Date of this Version
Since the introduction of new germ plasm resources into the U.S. beginning in the early 1960's, the influence of biological types on various aspects of beef production have been evaluated extensively. Traits studied include preweaning calf performance, postweaning growth and feed efficiency, carcass characteristics, puberty and other reproductive characteristics, and milk production, to name a few. In general, however, most of the research efforts have concentrated on the areas involving the growing animal and/or its carcass characteristics. That is, output characteristics of the various biological types of cattle have been of primary interest to researchers. Much less effort has been expended to quantify the impact various biological types of cattle may have on input components of beef production. There has been, in particular, a dearth of information regarding the influence of biological type on the feed requirements of mature cows, even though various researchers have noted that the feed required to replenish and maintain the cow herd constitutes a major portion (65 to 75%) of the feed resources required for beef production. Differences among biological types in the feed required to maintain the cow herd may have a substantial impact on the efficiency of beef production. Thus, in this report, we will attempt to summarize our data relative to the effect of biological type on feed energy requirements of mature cows.