RELATIONSHIPS BETWEEN THE STEROID-HORMONE PROFILES AND PRODROMAL EXTERNAL SIGNS OF CALVING

In 22 healthy German Black Pied cows, the rectal temperature and tempo ral changes of seven prodromal, external signs of parturition were rec orded twice daily during the last eight days of gestation. During the same period plasma concentrations of progesterone and total oestrogens were estimated by radio-immunoassay. During the last 6 days of pregna ncy plasma concentration of total oestrogens increased progressively u ntil calving. From 60 to 12 hours before calving, progesterone concent rations declined rapidly from 5.5 +/- 2.5 ng/ml to a mean minimum leve l of 0.8 +/- 0,2 ng/ml. Statistically significant positive correlation s were found between total oestrogens and oestrogen/progesterone ratio and external signs of imminent calving (vulva swelling, relaxation of the broad pelvic ligaments and flexibility of the tail). Statisticall y significant negative correlations were found between plasma progeste rone concentration and the parameters mentioned above. Close relations hips were observed between the precalving decline in body temperature and the progesterone concentration and the oestrogen/progesterone rati o, the former being positive and the latter negative. The oestrogen/pr ogesterone ratio may be the predominant factor regulating body tempera ture during the precalving phase.