Factors associated with ovarian structures and intrauterine fluid in the postpartum period in dairy cows. 
The objective was to examine risk factors for the interval to resumption of ovarian cyclicity (ROC), multiple ovulations (MCL), ovarian follicular cysts (OC), and presence of intrauterine fluid (IUF) at 22 to 28 [visit (V) 1] and 36 to 42 (V2) days in milk (DIM) in dairy cows.  The study was conducted retrospectively by evaluating records from 1,155 Holstein cows from 3 herds.  Ovaries and uteri were examined at V1 and V2 by transrectal ultrasonography to determine ovarian structures and IUF.  Based on the odds ratio, multiparous cows were more likely to have ROC at V1 by a factor of 1.79 compared with primiparous cows.  The likelihood of ROC at V1 was lower in cows with higher milk production, in cows with retained fetal membranes (RFM) or cows with IUF at V1 by factors of 0.98 (for each kg of milk increased), 0.52, and 0.61, respectively.  Based on the odds ratio, cows diagnosed with IUF at V2 were 2.85 times more likely to have attained ROC at V2.  Multiparous cows and cows that delivered twins were 2.73 and 2.16 times, respectively, more likely to have MCL at V1, whereas cows with RFM were 0.38 times less likely to have MCL at V1.  The likelihood of MCL at V2 was higher in cows with MCL and OC at V1 by factors of 2.67 and 1.91, respectively.  Multiparous cows were 8.51 times more likely to have OC at V1 than primiparous cows.  Higher producing cows were more likely to have OC at V2 by a factor of 1.04 compared with lower producing cows.  Parity, stillbirth, RFM, and ROC at V1 were all identified as risk factors for IUF at V1.  Cows with RFM and delivering twins were more likely to be diagnosed with IUF at V2 by a factor of 3.43 and 4.07, respectively.  In summary, parity, twinning, RFM, metritis, IUF, and milk production were all associated with altered ovarian structures, and the presence of IUF was related to parity, twinning, RFM, and ROC in postpartum dairy cows.