Whole body composition of heifers in relation to phosphorus status with particular reference to the skeleton

Abstract

SUMMARYThe carcass composition of phosphorus-deficient heifers of lower body weight was similar toad libitumand restricted-fed controls supplemented daily with an extra 12 g phosphorus. The skeleton of heifers fed a phosphorus deficient diet for 63 weeks contained 18·8% less ash than restricted-fed controls given an extra 12 g phosphorus daily, but not less thanad libitumfed controls. Supplements of phosphorus and energy had different effects on the weights and concentration of bone minerals in skeletal components. A phosphorus supplement increased deposition of phosphorus in head, feet and tail, limbs and vertebrae and increased phosphorus concentration in head, feet and tail, vertebrae, ribs 1–5 and ribs 10–13. Extra energy intake slightly increased phosphorus accretion only in ribs 6–9 but had no effect on its concentration in this and other skeletal components. Only one (40 weeks) of the six biopsy samples taken from the cortex of the 11th and 12th ribs during the course of the experiment reflected the effect of uncomplicated phosphorus deficiency. No treatment differences were found in biopsy samples taken at slaughter in spite of differences in rib 10–13 analyses. The implications of this are discussed as they relate to the use of this method to monitor the phosphorus status of cattle.