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Calcium Mobilization Studies with Young Dairy Calves¹

Department of Dairy Husbandry, University of Wisconsin, Madison

ABSTRACT

Young dairy bull calves were injected intravenously with solutions of the disodium salt of ethylenediaminetetraacetic acid (Na₂EDTA) at various rates and amounts. The effect of the injections was ascertained by analyses of the oxalate-precipitable blood serum calcium and plasma inorganic phosphorus before, during, and after injection. The rate of administration of Na₂EDTA in the single injection phases of the study varied from 17.7 to 5.1 mg/kg/min. The level to which the serum calcium is lowered is a function of the rate and amount of chelating agent injected. Oxalate-precipitable blood serum calcium reduced to tetanic levels is restored to preinjection levels within 2 hr. postinjection. The response of plasma inorganic phosphorus was variable. There was considerable variation among calves in the levels of oxalate-precipitable calcium at which tetany occurred. It is postulated that the rapidity with which the blood serum calcium levels was replenished indicates that calves have a large labile source of calcium. A chelating agent, the disodium salt of ethylenediaminetetraacetic acid (Na₂EDTA), when injected intravenously combines with the blood serum calcium. The sodium ion of the chelate is displaced by calcium which forms a soluble, non-ionizable, physiologically unavailable complex with EDTA that is not precipitated with oxalate. EDTA thus provides a tool for immediate lowering of the blood serum calcium, so that the rate of mobilization of calcium may be studied.

¹ Published with the approval of the Director of the Agricultural Experiment Station.