1-ALPHA-HYDROXYVITAMIN-D3 PLUS 25-HYDROXYVITAMIN-D3 REDUCES PARTURIENT PARESIS IN DAIRY-COWS FED HIGH DIETARY CALCIUM

The effectiveness of a combination of 1-alpha-hydroxyvitamin D3 and 25-hydroxyvitamin D3 for reducing incidence of parturient paresis in aged Holstein cows was tested. Intramuscular injection of .5 mg of 1-alpha-hydroxyvitamin D3 plus 4 mg of 25-hydroxyvitamin D3 increased plasma 1,25-dihydroxyvitamin D concentrations through parturition. Treatment with 1-alpha-hydroxyvitamin D3 plus 25-hydroxyvitamin D3 raised prepartum serum Ca approximately 2 mg/dl and prepartum serum P approximately 4 to 5 mg/dl higher than untreated controls. Both treated and control cows had approximately a 2-mg/dl decrease in serum Ca following parturition. The prep diet of alfalfa silage and hay was supplemented with a grain mixture supplying 100 g of Ca/d from ground limestone. Under these dietary conditions, incidence of parturient paresis was reduced from 33 to 8%. In a separate experiment, treatment with 1-alpha-hydroxyvitamin D3 plus 25-hydroxyvitamin D3 did not reduce incidence of parturient paresis when cows consumed mixed diets of different feedstuff composition. Further experiments are required to determine specifically the factor or factors responsible for the difference in response to active vitamin D compound administration between the two experiments. Prepartum dietary Ca intake may be one such factor.