Ultrasonic observations on the turnover of ovarian follicular cysts and associated changes of plasma LH, FSH, progesterone and oestradiol-17β in cows

Changes in the diameters of individual follicular structures on ovaries were measured by transrectal ultrasonography for 29 to 40 days and the plasma concentrations of luteinising hormone ( LH), follicle-stimulating hormone ( FSH), progesterone and oestradiol 17β were determined in four cows with ovarian cysts. When these structures decreased in size, new follicular structures appeared and developed into cysts. Progesterone concentrations in plasma were below 1·0 ng ml −1 during the experimental periods. Plasma concentrations of oestradiol-17β fluctuated. The mean concentration of oestradiol-17β in plasma differed (P