Plasma Progesterone Concentration after Removal of the Corpus Luteum in the Cow

Abstract

PLASMA progesterone concentration was determined in serial 1-l. blood samples taken from normal dairy cows at mid-cycle after removal of the corpus luteum. The method of Short1, with some modification, notably the incorporation of an internal marker of progesterone-4-14C for individual recoveries, was used for progesterone determination. In addition it was found necessary to acetylate the first chromatogram eluate and subject it to rechromatography2,3. Recoveries were comparable with those obtained for bovine plasma by Short1 and averaged 50 per cent with a range of 40–60 per cent. Corpora lutea were removed under posterior epidural anaesthesia via the vagina by making a 3-cm incision, in the dorsal vaginal fornix, and manipulating the ovaries into the vagina where the corpus luteum was easily enucleated. In this position the ovaries could be inspected by means of a vaginal speculum for either residual tissue left after enucleation or other corpora lutea.