Phosphate deficiency in cattle on the Sepik Plains, Papua New Guinea.

Two large scale grazing experiments were carried out, each for 3 years, to define the need for phosphorus supplementation. After 15 months without phosphorus heifers subsequently supplemented with copper or cobalt only grew 0 . 147 kg/day over 15 months indicating apparent stunting. They calved later than continuously supplemented animals, weighed less and weaned smaller calves. Ad libitum supplementation with phosphorus resulted in faster growth of non-pregnant and pregnant heifers and their calves and more rapid breeding than 2 limited supplementation treatments while unsupplemented animals performed worst. In all treatment groups the maximum weight loss by lactating heifers was one-third of pre-calving weight. Heifers receiving limited supplementation had the highest mortality while unsupplemented heifers dried off earlier. Ad libitum phosphorus supplementation was the optimum for animal and financial performance.