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Phosphorus and calcium metabolism in growing calves with special emphasis on phosphorus homoeostasis: 3. Studies of the effect of continuous intravenous infusion of different levels of phosphorus in ruminating calves receiving adequate dietary phosphorus

Published online by Cambridge University Press:  27 March 2009

J. Challa
Affiliation:
AFRC Institute for Grassland and Animal Production, Hurley, Maidenhead, Berkshire, SL6 5LR
G. D. Braithwaite
Affiliation:
AFRC Institute for Grassland and Animal Production, Hurley, Maidenhead, Berkshire, SL6 5LR

Summary

Calves were fed continuously at 4 h intervals an adequate-P diet and were infused intravenously with a solution of phosphate supplying either 0, 3, 6 or 9 g P/day in a 4 x 4 latin-square design experiment. Once steady-state conditions were achieved, rates of flow of P at the reticulum, serum P and Ca concentrations, and urinary excretion rates of P and Ca were measured.

The concentration of serum P increased significantly with increased intravenous infusion of P as also did the salivary P secretion. Results suggest that it is the serum P concentration that regulates the secretion of P through saliva. Urinary P excretion, which was low in the control group, increased significantly with increased intravenous loading of P. Substantial urinary P excretion occurred, however, only when the serum P concentration exceeded 2·30 mmol/1, which is probably the renal threshold for P. The serum Ca concentration was unaffected by the intravenous infusion of P and urinary Ca excretion remained negligible on all treatments.

Type
Research Article
Copyright
Copyright © Cambridge University Press 1988

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