Ionized calcium in calf serum: relation to total serum calcium, albumin, total protein and pH

Serum ionized calcium, total calcium, albumin, total protein and pH were determined in 340 female Italian Friesian calves, aged from 1 day to 6 months. Analyses of data from calves divided into 7 age groups showed only occasional correlations between Ca++ and the other parameters. For pooled values for the calves aged 1-6 months, there were significant positive correlations between ionized and total calcium and between total calcium and albumin, and a negative correlation between ionized calcium and serum pH. However, the correlation coefficients were too low to be usable for prediction of the levels of ionized calcium from the levels of total calcium or from the other parameters. When it is essential to evaluate the calcium status of a calf, direct measurement of ionized calcium must be done.