RESUMO
The aim of this study was to evaluate different treatments of postpartum subclinical hypocalcemia in dairy cows with emphasis on PTH response. Twenty four cows with subclinical hypocalcemia (Ca 1.4-2.0â¯mmol/L), out of 180 Holstein cows tested, were assigned in one of three equal groups: (1) CON received no Ca supplementation, (2) PO-Ca received 1000â¯mL of oral Ca suspension, immediately after establishing hypocalcemia, and 500â¯mL of the suspension 12â¯h after, (3) IV-Ca intravenously received 500â¯mL of Ca immediately after establishing hypocalcemia. The blood samples were taken up to 48â¯h after initial treatment for determination of Ca, iP, Mg and PTH concentrations. Urine pH was also evaluated up to 48â¯h after initial treatment. Compered to CON cows that were hypocalcemic up to the 48â¯h, Ca concentrations were significantly higher in PO-Ca up to hour 8 and IV-Ca up to hour 24. At first 2â¯h, PTH concentrations were significantly lower, compared to CON, only in IV-Ca, while at hour 4 PTH concentrations were significantly lower in both treated groups. At hours 24 and 48, PTH concentrations were significantly lower only in PO-Ca compared to CON group. Urine pH values in CON indicate alkalosis and were significantly lower both in PO-Ca and IV-Ca group, up to 12â¯h and 24â¯h respectively. In conclusion, both treatments mitigated hypocalcemia in cows, but with significantly different PTH response. Due to adequate PTH response, normocalcemia is established in CON and expected transient hypocalcemia is avoided in IV-Ca cows.