Time series cross-correlation analysis of postparturient relationships among serum metabolites and yield variables in Holstein cows.

Time series cross-correlation analysis was used to determine relationships among serum beta-hydroxybutyrate, glucose, FFA, cholesterol, milk yield, DMI, and estimated net energy balance for 42 d postpartum for 14 multiparous cows. Milk yield was positively associated with beta-hydroxybutyrate concentrations on the same day, and milk yield was a primary determinant of metabolic change. Dry matter intake was negatively correlated with beta-hydroxybutyrate concentrations 3 d later and on the same day. The data supported in vitro studies showing that FFA are positively associated with beta-hydroxybutyrate production, showed that glucose concentrations are negatively cross-correlated with beta-hydroxybutyrate concentrations, and found that estimated net energy balance is negatively cross-correlated with beta-hydroxybutyrate. Analyses suggested that serum glucose and cholesterol concentrations significantly decreased with increased milk yield; analyses also suggested that elevated beta-hydroxybutyrate concentrations were associated with decreases in milk yield 6 d later. beta-Hydroxybutyrate and FFA concentrations 3 to 9 d before parturition were positively related to cholesterol concentrations, and relationships were positive between estimated net energy balance and cholesterol, suggesting that cholesterol concentrations increased as precursors for cholesterol synthesis were available. Time series cross-correlation analysis was a useful tool in examining relationships among variables when repeated samples were obtained from the same individuals.