Relative Growth Rate of Beef Cattle Expressed Using Factors Related to Feed Intake, Maintenance Requirements and Feed Efficiency

This study was conducted to present a method for growth analysis of beef cattle using factors related to feed intake, maintenance requirements and feed efficiency. The following equation was taken up for growth analysis, 1/W · dW/dt = (1/W^0.75 · dI/dt) · W^0.75/W · dW/dI, where W = body weight, t = day, W^0.75 = metabolic body size, I = cumulative intake of metabolizable energy, (1/W) • (dW/dt) = relative growth rate [RGR], (1/W^0.75) • (dI/dt) = daily intake of metabolizable energy per unit metabolic body size [DIM], W^0.75/W = metabolic body size ratio [MBS ratio] or maintenance requirements index [MR index], dW/dI = efficiency of metabolizable energy for gain in body weight [EEG]. Mean value over the interval t₁ to t₂ was calculated for each of RGR, DIM, MBS ratio or MR index, and EEG when applied to feeding and growth data. An application of this analytical method to Japanese Black Cattle whose feeding and growth data were cited from Japanese Feeding Standard (1995) showed that RGR was controlled by DIM, MBS ratio or MR index, and EEG, in beef cattle weighing 300 kg to 500 kg. A feature of this method was that it might account for how MR index was involved in the growth analysis of beef cattle.