Progesterone and total unconjugated oestrogen concentrations in the peripheral blood of 4 Afrikaner cows during late gestation and parturition were determined by RIA. From l2-18 days prepartum, progerone levels ranged .from 8.4 to 13,0 ng/ml and subsequently declined to 3,7-8,2 ng/ml at l – 2 days prior to parturition. During the following 12-24 hours progesterone concentration dropped sharply to 1,2- 2,0 ng/ ml, these levels being measured 12-18 hours prior to calving. A moderate rise in progesterone levels not previously reported was observed during the subsequent parturition and 24 hours thereafter .Minimum progesterone levels (< l ng/nl ) were reached 24-48 hours post partum. Oestrogen levels ranging between 193 and 267 pg/ml 19-22 days prepartum increased consistently to 453-687 pg/ml at 3-5 days before parturition. Thereafter levels declined slightly with the approach of parturition, and then dropped sharply ‘ from 271-523 pg/ ml just prior to calving to 96-145 pg/ml shortly thereafter .Two day s after parturition oestrogen concentration averaged 110 pg/ml with very little variation between individuals.
"Experientia docet" - Experience is the best teacher