Cystic ovarian disease in cows is usually seen in the first two months post calving.
Traditionally cysts have been defined as anovulatory follicular structures (diameter, >25 mm) that persist for 10 or more days in the absence of a functional corpus luteum and are accompanied by abnormal oestrous behaviour (irregular oestrus intervals, nymphomania or anoestrus). However, recent data using ultrasonography indicate that follicles typically ovulate at 17 mm in diameter, so follicles that persist at 17mm or greater may be considered to be "cystic."
Cystic ovarian disease in dairy cattle occurs most frequently during the post partum period, 30 to 60 days after calving, when normal ovarian activity usually resumes.
The incidence of COD varies between 5 and 30 % (Kesler and Garverick 1982; Lopez-Diaz and Bosu 1992; Laporte et al., 1994; Hooijer et al., 2001)
Each incidence of ovarian follicular cysts increase the calving interval by 22-64 days (after Hatler et al., 2003.)
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