Response of Some Blood Constituents to Infusions of Disodium Ethylenediamine Tetraacetate in Intact Cattle

Lactating and dry cows were intravenously infused with a 10% aqueous solution of disodiunl ethylenediamine tetraacetate.Infusion was at a constant rate until tetany developed.Blood samples were drawn before infusion and at specified times during and post-infusion.The serum was analyzed for calcium and inorganic phosphorus.Total leucocytes were counted.Smears were made from each blood sample and stained for differential counts.The means are from 19 observations (13 for the leucocytes).The serum calcium mean preinfusion level was 10.79 mg per 100 ml, decreasing to a mean of 4.9 rag per 100 ml at tetany.Tetany occurred at a mean of 163 min from the beginning of infusion.At 24-hour post-infusion the mean was 10.11 mg per 100 ml.The mean preinfusion level of phosphorus was 6.10 mg per 100 ml and the mean level at tetaay was 4.28 mg per 100 ml.The low mean of phosphorus, 3.89 mg per 100 ml, occurred 90 min post-tetany.The preinfusion levels of phosphorus were practically attained by 12-hr post-infusion.A slight decrease followed by a steady increase to a peak at 8-hr post-infusion occurred in the total ~VBC count.There was a gradual decrease in number from the peak to the 24-hr sample.A sharp diminution in the per cent of lymphocytes occurring simultaneously with a marked increase in the per cent of neutrophils caused a crossing over in the percentages of these types of cells by the 3-hr post-infusion sampling.Normal ratios had not been attained by 24-hr post-infusion.Calcium is of nutritional importance in both young and old.It is of special importance to the lactating animal because of the high calcium content of milk.Milk of average composition from the dairy cow contains 0.5 g calcium per pound (1).This takes on staggering proportions when one considers that milk production may increase in a cow from zero to 60 lb daily in 15 to 20 days.Negative calcium balances occur in lactating women, rats, and cows, even when calcium intake is abundant.Bone serves as a reserve supply of calcium and as much as 18% of the skeletal calcium is depleted during lactation (7).Regulation and maintenance of calcium in the body fluids is the function of the parathyroid glands.There have been numerous postulations on the mechanisms by which this feat is