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 rechromatography^2,3. 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 anæsthesia 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.