The usefulness of faecal phosphorus and nitrogen in interpreting differences in live-mass gain and the response to P supplementation in grazing cattle in arid regions.

The average daily gains of heifers and oxen on commercial and experimental farms in Namibia were used to indicate production differences in several areas and at different rates of phosphorus and protein supplementation. Faecal concentrations of phosphorus and nitrogen were used to indicate concentrations of these nutrients in grazing. Areas with high concentrations of nitrogen in faeces proved to support high levels of average daily gain. Animals responded positively to phosphorus supplementation only when faecal nitrogen concentrations were above 12 g/kg DM. Nitrogen concentrations in faeces were directly related to average daily gain of heifers, but protein supplementation did not have a significantly positive effect on average daily gain.