Date of this Version
Agricultural Research Service, U.S. Department of Agriculture (April 1976).
Because of the large number of combinations of production resources and variations in beef market requirements, one type of cattle will not be most efficient in all production systems. The wide spectrum of cattle types available in the world offers the opportunity of quickly matching genetic resources with production and market requirements. Characterization of available genetic resources for economically important traits is necessary if we are to use this opportunity wisely. Initially, change in production characteristics can be made more rapidly by using existing variation among breeds than by selecting within breeds. However, selection within breeds remains the primary method for continuing change in average genetic merit.
In 1969 a germ plasm evaluation program was started at the U.S. Meat Animal Research Center. The primary objective was to characterize biological and environmental relationships among production traits relating to growth, feed use efficiency, carcass composition and quality, reproduction, maternal traits, and carcass and meat traits. Breeds or breed crosses form an identifiable source of biological or genetic variation in production traits.
The first cycle of breed crosses (Cycle I) resulted from artificial insemination (AI) of Hereford and Angus cows by Hereford, Angus, Jersey, South Devon, Limousin, Charolais, and Simmental bulls. The Hereford and Angus cows were purchased as calves from commercial producers. A large number of sires were used in the program: 32 Hereford, 35 Angus, 33 Jersey, 27 South Devon, 20 Limousin, 26 Charolais, and 27 Simmental bulls. Hereford and Angus sires were sampled from those selected on individual performance by AI organizations for their progeny testing programs. Jersey bulls were selected at random from two commercial AI organizations, and the South Devon bulls were sampled from an importation made in 1969 by a commercial organization. Charolais, Limousin, and Simmental bulls were sampled from those available from commercial organizations. In addition, Limousin and Simmental semen was obtained from the Canada Department of Agriculture. No progeny test results were available on any of the bulls at the time they were sampled for this program.