The Comparative Energy Requirements of Sheep and Cattle for Maintenance and Gain1

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Abstract
The energy requirements of sheep and cattle for maintenance and gain have been investigated, 64 sheep and 39 cattle serving as the experimental animals. The response to different levels of energy intake was measured by body weight gain and by energy retention. The data were analyzed by linear and exponential regression of energy intake, expressed as TDN, DE, and ME, on these two measures of response. Net energy requirements were also determined. Energy retention was estimated by a modification of the comparative slaughter technique. This technique was simplified by making use of the known relationships which exist among the major chemical components of the animal body. The specific gravity of the dressed animal carcass was the only measure necessary from which body composition could be estimated. The relationships necessary for estimating body composition of cattle from carcass specific gravity were available in the literature. To apply this method to sheep the necessary relationships were established from data found in the literature and by the chemical analysis of 20 sheep carcasses. The following relationships were established: All whole body values are on a wool-free empty-body basis. The estimated daily energy requirements of sheep and cattle for maintenance of energy equilibrium can be obtained in terms of the different measures of food energy by the following expressions: TDN and weight (w) are in pounds. DE, ME, and NE are in kilocalories. The partial efficiency of food utilization was found to be independent of body size. Therefore, one relationship between energy intake and energy gain will express the energy requirements of sheep and cattle. For example, an estimate of DE for any rate of energy gain in either species can be determined from the expression: where ge is gain in kilocalories. Other less complex, easier to use relationships between energy intake and energy retention or body weight gain were established from the data. These equations enable the estimation of the energy required for any rate of energy retention or weight gain in each species. In estimating energy requirements, TDN, DE, and ME can be used as the measure of food energy with equal accuracy. This is interpreted as indicating an equality between these measures of food energy for expressing the energy value of a ration. Copyright © . .