Short communication: Estimation of plasma osmolality from plasma electrolytes, glucose, and urea in calves

Plasma osmolality estimated from plasma concentrations of Na+, Cl-, K+, glu cose, and urea was compared with measured osmolality in preweaned Holstein calves. When calves (n = 5) were fed only milk replacer after fasting for 2 4 h, measured osmolality fluctuated almost in parallel with estimated osmol ality during the 8-h period after feeding, although estimated values mere a bout 90% of measured values. When calves (n = 5) were fed only calf starter after fasting for more than 16 h, measured osmolality did not parallel the estimated osmolality during the 8-h period after feeding. Some factors dep ressed measured osmolality in the first 2 h.