The objective was to compare pregnancy per artificial insemination (P/AI) with conventional (CS) or sex-sorted semen (SS) in dairy cows subjected to one of the three timed AI protocols. Cows (n = 356) were randomly assigned to synchronization with Ovsynch (OVS), Presynch-Ovsynch (PO) or Double-Ovsynch (DO) and inseminated on Day 77 ± 3 postpartum with either frozen-thawed SS (n = 182) or CS (n = 184) of the same bull. More cows were cyclic at the beginning of breeding Ovsynch increased (p < 0.01) with presynchronization and it was greater for DO than PO (OVS = 78.5%, PO = 85.1%, DO = 95.6%). Overall, P/AI for SS and CS increased with presynchronization (p < 0.05) on Days 31 (OVS = 35.5%, PO = 47.1%, DO = 48.3%) and 62 (OVS = 30.1%, PO = 43.8%, DO = 43.9%). Regardless of synchronization treatments, insemination with SS reduced P/AI (p < 0.02) on Days 31 (38.1% vs. 50.6%) and 62 (34.5% vs. 45.6%) compared with CS. No interaction was observed between synchronization treatment and type of semen for P/AI, although in cows receiving CS, P/AI was numerically greatest for PO (OVS = 42.0%, PO = 59.3%, DO = 49.0%), and in cows receiving SS, it was numerically greatest for those inseminated following DO (OVS = 27.9%, PO = 35.5%, DO = 47.6%). Thus, presynchronization improved P/AI in cows inseminated with sex-sorted or conventional semen.
Keywords: dairy cow; ovsynch; presynchronization; sex-sorted semen.
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