Calcium Mobilization Studies with Young Dairy Calves

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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 Ca and plasma inorganic P before, during and after injection. Rate of administration of Na2EDTA in the single injection phases of the study varied from 17.7 to 5.1 mg/kg/minute. The level to which the serum Ca is lowered is a function of the rate and amount of chelating agent injected. Oxalate-precipitable blood serum Ca reduced to tetanic levels is restored to preinjection levels within 2 hours postinjection. The response of plasma inorganic P was variable. There was considerable variation among calves in levels of oxalate-precipitable Ca at which tetany occurred. It is postulated that the rapidity with which the blood serum Ca levels was replenished indicates that calves have a large labile source of Ca. A chelating agent, Na2 EDTA), when injected intravenously combines with the blood serum Ca. The Na ion of the chelate is displaced by Ca 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 blood serum Ca, so that rate of Ca mobilization may be studied.

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