Cryopreservation allows for long-term storage of semen. However, cryopreservation and thawing imposes stress on spermatozoa, and prematurely initiates the process of capacitation; possibly decreasing sperm lifespan. Liquid semen is not exposed to these stressors, leading to a potential longer lifespan in the female reproductive tract and thus increasing the window for successful insemination. The objective of this study was to compare fertility of liquid and frozen semen when varying the interval from CIDR removal to insemination using the 7-d CO-Synch + CIDR protocol. Within age group cows (n = 389) were randomly assigned to insemination at 36 or 60 h after CIDR removal with either liquid (36L and 60L) or frozen semen (36F and 60F). Cows were monitored for estrus activity from CIDR removal to 60 h after CIDR removal. Cows that failed to exhibit estrus received an injection of GnRH (100 µg) and a blood sample was collected for analysis of estradiol concentration. Data were analyzed using the GLIMMIX procedure of SAS with sire and herd as random variables. There was no difference in pregnancy rates between liquid or frozen semen (53% and 52%), but cows inseminated at 60 h had greater (P < 0.01) pregnancy rates than cows inseminated at 36 h (72% and 31%). There was no interval by semen type interaction (P = 0.57). Estrus was detected in 63%, 61%, 56%, and 62% of 36F, 36L, 60F, and 60L, respectively (only 5% and 1% of 36F and 36L were detected in estrus before insemination). Overall cows that exhibited estrus had greater pregnancy rates compared with cows that did not (P < 0.01; 79% and 24%). Among cows that did not exhibit estrus, those inseminated with liquid semen tended to have greater pregnancy rates than those inseminated with frozen semen (P = 0.06), and ones that became pregnant had elevated (P < 0.01) concentrations of estradiol at 60 h (10.7 ± 1.9 vs 7.9 ± 2.9 pg/mL). In summary, there was no difference in pregnancy success between liquid and frozen semen. However, cows that exhibited estrus and inseminated at 60 h after CIDR removal had greater pregnancy success compared with cows that did not exhibit estrus.