[Corpora lutea with and without cavities in cattle. Their occurrence and their development in estrus and during early...

Occurrence and development of cystic and non-cystic corpora lutea were compared during oestrus cycle and in early pregnancy. Using ultrasound scanning in 24 (47%) of 51 oestrus cycles of 12 heifers a cavity greater than or equal to 7 mm in their corpora lutea could be detected at least at one day of the cycle. This could also be observed in 9 (53%) of 17 heifers in the first three weeks of gestation. The culmination of the cavity development was around day 9 after oestrus in normal cycles and in early pregnancy. At this time 41% of cycling heifers and 36% of pregnant heifers had a corpus luteum with a cavity greater than or equal to 7 mm, the largest diameters of the cavities being 11 mm. After day 9 the cavities decreased by half a millimeter a day. Cystic corpora lutea were longer and wider, and had more luteal tissue than non-cystic structures in both reproductive stages. Percentage and size parameters of cystic corpora lutea showed no apparent discrepancy between oestrus cycles and early pregnancy. Fertility of heifers with cystic structures did not indicate a pathological implication of the cavity.