Blood volume and rate of growth in Standardbred foals

Blood volume and parameters of body size were studied in 45 Standardbred foals during their first 400 days of life. Bodily dimensions, including body weight (bwt), depth of chest, girth and length (distance from point of shoulder to caudal aspect of croup), increased curvilinearly with age. There was a much faster growth rate noted for the first 100 days of life. Bwt could be predicted from girth and length much more precisely than from age alone. The total blood volume increased proportionately with age and, consequently, the plasma and red cell volumes as functions of bwt were high at birth (mean 93 ml/kg and 59 ml/kg respectively), decreased rapidly during the first few months and became relatively stable at levels of 57 ml/kg and 44 ml/kg from the age of 100 days. It was possible to predict both plasma volume and red cell volume using parameters of body size other than bwt.