INCIDENCES AND ASSOCIATIONS OF CYSTIC OVARIES WITH PRODUCTION AND REPRODUCTION TRAITS IN DAIRY-CATTLE

Data were from the records of 243 Guernsey and 453 Holstein cows owned by the University of Missouri-Columbia. Records were collected from 1977 through 1987. Lactational incidence of cystic ovaries (cysts) averaged 37.9 and 38.2% in Guernsey and Holstein breeds, respectively. Incidence of cystic ovaries was not significantly different between seasons however, it appeared higher during autumn month for both breeds. Multiple logistic regressions with a stepwise option indicated that the effects of year of calving and preceding days dry increased the incidence of cysts in Guernseys. In Holsteins, incidence was increased with increasing pr ceding calving interval and age; year of calving showed a curvilinear relationship with cyst incidence. In both breeds, cows with cysts produced more milk and fat but also had more days open than their noncystic contemporaries. Cyst development did not affect days in milk or number of services per conception. Repeatability of cyst development was .20 in Guernseys and .06 in Holsteins. Corresponding estimates on a normal distribution scale were .33 and .10, respectively.