onfarm records, national breed test information, and progeny test data.
Across-herd evaluations can be used to accurately compare animals in different herds. Across-herd evaluations are used routinely by the dairy and beef industries in the U.S. to identify the very best
genetic material in each breed. Canadian pork producers use an across-herd program to select breeding stock. In the U.S., the STAGES program began using an across-herd evaluation in 1991, and has done nightly across-herd evaluations for Yorkshire, Hampshire, Duroc, and Landrace breeds since 1998. There are separate evaluations for each breed.