Another situation found was the presence of non-pregnant anestrous sows. Out of 1990
sows evaluated, 17 (0.8%) were not pregnant, out of which five had ovarian cysts (i.e.,
almost one-third, 29.4%) of all cases in both farms were associated with cysts. Miller
(1984) suggested that large cysts have luteinized tissue that can produce progesterone in an
amount great enough to suppress onset of estrus, thus causing an increase in the non-pregnant
anestrous sow rate.