remained visible at the ultrasound examination for at least 5 days after estrus onset was
present. The sows that did not show any cysts were followed by ultrasound examination
until the time of ovulation. Ovulation was considered to have occurred at the time which
preovulatory follicles (usually between 0.8 and 1.2 cm) were no longer present. In farm A,
ovarian cysts were followed until the seventh day after estrus onset and in farm B until the
15th day after estrus onset