Peripheral plasma levels of oestrogens and progesterone during late bovine pregnancy.

Abstract

ABSTRACT The peripheral plasma levels of oestrone* were measured in 127 dairy cows of the Swedish Red and White Breed. The levels recorded during the time period from the 20th to the 35th week of pregnancy were below or about 0.1 ng per ml. After the 35th week of pregnancy the levels increased gradually and maximum levels ranging from 0.5 to 2 ng per ml were found during the last week of gestation. After parturition the levels decreased significantly to about 0.1 ng per ml or less. Six cows were sampled daily from 8 days before until two days after parturition. The peripheral plasma levels of oestrone, oestradiol-17β and progesterone were measured. The oestrone level ranged from about 0.7 to 0.9 ng per ml during the last eight days preceding the delivery. The peripheral plasma levels of oestradiol-17β followed the same pattern as for oestrone. The concentration of oestradiol was only 10 to 20 per cent of the oestrone level. The mean peripheral plasma levels of progesterone were about 4 to 5 ng per ml during the last seven days before partus. A significant drop of the peripheral plasma level of progesterone to an average of 1.8 ng per ml occurred about 24 hours before parturition.