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 to ad 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 than ad libitum fed 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.

Effects of dietary phosphorus and nitrogen deficiencies on the intake, growth and metabolism of lambs

“…As the neutron activation technique measures the total amount of P in a length of bone, changes in cortical thickness are taken into account. Differences in the degree of demineralization of the cortexes of rib bones and long bones have been observed by Hill (1962) and Hoey et al (1982). Use of the neutron activation technique emphasises the underestimation of the deossification of the metatarsal bone using mineral analyses of the bone cortex (Ternouth et al 1980).…”

Factors affecting the faecal P status of lactating beef cattle in Northern Australia

“…Subclinical P deficiency, or aphosphorosis, presents typically as lower live weight gains due to a reduction in skeletal growth, which in turn limits the growth of soft tissues i.e. muscle (Field et al, 1975;Hoey et al, 1982;Read et al, 1986a;Winter, 1988;Coates, 1995;Miller et al, 1996;White et al, 1996), and reduced feed intake and feed conversion efficiency due to a reduction in the efficacy and efficiency of microbial digestion. This reduction in intake and feed conversion efficiency is difficult to measure/observe in extensively grazed ruminants (Little, 1980;Gartner et al, 1982;Milton and Ternouth, 1985;Read et al, 1986a;Jones, 1990;Ternouth and Sevilla, 1990;Coates, 1995;Bortolussi et al, 1996;Ternouth et al, 1996), Other symptoms of subclinical aphosphorosis include reduced reproductive performance (Theiler et al, 1928;Read et al, 1986a;Ternouth, 1990), prolonged lactational anoestrus , lower milk yield (Read et al, 1986a;Knowlton and Herbein, 2002), lower branding percentages (Ternouth, 1990), lower weaning weights (Read et al, 1986a), and a tendency for broken bones during normal husbandry practices from excessive resorption of bone (Cohen, 1973a;Cohen, 1973b;Williams et al, 1990;Williams et al, 1991;De Brouwer et al, 2000) .…”

“…There is still limited experimental data on the repletion of bone P in breeding cows. Hoey et al (1982) studied two groups of heifers given a low P and a high P diet (difference 12g P/d). The difference in bone P between the two groups at the end of a repletion phase was 535g P (approx.…”

“…Little (1972) described a method that surgically removes a small disc (biopsy) from the 11 th or 12 th rib, usually 20 cm from the spine. This method has consistently demonstrated significant differences between cattle fed different dietary P intakes, and so this has become the main method used for measuring P status (Little, 1972;Little and Shaw, 1979;Hoey et al, 1982;Read et al, 1986b;Ternouth, 1990;de Waal and Koekemoer, 1997;Keene et al, 2004). Units of measure have developed and changed over time.…”

“…The cancellous bones (ribs) turnover Ca and P much more readily than compact (limb) bones. For example, Hoey et al (1982) fed heifers for 63 weeks on an adequate or P deficient diet and took biopsies at intervals throughout the project. The P contents measured in the ribs differed from other bone P contents and from the P content of the total skeleton after slaughter.…”