Cows without PVD (VDS-0 and VDS-1) were excluded from these analyses. We evaluated the effect of treatment with PGF2α in cows with PVD (VDS-2 and VDS-3) on FSCR and detected an interaction of parity and treatment (P = 0.029). Therefore, we analyzed the effects of treatment on FSCR separately for primiparous and multiparous cows. In primiparous cows with PVD (n = 190), there was an interaction of treatment with PGF2α and presence of a CL (P = 0.044; Figure 5). There was no treatment effect in primiparous cows with PVD and a CL (P = 0.888). However, there was a treatment effect in primiparous cows with PVD and without a CL (P = 0.010). No other explanatory variable remained in the final model for primiparous cows. In multiparous cows with PVD (n = 288), there was a treatment effect on FSCR (P = 0.050; Figure 5). Multiparous cows with PVD treated with PGF2α had increased odds (odds ratio = 1.66; 95% CI 1.00 to 2.76; P = 0.050) of pregnancy at first AI compared withcontrol cows with PVD. No interaction was observed between treatment and presence of a CL (P = 0.512). Time to first AI (P = 0.023) was the other explanatory variable that remained in the final model for multiparous cows. Treatment with PGF2α had no effect on time to first AI (P = 0.907) using the Cox proportional hazard model (n = 531). No interaction was observed between parity and VDS (P = 0.697). Body condition score (P = 0.058) and first test-day milk yield (P = 0.051) were the other explanatory variables that remained in the final model.