Stability of plasma metabolites and hormones in parturient dairy cows.

Metabolic changes that accompany the transition from parturition to lactation in dairy cows were studied. To measure these changes, plasma samples were obtained from 20 mature Holstein-Friesian dairy cows 10 days before through 10 days after parturition. They were analyzed for glucose, free fatty acids (FFA), lactic acid, ketone bodies, glucocorticoids, insulin, and growth hormone concentration. Lactic acid and glucocorticoids remained constant during the experiment, except for the day of parturition itself. In the prepartum period, changes were not detected in concentrations of hormones (glucocorticoids, insulin, and growth hormone), whereas, plasma metabolites began changing prior to parturition. Most evident were prepartum increased in FFA, ketones, and glucose. Postpartum plasma glucose concentration rapidly returned to prepartum concentrations. Plasma concentration of FFA and ketone bodies remained elevated for longer periods.