The earliest efforts at objective across-herd comparisons utilize central tests. In these tests, young bulls , rams, or boars were brought together in common environment to be evaluated, primarily for growth traits. These tests yield information on only a few traits and all the information is obtained from the individual. Because of these limitations, designed progeny tests were initiated to compare sires via information collected on their respective progeny. Although an improvement, these designed progeny tests were relatively limited in scope and expensive to conduct.