A System for Expressing Net Energy Requirements and Feed Values for Growing and Finishing Beef Cattle

Abstract

A proposed system is presented for expressing net energy requirements and feed values for growing and finishing beef cattle. The system uses one expression, NE_m, to represent the net energy requirement and the net energy content of the feed when used for maintenance and a second expression, NE_g, for the net energy used for production of weight gain. Data from comparative slaughter trials indicate the NE_m requirement for both steers and heifers is equal to approximately 0.077 megcal. per unit of metabolic body size (W^0-7_kg.). The energy deposited in the weight gain of steers (the NE_g requirement) is represented by the equation NE_g=52.72g+6.84g² where NE_g is the kcal. of energy deposited per day per unit of W^0-75_kg. and g is the daily empty weight gain in kg. The equation for heifers is NE_g= 56.03g+12.65g². It was shown that heifers deposit more energy per unit of weight gain than do steers and that the difference is larger at higher rates of gain. Data are presented demonstrating that the proposed system is adaptable to practice and that it overcomes the common criticisms that net energy values do not apply under maintenance conditions and vary with feed intake. Copyright © 1968. American Society of Animal Science . Copyright 1968 by American Society of Animal Science