A new presynchronization system (Double-Ovsynch) increases fertility at first postpartum timed AI in lactating dairy cows.
This study evaluated a novel presynchronization method, using Ovsynch prior to the Ovsynch-timed AI protocol (Double-Ovsynch) compared to Presynch-Ovsynch. Lactating Holstein (n=337) cows, were assigned to two treatment groups: (1) Presynch (n=180), two injections of PGF 14 d apart, followed by the Ovsynch-timed AI protocol 12 d later; (2) Double-Ovsynch (n=157), received GnRH, PGF 7 d later, and GnRH 3 d later, followed by the Ovsynch-timed AI protocol 7 d later. All cows received the same Ovsynch-timed AI protocol: GnRH (G1) at 68+/-3 DIM (mean+/-SEM), PGF 7 d later, GnRH (G2) 56h after PGF, and AI 16 to 20h later. Pregnancy was diagnosed 39-45 d after timed AI. Double-Ovsynch increased the pregnancies per AI (P/AI) compared to Presynch-Ovsynch (49.7% vs 41.7%, P=0.03). Surprisingly, Double-Ovsynch increased P/AI only in primiparous (65.2% vs 45.2%; P=0.02) and not multiparous (37.5% vs 39.3%) cows. In a subset of 87 cows, ovarian ultrasonography and progesterone (P4) measurements were performed at G1 and 7 d later. Double-Ovsynch decreased the percentage of cows with low P4 (<1ng/mL) at G1 (9.4% vs 33.3%) and increased the percentage of cows with high P4 (> or =3ng/mL) at PGF (78.1% vs 52.3%). Thus, presynchronization of cows with Double-Ovsynch increased fertility in primiparous cows compared to a standard Presynch protocol, perhaps due to induction of ovulation in non-cycling cows and improved synchronization of cycling cows. Future studies are needed, with a larger number of cows, to further test the hypothesis of higher fertility with Double-Ovsynch, and to elucidate the physiological mechanisms that underlie apparent changes in fertility with this protocol.
Souza
A H
AH
Department of Animal Reproduction, University of São Paulo, São Paulo 05508, Brazil.
Ayres
H
H
Ferreira
R M
RM
Wiltbank
M C
MC
D000818:Animals; D002417:Cattle / Q000502:physiology*; D003612:Dairying; D015237:Dinoprost / Q000008:administration & dosage / Q000494:pharmacology*; D004973:Estrus Synchronization / Q000379:methods*; D005260:Female; D005298:Fertility; D005300:Fertility Agents, Female / Q000008:administration & dosage / Q000494:pharmacology; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D007315:Insemination, Artificial / Q000662:veterinary*; D007774:Lactation / Q000502:physiology*; D010053:Ovary / Q000187:drug effects / Q000502:physiology; D010298:Parity; D049590:Postpartum Period; D011247:Pregnancy; D018873:Pregnancy Rate
D005300:Fertility Agents, Female; D007987:Gonadotropin-Releasing Hormone; D015237:Dinoprost