The inoculation of viable cultures of Vibrio fetus into the uterus of cows in the second and third 3-monthly periods of pregnancy resulted in abortion. All foetuses exposed during the second 3 months were aborted 5 to 7 days post-inoculation; foetal death occurred several days before expulsion. Peripheral plasma progesterone levels declined at the time of foetal death.
Cows injected with V. fetus during the third 3 months of pregnancy aborted 9 to 20 days post-inoculation and in a majority of cases delivered live calves. The decline of progesterone levels on the day of abortion is very similar to that observed before normal parturition. Progesterone levels in the dam reflect the viability status of the foetus. The decline of progesterone associated with abortion may be due both to placental dysfunction as well as luteolysis of the cl because of the release of products from the infected foetus.
If the inline PDF is not rendering correctly, you can download the PDF file here.