Prediction of the energy requirements for growth in beef cattle 3. Body weight and heat production in Hereford × British Friesian bulls and steers

Abstract

SUMMARY: 1. A total of 74 energy balance trials was made with five Hereford × British Friesian bulls and five steers raised intensively on a barley/protein diet to a slaughter weight of about 450 kg.2. Predicted basal metabolism (F′) was calculated for each trial by extrapolation to zero intake of measurements made on animals in positive energy balance. Logarithmic and linear equations are presented for F′ for bulls and steers throughout growth. Bulls had F′ values about 20% higher than steers.3. Values for fasting metabolism (F) in young cattle are reviewed and compared with values for F′ It is concluded that observed differences within and between different estimates of F and F′ can be attributed to the impetus for growth in young animals. Thus, at a stated body weight and intake of metabolizable energy, heat production is influenced by class and breed, bulls being higher than steers and large breeds higher than small breeds.