Corticosteroid concentrations in jugular and mammary vein blood plasma of cows after overmilking
Paape, M.J.; Desjardins, C.; Schultze, W.D.; Smith, J.W.
American Journal of Veterinary Research 33(9): 1753-1758
1972
ISSN/ISBN: 0002-9645 PMID: 5066124 Document Number: 48608
During normal milking, samples collected from five cows before, immediately after, and at 15, 30, 45 and 90 minutes after milking. The concentrations of plasma corticosteroid corresponding to these sampling times averaged 9.7, 19.7, 20.2, 19.9, 15.5, and 10.0 ng/ml of plasma. During overmilking, samples were collected immediately before and after normal milking, immediately after the 15-minute overmilking period, and at 15, 30, 45 and 90 minutes after milking machine was removed. Plasma corticosteroid concentrations averaged 9.3, 22.0, 20.1, 19.7, 14.8, and 10.0 ng/ml of plasma. The plasma corticosteroid concentration immediately after overmilking was greater than that after normal machine milking. During the non-milking period, samples were collected at the same intervals as during overmilking. In contrast to the dynamic changes in plasma corticosteroid provoked by either normal or overmilking, plasma corticosteroid provoked by either normal or overmilking, plasma corticosteroid concentrations remained relatively constant during non-milking and averaged 9.7 ng/ml of plasma for the 7 sampling periods. Plasma corticosteroid responses to overmilking were also measured in blood samples simultaneously collected from the mammary and the jugular veins of four of the cows. Differences between jugular and mammary corticosteroid concentrations were slight, and the correlation between jugular and mammary samples was 0.96.