Colloidal Osmotic Pressures of Fetal and Maternal Plasmas of Sheep and Goats

Abstract

The colloidal osmotic pressure (COP) and the protein concentration in the plasma of fetal and maternal bloods of sheep and goats were measured. The COP of the maternal plasma is 317 [plus or minus] 15 mmH2O in goats and 372 [plus or minus] 12 mmH2O in sheep. The COP of the fetal plasma at 64 days of age is about 100 mmH2O; as development advances the COP gradually increases and reaches the value of about 250 mmH2O near term. It follows that the COP of the maternal plasma is higher than that of the fetal and that the magnitude of the difference is greater in early stages of development. It was calculated that the mean molecular weight of the fetal plasma proteins is 65,200 [plus or minus] 600 and that of the globulin fraction plus fibrinogen about 59,000. The mean molecular weight of the globulin fraction of the adult s plasma proteins is about 130,000. Hence the mean molecular weight of the fetal globulins appears to be only half of the mean molecular weight of the adult s globulins. After birth, the ingestion of colostrum is followed within 24 hours by a rapid increase of the mean molecular weight of the plasma proteins. If the lamb is fed with cow''s milk no such change takes place.