Growth in Beagles: Changes in Body Weight, Plasma Volume, and Venous Hematocrit

Abstract

Extract: Body weight, plasma volume, and venous hematocrit of 12− to 18-hr-old beagles were 0.239 \pm 0.009 kg, 52.5 \pm 1.14 ml/kg, and 48.7 \pm 1.72%, respectively. Over the next 24 hr total plasma volume increased by 31% and body weight by only 8%. During the 1-year period after birth the plasma volume (milliliters per kilogram) changed abruptly four times, and each change was followed by stable periods of varying length. The plasma volume decreased significantly between weeks 1 and 2, weeks 6 and 7, and months 3 and 4; and, finally, it increased significantly between months 5 and 6. The venous hematocrit declined during the first 6 weeks of life, then gradually increased up to month 6. Body weight, plasma volume, and venous hematocrit did not change significantly from months 6–12. Plasma volume (milliliters per kilogram) for 6− to 12-month-old beagles was 44.3, significantly less than that of the newborn.Speculation: These data suggest the need to explore mechanisms concerned with the several abrupt changes in the plasma volume that occurred during growth of the beagle and in the mechanisms involved in the marked increase in plasma volume with no reduction in venous hematocrit on day 1.