Observations on the phosphorus requirement of cattle for growth.

Weaner cattle were fed ad libitum a diet of Stylosanthes humilis (Townsville stylo) containing 1.80 per cent nitrogen and 0.12 per cent phosphorus in the dry matter, with or without a supplement of phosphorus at the rate of 5 g/day. The feed was consumed in amounts sufficient to support gains in weight of over 0.5 kg/day during the experiment, and the supplement had no influence on voluntary feed intake, live weight gain or phosphorus concentration in samples of rib bone obtained by biopsy at the end of the experiment. It is suggested that the recomendations of the Agricultural Research Council and the National Research Council for the intake of phosphorus by young growing cattle overestimate requirements by approximately 35 per cent.