title: Comparison of fertility, regular returns-to-estrus, and calving interval between Ovsynch and CO-synch + CIDR protocols in dairy cows.
abstract: The main aims of the present study were to compare the pregnancy rate (PR), regular returns-to-estrus, and calving interval of a CO-Synch + controlled internal drug release (CIDR) device, commonly used to synchronize ovulations in beef cows, with the classical Ovsynch protocol in high-producing dairy cows. Holstein-Friesian cows (n = 128) from six commercial dairy herds, ≥40 days postpartum and not previously inseminated, were randomly assigned to one of two treatments. Cows submitted to Ovsynch protocol (group OS as control group; n = 66) received 10 μg of a GnRH analogue 7 days before and 48 hours after 25 mg PGF2α, followed by artificial insemination (AI) 16 hours after the second GnRH administration. Cows submitted to CO-Synch + CIDR (1.38 g of progesterone) inserted for 7 days beginning at the first GnRH administration (group CoS + CD; n = 62) had the second administration of GnRH concurrent with AI, 64 hours after CIDR removal/PGF2α administration. Nonpregnant cows with return-to-estrus between 18 and 24 days after first AI were reinseminated (second AI). Logistic regressions were used to analyze PR and returns-to-estrus. No effect of group or herd was observed in PR at first timed AI. However, the sum of cows pregnant at first AI and nonpregnant cows with regular returns-to-estrus and the total PR (first + second AI) were influenced by group treatment. Overall, cows of group CoS + CD (total PR = 56.5%) were 2.1 times more likely to became pregnant after AI and until first regular returns-to-estrus than cows of group OS. The calving interval was lower in group CoS + CD (425.9 ± 78.8 days; ±SD) than in group OS (475.3 ± 83.7 days). The CO-Synch + CIDR protocol was reliable to use in dairy herds and provided reproductive advantages when compared with Ovsynch protocol.
authors.affiliation: Medicina de Produção Leiteira Veterinária Lda. (MPLVET), Tocha, Portugal.
authors.forename: C
authors.initials: C
authors.lastname: Azevedo
authors.affiliation: Medicina de Produção Leiteira Veterinária Lda. (MPLVET), Tocha, Portugal.
authors.forename: I
authors.initials: I
authors.lastname: Maia
authors.affiliation: Department of Veterinary Clinics, Abel Salazar Institute of Biomedical Sciences, Rua Jorge Viterbo Ferreira, Porto, Portugal. Electronic address: nfcanada@icbas.up.pt.
authors.forename: N
authors.initials: N
authors.lastname: Canada
authors.affiliation: Department of Veterinary Sciences, University of Trás-os-Montes e Alto Douro, Vila Real, Portugal.
authors.forename: J
authors.initials: J
authors.lastname: Simões
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D003612:Dairying; D015237:Dinoprost / Q000494:pharmacology*; D004971:Estrus / Q000187:drug effects* / Q000502:physiology; D004973:Estrus Synchronization / Q000187:drug effects*; D005260:Female; D005298:Fertility; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D007315:Insemination, Artificial / Q000662:veterinary; D010120:Oxytocics / Q000494:pharmacology; D011247:Pregnancy; D018873:Pregnancy Rate
chemical_list: D010120:Oxytocics; D007987:Gonadotropin-Releasing Hormone; D015237:Dinoprost
keywords: Artificial insemination; CO-Synch + CIDR; Dairy cattle; Fertility; Ovsynch