A COMPARISON OF SUPPLEMENTAL FORMS OF PHOSPHORUS

Four yearling Holsteins were utilized in a 4 × 4 latin square designed experiment to assess the availability of phosphorus in four chemical forms: dicalcium phosphate; monocalcium phosphate; monoammonium phosphate and monosodium phosphate. The chemical form of supplement had no apparent effect on plasma levels of phosphorus, calcium or magnesium or on the fecal excretion of phosphorus. Dry matter intake and digestibility of dry matter were not influenced by chemical form of supplement but digestibility of the acid detergent fiber fraction was higher, 59.2 vs. 56.5, for monosodium phosphate compared with monoammonium phosphate. The molar proportion of propionate in the rumen fluid was significantly greater (P < 0.05) when monosodium phosphate was fed compared with the feeding of either monocalcium phosphate or monoammonium phosphate. Under the conditions of this experiment it was concluded that there were no differences in availability of phosphorus among the four chemical forms studied.