INFLUENCE OF PREVENTION OF PARTURIENT PAR ESIS BY ADMINISTRATION OF 1-ALPHA-HYDROXYCHOLECALCIFEROL ON THE CONCENTRATIONS OF IONIZED CALCIUMIN BLOOD AND FURTHER MINERALS IN BLOOD-PLASMA IN THE DAIRY-COW

The concentrations of ionized calcium (Ca(i)) in blood and of total ca lcium (Ca(t)), inorganic phosphorus (P(i)) and magnesium (Mg) in blood plasma were determined in the peripartal period in 23 dairy cows of t he breed ''Schwarzbuntes Milchrind'' from the fourth lactation onward with negative history of parturient paresis and in 18 cows which fell ill at the occasion of the last parturition. To the last-mentioned ani mals were injected intramuscularly 70 mug (n - 10), 210 mug1 alpha-hyd roxycholecalciferol (1 alpha-OHD3) alone or together with 2 mg 25-hydr oxycholecalciferol (25-OHD3)(n = 4) or 420 mug1 alpha-OHD3 (n = 4) 2 t o 3 days before the calculated time of parturition. Measurement of Ca( i) was made with an ionselective electrode. In all groups the administ ration of 1 alpha-OHD3 resulted in a significant increase in the plasm a concentrations of Ca(t), Ca(i) and P(i), whereas the level of Mg dec reased. After administration of 420 mug 1 alpha-OHD3 significantly hig her concentrations of Ca(t), Ca(i) and P(i) were measured until 24 h a fter parturition compared to untreated control animals. In cows receiv ing lower doses of 1 alpha-OHD3, at birth significantly smaller concen trations of Cat (after 70 and 210 mug 1 alpha-OHD3), Ca(i) (after 210 mug 1 alpha-OH D3) and of P(i) (after 70 mug 1 alpha-OHD3) compared to the cows to which 420 mug 1 alpha-OHD3 were injected, were measured. Thereby, the portion of Ca(i) from Ca(t) was not altered. Only in 3 co ntrol animals which fell ill, but not in those 3 cows suffering from p aresis puerperalis after injection of 70 mug 1 alpha-OHD3, the concent rations of Ca(i) decresed to a greater extent compared to Ca(i). Taken together it can be concluded that by prepartal administration of 70 m ug1 alpha-OHD3, even if the behaviour of the plasma concentration of C a(i) is taken into consideration, it is not possible to prevent peripa rtal hypocalcaemia and parturient paresis with sufficient safety.