Date of this Version
It is estimated that today about 70 percent of the calves narketed from beef cattle herds in the U.S. are crossbred and hat between 50 and 60 percent of the cows are crossbred. This represents a major shift to crossbreeding from the straight-breeding programs which prevailed in the 1950's and early 1960's. This trend has been influenced by research demonstrating the favorable effects of heterosis and other advantages of crossbreeding. Also, increased use of feed grains in growing-finishing diets caused fatter carcasses contributing to increased consumer demand for leaner beef, which stimulated interest in breeds with greater potential for lean tissue growth and less fat. As a result, a large number of breeds, introduced from Europe via quarantine facilities in Canada, became available to North American beef producers. Interest in the newly Introduced breeds and in other breeds already available coincided with the establishment and development of the Roman L. Hruska U.S. Meat Animal Research Center (MARC) in the late 1960's. The Germ Plasm Evaluation (GPE) Program was initiated in 1969 at MARC to characterize a broad range of biological types of cattle as represented by breeds that differed widely in genetic potential for milk production, growth rate, carcass composition, and mature size. The purpose of this paper will be to review results from the GPE Program for reproduction and maternal characteristics of first cross (F1) cows.