Total Body Water Estimations in Dairy Cattle using Tritiated Water

Total body water determinations were made on six dairy cows using tritiated water (TOH). Blood plasma, urine, and milk were used for these determinations, and blood plasma appears to be the most satisfactory. Body water estimates of 69.8 and 71.9% were obtained for two lactating cows, 69.0 and 67.6% for two nonlactating cows and 56.3 and 56.2% for two fat nonlactating cows. Equilibrium of intravenously dosed TOH was reached between blood plasma and rumen juice in 3 to 4 hr.