|Oltjen, James - UNIV CALIFORNIA, DAVIS|
Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: April 14, 2008
Publication Date: July 23, 2008
Citation: Ferrell, C.L., Oltjen, J.W. 2008. Discovery and application of energetic principles to feeding systems for beef cattle [abstract]. Journal of Animal Science. 86 (E-Supplement 2):611. Technical Abstract: Development of nutritional energetics can be traced to the eras of Leonardo da Vinci (1452-1519) and Lavoisier (1743-1794), who discovered the basic concepts. Lavoisier established relationships among O2 use, CO2 production and heat production (HP). The laws of thermodynamics were discovered in the 1840’s. They state that 1) energy can be neither created nor destroyed, but can be transformed from one form to another, 2) all forms of energy can be quantitatively converted to heat, and 3) heat loss in a chemical reaction is independent of path. These laws enabled the fundamental entity ME = RE + HP to be established. Objectives became 1) establish relationships between gas exchange and HP, 2) devise basis for evaluation of foods that could be related to energy expenditures, and 3) establish causes of energy expenditures. The bomb calorimeter was invented, allowing determination of the energy contents of organic compounds. Concepts and equipment for animal calorimetry were developed. Early systems for evaluation of foods for their value in supplying animal energy needs were based in measurements of ME and HP determined from calorimetry. Work in these areas arguably culminated in 1965 with the Brouwer equation for calculation of HP from O2 use and CO2, CH4, and N excretion. For many years, primary efforts were devoted to measurement of ME and HP, with RE a secondary consideration. The California Net Energy System, developed for finishing beef cattle, was the first net energy system based on RE as determined by comparative slaughter and was the first to use two net energy values (NEm and NEg) to describe feed and animal requirements. This system has been broadened conceptually to encompass energy requirements during the life cycle of beef cattle. This system remains useful, but has limited capacity, due to its empirical and static nature, to capture the dynamics of energy utilization by diverse animals as they respond to changing environmental conditions.