Submitted to: Conference Proceedings of Canadian Society of Animal Science
Publication Type: Proceedings
Publication Acceptance Date: 5/1/2003
Publication Date: 6/10/2003
Citation: FERRELL, C.L. 2003. ENERGY PARTITIONING IN RUMINANTS AS RELATED TO FEED INTAKE. CONFERENCE PROCEEDINGS OF THE CANADIAN SOCIETY OF ANIMAL SCIENCE. 10 PP. SASKATOON, SASKATCHEWAN, CANADA.
Technical Abstract: A classical partitioning of dietary energy into fecal, urinary, gaseous, heat, and retained energy is presented. Evidence shows that fecal and heat constitute the largest losses of consumed energy. Considerable variation in fecal energy losses exists due to characteristics of dietary ingredients and level of intake. Some evidence also exists to indicate variation among animals in their ability to digest as well as to consume feed. In particular, increased fecal losses with increased intake and differences in site of digestion due to increased intake or differences among animals may have direct and important effects on quantity and quality of substrates available to the animal. Numerous data are available indicating variation among animals in heat losses due to body size, age, thermal environment, activity, feed intake and digestion, and metabolism. Several components of those losses are described. Feed energy intake minus the sum of energy losses results in a nonlinear response of retained energy to energy intake. Thus, incremental increases in feed intake are expected to result in incrementally less increase in retained energy. Opportunities for improvement in efficiency of energy utilization certainly exist. It would seem that more opportunities exist to reduce energy losses than to increase retained energy. Certain contributors to energy expenditures, such as voluntary activity, may be relatively easily modified to reduce energy losses. Although variation exists in numerous other components of animal digestion and metabolism, those components exist as parts of highly regulated, integrated systems. Progress in reduction of energy losses will likely require incremental changes in systems, rather than in major genes.