Is there a predictable correlation between time of birth, birth and after birth period and clinical and hormonal findings in mares?

The investigations were done on 108 mares (78 warm-blooded horses, 25 cold- blooded horses and 5 trotters). To pursue the question in the title, proges terone and estradiol values in jugular veinblood were examined starting fro m 30 days before the calculated date of parturition until 30 days after tha t event. In parallel to that Ca/Mg ratio was measured by means of a semiqua ntitative test-strip in the milk. Clinical signs of the birth, parturition itself and the post partum period were recorded. In respect to the P4 and E 2 values it was that the P4:E2 ratio changed towards parturition in favour to E2 which was interpreted as a sign for the beginning of labour contracti ons as well as a signal to the ovarian hormonal activity and feed-back regu lation. The "predict of the foal-test" by measuring Ca/Mg ratio is helpful only in combination with clinical findings. This test can be used for the decision to induce parturition. Concerning the colour and viscosity of the milk, it was observed to change from grey-aqueous 48 h a.p. through grey-brownish 24 h a.p. to white-yellow and viscous 12h a.p. The results show that heavy mares more often retain the fetal membranes. Th ey often bear lighter offspring with equally lighter fetal membranes, and t he surfaces of the microvilli of the microcotyledonas seem to be smaller. B eside this it is concluded that during pregnancy disturbances in the fetoma ternal relations probably exist as a result of a deficiency in placental de velopment that finally results in retentio secun-dinarum.