Double-Ovsynch in high-producing dairy cows: Effects on progesterone concentrations and ovulation to GnRH treatments

Abstract Previous studies reported increased fertility using Ovsynch for presynchronization before Ovsynch (Double-Ovsynch), as compared with presynchronization with two prostaglandin F 2α (PGF 2α ) treatments before Ovsynch (Presynch-Ovsynch). This study compared ovarian follicular dynamics and hormone concentrations during Double-Ovsynch versus Presynch-Ovsynch. Lactating Holstein cows (N = 193) were assigned to one of two treatment groups: (1) Presynch (N = 93), two injections of PGF 2α 14 days apart, followed by the Ovsynch-timed AI protocol 12 days later; and (2) Double-Ovsynch (N = 100), one injection of GnRH, PGF 2α 7 days later, and GnRH 3 days later, followed by the Ovsynch-timed AI protocol 7 days later. All cows received the same Ovsynch-timed AI protocol: GnRH (G1) at 68 ± 3 days in milk (mean ± SEM), PGF 2α 7 days later, and GnRH (G2) 56 hours after PGF 2α . Ultrasonographic evaluations of the ovaries and blood sampling were performed at G1, PGF 2α , G2, and 6 days after the G2 injection of the Ovsynch-timed AI protocol. Double-Ovsynch decreased the percentage of cows with low circulating progesterone (P4) concentrations ( P4 ≤ 3.0 ng/mL) at G1 (80.0% vs. 57.0%; P 3.0 ng/mL) at PGF 2α (88.0% vs. 76.3%; P = 0.04) and tended to increase average circulating P4 at PGF 2α (3.52 ± 0.17 ng/mL vs. 3.09 ± 0.21 ng/mL; P = 0.11). Double-Ovsynch also tended to increase percentage of cows ovulating to G1 (80.0% vs. 69.9%; P = 0.11) and G2 (98.0% vs. 93.5%; P = 0.08). Thus, presynchronization of cows with Double-Ovsynch induced ovulation in noncycling cows and appeared to increase most aspects of synchronization during the Ovsynch protocol.