Date of this Version
Presented at Range Beef Cow Symposium XXII, November 29, 30, and December 1, 2011, Mitchell, Nebraska. Sponsored by Cooperative Extension Services and the Animal Science Departments of the University of Wyoming, Colorado State University, South Dakota State University, and the University of Nebraska–Lincoln.
Improving cow herd efficiency is critical because approximately 70% of the feed inputs required to produce a slaughter animal are used for maintenance, the majority of which is utilized by the dam (Williams and Jenkins, 2006). To date, much of the efforts to improve efficiency in cattle have focused on different measures of feed efficiency (variations in amount of feed consumed and rate of weight gain) determined during the growing phase. While this approach provides pertinent information concerning efficiency during the growing phase, the relationship to cow efficiency remains to be determined. When considering the usefulness of feed efficiency as an indicator of cow efficiency, it is important to assess the specific approach used to determine feed efficiency and compare the input and outputs that contribute to efficiency during the different phases of production. In cows, the most critical factor influencing output component of efficiency is lifetime reproductive rate, not weight gain. Lifetime reproductive rate is a cumulative process and may require years to establish which has limited efforts to identify processes contributing to variation in output among individual animals. Furthermore, nutrition and management components of cow-calf production in range environments are more complex and subject to greater seasonal and annual variation than in confined settings where harvested feeds of relatively homogeneous quality are typical of the feedlot phase of production, and while technology exists to measure feed intake of individual animals in a feedlot setting, methods are not available for quantifying feed intake under grazing conditions.
The wide variations in environmental and management conditions existing in cow-calf production contribute to the challenge of establishing genetic components of efficiency universal for all cows and likely impart the need to match different genetic types to different production environments. Matching cow type to production environment is becoming increasingly more important due to rising costs of providing supplement feed when production potential exceeds nutrient availability. Increasing cost associated with providing supplemental feed to the cow herd may lead to greater distinctions between biological and economic efficiency in the cow-calf phase compared to other segments. For example, cows that consume more calories during the vegetation growing season and gain sufficient weight to exist on less harvested feed inputs during winter may require less total economic input than cows with greater potential for feed conversion that consume less during the growing season, but require more calories from harvested feed later. Efficiency of beef cattle production requires a balance between amount and cost of nutritional inputs with prolonged optimal output. A provocative question to consider is whether traditional approaches of providing sufficient feed to a herd of cows to achieve a relatively high rate of reproduction results in improved efficiency or not? Is this analogous to selecting a type of cattle and managing the environment to sustain the type?