In vivo prediction of extracellular and intracellular water in cattle and sheep using thiocyanate and urea.

Abstract

Two experiments were conducted in cattle and sheep to determine the earliest time for thiocyanate equilibration with extracellular water. In Exp. 1, nine animals were infused to determine marker concentrations and sampling times. In Exp. 2, five steers were infused and then exsanguinated for tissue analyses. Thiocyanate equilibrated 22 to 31 min after infusion with a pool size equivalent to expected extracellular water. Plasma thiocyanate half-life averaged 29 h. Tissue concentrations 24 or 48 h after thiocyanate infusion were 20 to 24% of those observed in plasma for heart muscle and kidney and 6 to 8% in liver and skeletal muscle. A procedure is proposed for the in vivo estimation of empty body water (urea dilution), extracellular water (thiocyanate dilution) and, by difference, intracellular water in cattle and sheep, requiring only three blood samples, an initial sample and two samples taken 12 and 28 min after intravenous infusion of a urea-thiocyanate solution.

Quantifying body water kinetics and fecal and urinary water output from lactating Holstein dairy cows

“…Consistently, lactating cows were found to be associated with greater RCW losses than dry cows (Holter and Urban, 1992;Silanikove et al, 1997). Under thermoneutral conditions, the lactating Holstein cows in Holter and Urban (1992) Gad and Preston (1990) and Ross et al (1992) determined mean Q EC and Q IC of cattle to be 21.5 and 32.3% of live BW, respectively. Net water transfer from the intracellular to extracellular compartment (F IC,EC , Figure 1) could be related to homeostatic control of volume and thereby osmolality of extracellular fluids, primarily blood plasma.…”

Water requirements and body water distribution in Awassi sheep and Aardi goats during winter and summer seasons

“…Body water was determined simultaneously with extracellular fluid (ECF) by urea and sodium thiocyanate (NaSCN) dilution methods, respectively (Gad & Preston 1990). Five animals from each group were used for determining body water and body water compartments.…”