Plasma Estradiol in Holstein and Beef Cows During the Periparturient Period

Plasma estradiol, measured by radioimmunoassay, was compared in Holstein and beef cows during the periparturient period.A disposable Celite column was used for separation of estrogens.The antibody-estrogen complex was separated by charcoal and eentrifugation.Circulating plasma estradiol was higher in 11 Holstein than in 9 beef cows prior to parturition.For Holstein cows, among nonsignificant differences, highest mean concentrations were 580 pg/ml on the day before parturition and 440 pg/ml on the day of pm'ttmtion.Beef cows reached a peak of 538 pg/m] on the day of parturition.Concentrations rapidly and similarly decreased in both groups following parturition.