Oral 1,25-dihydroxyvitamin D3 in prevention of milk fever.

The effect of daily oral doses of 1,25-dihydroxy vitamin D (1,25-(OH)D) on plasma mineral concentrations and incidence of milk fever was tested in 39 aged cows. Three dose levels of 1,25-(OH)D (0, 100 and 200 µg/d) were compared in cows supplemented with 100 g Ca/d (250 g CaCO) and in cows receiving no Ca supplement. 1,25-(OH)D treatments were given from day 5 before expected calving (day –5) until the day after calving (Calving = day 0). Expected minima in Ca concentrations in plasma were seen on day 1 in placebo treated cows, while Ca concentrations in 1,25-(OH)D treated cows were normal or increased in the period from start of treatment until day 3–5. In the parturient period (day –1 to +2) 1 of 21 treated cows developed milk fever, as compared to 4 of 18 untreated. A pronounced hypocalcaemia developed, however, in the 1,25-(OH)D treated cows from day 3 to 5 onwards, culminating day 8–11 with 7 cases of milk fever. Ca supplements reduced the development of hypocalcaemia in the 1,25-(OH)D treated cows, but could not completely prevent the occurrence of milk fever.