Clinical signs and hormonal changes in dairy heifers after induction of parturition with prostaglandin F-2 alpha

Parturition was induced in 12 dairy heifers with prostaglandin (PG) F-2 alp ha about 2 weeks before the expected time of calving. Eight animals gave bi rth after two injections (group 1), three animals needed more than two inje ctions (group 2) and one animal (cow no. 740) required one injection. All a nimals in groups 1 and 2 had retained foetal membranes and the time needed to induce parturition was 59 +/- 7 and 149 +/- 10 h, respectively. As cow n o. 740 did not have retained foetal membranes and calved 24 h after one PGF (2 alpha) injection, it was excluded from the results. Udder distension and relaxation of the pelvic ligaments could predict the calving to within 12 h. Furthermore, the pre-calving drop of body temperature could predict the time of parturition to within 16 h. The total white Blood cells and polymor phonuclear cells were at their highest values on the day preceding parturit ion whereas mononuclear cells had a tendency to increase 3 days after calvi ng. Increased levels of haemoglobin were found at the time of parturition, whereas, plasma-calcium levels significantly decreased after parturition (P < 0.001). Progesterone levels markedly decreased after the first PGF(2 alp ha) injection and reached 2 nmol/l at the time of parturition. Plasma level s of oestradiol-17 beta reached the peak at the time of parturition, wherea s, the highest levels of the PGF(2 alpha) metabolite and cortisol were reco rded 16 h after calving.