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 be ef cattle using factors related to feed intake, maintenance requiremen ts and feed efficiency. The following equation was taken up for growth analysis, 1/W1/W . dW/dt = (1/W-0.75 . dl/dt) . W-0.75/W . dW/dl, whe re W = body weight, t = day, W-0.75 = metabolic body size, I = cumulat ive intake of metabolizable energy, (1/W) . (dW/dt) = relative growth rate [RGR], (1/W-0.75) . (dl/dt) = daily intake of metabolizable energ y per unit metabolic body size [DIM], W-0.75/W = metabolic body size r atio [MBS ratio] or maintenance requirements index [MR index], dW/dI = efficiency of metabolizable energy for gain in body weight [EEG]. Mea n value over the interval t(1) to t(2) was calculated for each of RGR, DIM, MBS ratio or MR index, and EEG when applied to feeding and growt h data. An application of this analytical method to Japanese Black Cat tle whose feeding and growth data were cited from Japanese Feeding Sta ndard (1995) showed that (RGR) over bar was controlled by (DIM) over b ar, <(MBS ratio)over bar> ratio or <(MR index)over bar>, and (EEG) ove r bar, in beef cattle weighing 300 kg to 500 kg. A feature of this met hod was that it might account for how MR index was involved in the gro wth analysis of beef cattle.