Many rangeland regions have low phosphorus soils so that the pastures are deficient in phosphorus for grazing cattle. Cows in early lactation are particularly at risk of deficiency due to their high nutritional requirements. An experiment examined the responses of mature lactating beef cows to severe dietary phosphorus deficiency. During early lactation cows were able to mobilise substantial amounts of minerals from bone to alleviate dietary phosphorus deficiency and maintain milk production, albeit with reduced voluntary feed intake and marked liveweight loss.