Prostaglandin f2α

Cows were housed at the University of Wisconsin-Madison Dairy Cattle Research Center (Arlington, WI) in loose housing with headlocks. Cows were fed ad libitum a TMR formulated to meet or exceed NRC (2001) requirements for high-producing dairy cows. Primiparous cows were housed separately from multiparous cows. The rolling herd average was 13,880 kg and average daily milk production was 41.6 kg/cow per day with 3.8% fat and 3.2% protein for the herd during the study period.
Lactating Holstein cows (n = 141; 41 primiparous and 100 multiparous) from 53 ± 3 DIM were synchronized for first TAI using a Double-Ovsynch protocol (Souza et al., 2008) . Prostaglandin F 2α (25 mg/dose of dinoprost tromethamine; Lutalyse) and GnRH (100 µg/dose of gonadorelin hydrochloride; Factrel) were from Zoetis (Madison, NJ). Briefly, cows received the first GnRH treatment of the Presynch portion of the Double-Ovsynch protocol at 53 ± 3 DIM, followed by treatment with PGF 2α 7 d later and a GnRH treatment 72 h after PGF 2α . Seven days later, cows received an Ovsynch-56 protocol (GnRH at 70 ± 3 DIM, PGF 2α 7 d later, GnRH 56 h after PGF 2α , and AI 16-20 h later), and all cows received a TAI at 80 ± 3 DIM. Three experienced AI technicians performed all inseminations using sires with high genetic merit and proven fertility.