Measurement of Bovine Plasma and Blood Volume During Pregnancy and Lactation

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Abstract
The T-1824 hematocrit method of measuring plasma and blood volume was adapted for use in pregnant and in lactating cows. The dye concn. in sera from cows in either condition was consistent with Beer''s law within an optical density range of 0.4-1.2 and had a max. light absorption at 620 mu. Disappearance rates and mixing times of the dye in the circulations of both types of cows were within the respective control ranges found in a previous study on reproductively inactive cattle. Using Allen''s T-1824 extraction procedure no dye was found in the fetal blood or fetal fluids after injn. into 5 pregnant cows, but traces were extracted from the milk of 3 of 6 lactating cows. This loss did not invalidate the T-1824 method in these animals. Plasma and blood volume detns. on 20 primiparous cows during gestation showed an increase in blood and plasma volume in excess of that accompanying maturing growth. Detns. on 7 cows, which had calved for the 1st time, showed that during lactation the increased volumes were maintained. Milk secretion in these cows represented an avg. daily turnover of 85% of the plasma volume.

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