Figure 1: Plasma ionised calcium in cows fed basic ration then infused intravenously with EDTA from time zero onwards. The last blood sample was taken at recumbency.

Mentions: An initial fast drop was observed during the first 20 min of infusion followed by a constant drop until recumbency in the control cows as well as the anion supplemented cows (Figs. 1a and 2). The length of infusion period until recumbency varied between cows and there was no correlation between the pre-infusion concentration of calcium and the total amount of EDTA infused until recumbency (r2 = 0.024).

Mellau LS, Jørgensen RJ, Enemark JM - Acta Vet. Scand. (2001)

Bottom Line: Methods previously used were not described in detail and results obtained by monitoring total and free ionic calcium were not comparable due to differences in sampling and analysis.Pre-infusion [Ca2+] between tests does not correlate with the amount of EDTA required to induce involuntary recumbence.The standardized infusion technique might be useful in future experimental studies.

Affiliation: Cattle Production Medicine Research Group, Clinical Department, Large Animal Medicine, Royal Veterinary and Agricultural University, Frederiksberg, Denmark. leme@suanet.ac.tz

Abstract: The intravenous Na2EDTA infusion technique allows effective specific chelation of circulating Ca2+ leading to a progressive hypocalcaemia. Methods previously used were not described in detail and results obtained by monitoring total and free ionic calcium were not comparable due to differences in sampling and analysis. This paper describes a standardized EDTA infusion technique that allowed comparison of the response of calcium, phosphorus and magnesium between 2 groups of experimental cows. The concentration of the Na2EDTA solution was 0.134 mol/l and the flow rate was standardized at 1.2 ml/kg per hour. Involuntary recumbency occurred when ionised calcium dropped to 0.39-0.52 mmol/l due to chelation. An initial fast drop of ionized calcium was observed during the first 20 min of infusion followed by a fluctuation leading to a further drop until recumbency. Pre-infusion [Ca2+] between tests does not correlate with the amount of EDTA required to induce involuntary recumbence. Total calcium concentration measured by atomic absorption remained almost constant during the first 100 min of infusion but declined gradually when the infusion was prolonged. The concentration of inorganic phosphate declined gradually in a fluctuating manner until recumbency. Magnesium concentration remained constant during infusion. Such electrolyte responses during infusion were comparable to those in spontaneous milk fever. The standardized infusion technique might be useful in future experimental studies.