Stability of plasma metabolites and hormones in lactating dairy cows.

Plasma concentration stability of glucose, free fatty acids, ketone bodies, growth hormone, insulin were determined in lactating dairy cows. Concentrations of these metabolites and hormones were measured during a 36- to 48-hour period in 3 normal, mature dairy cows in the 2nd month of lactation. Samples were taken at 30-minute intervals; also, intensive sampling (every 10 minutes) was done at varying times in relation to feeding and milking. Of the 5 components measured, glucose concentration was the most stable, easiest to assay, and most reliable for use as a diagnostic aid in assessing metabolic carbohydrate disturbances in dairy cattle.