Ovarian cysts are an important cause of reduced reproductive performance in gilts and sows. The formation of follicular cysts, although not completely elucidated yet, is associated with a deficiency in LH release and the continuous growth of follicles. Luteal cysts might arise from ovulated follicles due to premature closure of the ovulation site. The formation of ovarian cysts is probably multifactorial. Genetic factors may affect the susceptibility to this fertility disorder. Risk factors for the development of ovarian cysts are stress, mycotoxins and hormonal treatment over a long period of time, or at an improper phase of the reproductive cycle. Other, still unknown risk factors may be involved. Ovarian cysts can cause anestrus, irregular estrus cycles, behavioral changes, lower conception rates and a reduced litter size. However, not all ovarian cysts are clinically apparent. The diagnosis of ovarian cysts is based on ultrasonography. Various treatments are possible (GnRH, hCG or PGF(2a)) but the effectiveness is unsatisfactory. Therefore, in most cases the sow is culled
