Electromagnetic Blood Flow Recording and Balance of Nutrients in the Udder of Lactating Cows1

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Abstract
An electromagnetic method was adapted to quantitatively measure blood flow through an external pudic artery of the udder in lactating cows during several months. Blood flow through the ipsilateral external pudic vein was blocked while blood was taken from a subcutaneous abdominal vein. Blood flow to milk yield ratio amounted to a mean value of 507:1 in three cows. Peak milk yield occurred before the time of our experiments. There was a high correlation (r = .73) between mammary arterial blood flow and milk yield. Arterio-venous differences (AV) across the udder demonstrated that essential amino acids (EAA) were taken up by the mammary gland in sufficient amounts to account for the EAA secreted as milk protein. Uptake of valine, isoleucine, lysine and particularly that of arginine was in excess of that for milk protein synthesis. There was a highly significant correlation (P<.01) between AV differences of several amino acids and their corresponding arterial concentrations. Uptake of glucose was 19% higher than could be accounted for by secretion as milk lactose. Uptake of plasma triglycerides (TG) accounted for 45% of milk TG. The majority of the TG taken up by the udder was derived from the low density lipoprotein (LDL) fraction Copyright © 1979. American Society of Animal Science . Copyright 1979 by American Society of Animal Science.