Measurements of progesterone and estradiol 17-beta concentrations within the first 36 days of pregnancy were taken in order to study the relationship between their concentrations and the ultrasound embryonic vesicle examination in 30 Thoroughbred mares. Two groups of 15 animals each were used, one consisting of maiden or barren mares from the previous breeding season, and the other one of foaling mares. The phenomena of mobility, fixation and orientation of the embryonic vesicle were studied, and no relationship between hormone concentration and the development of the concept was found. The concentration of oestrogens was higher (P<0.01) in the foaling mares.
Mare; progesterone; estradiol 17-beta; ultrasound; pregnancy
