Increased fertility in lactating dairy cows resynchronized with Double-Ovsynch compared with Ovsynch initiated 32 d after timed artificial insemination

• Published in: Journal of dairy science 2012-02, Vol.95 (2), p.639-653
• Main Authors: Giordano, J.O., Wiltbank, M.C., Guenther, J.N., Pawlisch, R., Bas, S., Cunha, A.P., Fricke, P.M.
• Format: Article
• Language: English
• Subjects: Abortion, Veterinary - physiopathology; Animal productions; Animals; artificial insemination; Biological and medical sciences; blood serum; Cattle; corpus luteum; dairy cow; dairy cows; Double-Ovsynch; Estrus - physiology; Estrus Synchronization - methods; Female; fertility; Fertility - physiology; Food industries; Fundamental and applied biological sciences. Psychology; gonadotropin-releasing hormone; Holstein; Insemination, Artificial - methods; Insemination, Artificial - veterinary; lactation; Lactation - physiology; Milk and cheese industries. Ice creams; ovulation; Ovulation - physiology; Pregnancy; progesterone; Progesterone - blood; resynchronization; Terrestrial animal productions; ultrasonography; Vertebrates
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.2011-4418

The objective was to determine if using a Double-Ovsynch protocol [DO; Pre-Resynch: GnRH–7 d–PGF2α–3 d–GnRH, 7 d later Breeding-Resynch: GnRH–7 d–PGF2α–56 h–GnRH–16 h–timed artificial insemination (TAI)] to resynchronize ovulation after a previous TAI would increase synchrony and pregnancies per AI (P/AI) compared with an Ovsynch protocol initiated 32 d after TAI (D32; GnRH–7 d–PGF2α–56 h–GnRH–16 h–TAI). Lactating Holstein cows at various days in milk and prior AI services were blocked by parity and randomly assigned to resynchronization treatments. All DO cows received the first GnRH injection of Pre-Resynch 22 d after TAI, and cows (n=981) diagnosed not pregnant using transrectal ultrasonography 29 d after TAI continued the protocol. Pregnancy status for all D32 cows was evaluated 29 d after TAI so fertility and pregnancy loss could be compared with that of DO cows. All D32 cows received the first GnRH injection of Ovsynch 32 d after TAI, and cows (n=956) diagnosed not pregnant using transrectal palpation 39 d after TAI continued the protocol. In a subgroup of cows from each treatment, ultrasonography (n=751) and serum progesterone (P4) concentrations (n=743) were used to determine the presence of a functional corpus luteum (CL) and ovulation to the first GnRH injection of D32 and Breeding-Resynch of DO (GnRH1), luteal regression after PGF before TAI, and ovulation to the GnRH injection before TAI (GnRH2). Overall, P/AI 29 d after TAI was not affected by parity and was greater for DO compared with D32 cows (39 vs. 30%). Pregnancy loss from 29 to 74 d after TAI was not affected by parity or treatment. The percentage of cows with a functional CL (P4 ≥1.0ng/mL) at GnRH1 was greater for DO than D32 cows (81 vs. 58%), with most DO cows having medium P4 (60%; 1.0 to 3.49ng/ml), whereas most D32 cows had either low (42%;