Biliary elimination of endogenous nortestosterone by pregnant cows
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Updated: Oct 28, 2026

Bovine Ovarian Cortex Tissue Culture
Published on: January 14, 2021
J D McEvoy1, C E McVeigh, W J McCaughey
1Residues Department, Department of Agriculture for Northern Ireland, Belfast.
Abstract:
A temporal study of the biliary elimination of endogenous 19-nortestosterone during two successive pregnancies was made in three cows with cannulated gall bladders. Bile samples were analysed for 17 beta-19-nortestosterone (beta-NT) and the 17 alpha-epimer (alpha-NT) by using high resolution gas chromatography and mass spectroscopy. No beta-NT was detected in any of the samples analysed. However, alpha-NT was detected from around 120 days of gestation in each of the cows. Peak concentrations were observed in the last week before calving and ranged from 9.5 to 36.7 ng/ml. After parturtion, the concentrations of alpha-NT declined rapidly and were undetectable by seven days after calving, and it was not detected again until after 120 days of gestation. The biliary concentrations of alpha-NT detected subsequently were similar to those observed in cattle several weeks after an exogenous injection of the synthetic ester beta-NT phenylpropionate.
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