The course of selected bone resorption marker concentrations in response to short-term hypocalcemia experimentally induced with disodium EDTA infusions in dairy cows

The collagen metabolites hydroxyproline (HYP), deoxypyridinoline (DPD), and the carboxyterminal telopeptide of type I collagen (ICTP) are suitable mar kers for bone resorption in humans and several animal species. The purpose of this study was to describe the course of bone resorption markers during short-term hypocalcemia induced with disodium ethylenediaminetetraacetic ac id (Na(2)EDTA) and to investigate whether bone resorption is increased in d airy cows under these conditions. EDTA infusions have been used as a model for periparturient paresis in dairy cows and to estimate the calcium mobili zation rate from body reserves in ruminants. In this study, hypocalcemia wa s induced by means of a 5% Na(2)EDTA infusion (0.55 mg/kg/min Na(2)EDTA for 5 h = total dose of 100.6 g). Two experiments were conducted: (1) Six 4-11 years-old Brown Swiss cows were infused intravenously with EDTA for 5 h. B lood and urine samples were taken repeatedly from 1 day before until 10 day s after infusion. (2) Towards the end of the lactation, the experiment was repeated with the same animals after a 14-day-period of feeding a low calci um diet (26 g/animal per day). The EDTA-infusion induced hypocalcemia and h ypophosphatemia. The HYP-, DPD- and ICTP-concentration remained mainly unaf fected during both infusions. Only DPD showed an increase during infusion a nd HYP an increase 2 days after the infusion. In conclusion, the EDTA infus ion had little effect on the concentrations of the measured bone markers, w hich may be due to the fact that the serum calcium pool was refilled by inc reased absorption of Ca via the gastrointestinal tract. From these results, it can be concluded that bone resorption was not: influenced by EDTA infus ion.