The objective of this study was to evaluate factors associated with resumption of ovarian cyclicity within 21 days in milk (DIM) in dairy cows. Cows (n=768) from 2 herds in north Florida had their ovaries scanned at 17±3, 21±3, and 24±3 DIM. Cows that had a corpus luteum ≥20mm at 17±3 or at 21±3 DIM or that had a corpus luteum <20mm in 2 consecutive examinations were determined to be cyclic by 21±3 DIM. The following information was collected for up to 14 DIM: calving season, parity, calving problems, metabolic problems, metritis, mastitis, digestive problems, lameness, body weight loss, dry period length, and average daily milk yield. Body condition was scored at 17±3 DIM. Multivariable mixed logistic regression analysis was performed using the GLIMMIX procedure of SAS. Variables with P≤0.2 were considered in each model. Herd was included as a random variable. Three models were constructed: model 1 included all cows, model 2 included only cows from dairy 1 that had daily body weights available, and model 3 included only multiparous cows with a previous dry period length recorded. In model 1, variables associated with greater cyclicity by 21±3 DIM were calving in the summer and fall rather than in the winter or spring, being multiparous rather than primiparous, and not having metabolic or digestive problems. In model 2, variables associated with greater cyclicity by 21±3 DIM were calving in the summer and fall, not having metritis or digestive problems and not losing >28 kg of BW within 14 DIM. In model 3, variables associated with greater cyclicity by 21±3 DIM were absence of metabolic problems and dry period ≤76 d. In summary, cyclicity by 21±3 DIM was negatively associated with calving in winter or spring, primiparity, metritis, metabolic or digestive problems, loss of >28 kg of body weight, and a dry period >76d. Strategies preventing extended dry period length and loss of BW, together with reductions in the incidence of metritis as well as metabolic and digestive problems should improve early cyclicity postpartum.

The objective was to evaluate the individual and combined effect of anovulation and cytological endometritis (CTE) on the reproductive performance of dairy cows. A total of 1,569 cows from 3 data sets were used. In data set 1, 403 Holstein cows from 5 dairies in New York were used. In data set 2, 750 Holstein cows from 2 dairies, one in Florida and one in California were used. In data set 3, 416 dairy cows, 165 Holsteins, 36 Jerseys, and 215 Holstein-Jersey crossbreeds from a grazing dairy in Florida were used. Cyclicity and CTE was determined at 35±3 (data set 2) or 49±3 d in milk (data sets 1 and 3). A variable (VarCycCTE) containing all 4 possible permutations between cyclicity (cyclic = Cyc; anovular = Anov) and CTE (present = CTE; absent = Healthy) was created. In the combined data set (sets 1, 2, and 3), pregnancy per artificial insemination (P/AI) diagnosed at 30 to 38 d after first AI was affected by VarCycCTE, with AnovCTE cows having decreased P/AI compared with CycHealthy cows (21.3 vs. 46.7%), whereas AnovHealthy (37.9%) and CycCTE cows (36.0%) had intermediate P/AI. Pregnancy per artificial insemination for the individual data sets and for pregnancy diagnosed at 63 to 74 d after artificial insemination followed a similar pattern. Pregnancy loss was not affected by VarCycCTE. Hazard of pregnancy up to 300 d in milk was affected by VarCycCTE in the combined data sets 1 and 2, with AnovCTE [hazard ratio (HR)=0.55], AnovHealthy cows (HR=0.71), and CycCTE (HR=0.8) having decreased hazard of pregnancy compared with CycHealthy cows. Median days open were 200, 159, 145, and 121 for AnovCTE, AnovHealthy, CycCTE, and CycHealthy, respectively. Hazard of pregnancy for the individual data sets followed a similar pattern. In summary, both anovulation and CTE were negatively associated with reproductive performance and, when combined, they had an additive negative effect.