The responses of goats to the experimental induction of hypocalcaemia with cation-exchange columns.

1. Ionic calcium was selectively removed from the circulating blood of three anaesthetized goats by means of columns of cation-exchange resin. Concentrations of other ions were not directly affected by the column.2. A calcium extraction rate of 0.35 m-equiv/min caused a fall in plasma total calcium of up to 40% in 35 min. Plasma calcium concentration returned to normal within 2 hr of the end of calcium removal.3. Mobilization rates reached a maximum between 15 and 20 min after calcium removal commenced, declining rapidly after it had stopped.4. Removal of calcium by EDTA infusion results in a similar calcium mobilization pattern to that produced by Ca removal by ion-exchange.5. A smaller variation appears to exist between goats in maximum calcium mobilization rates than in maximum phosphorus mobilization rates and goats may be able to mobilize phosphorus relatively faster than calcium.