title: Factors affecting synchronization and conception rate after the Ovsynch protocol in lactating Holstein cows.
abstract: Objectives were to evaluate risk factors affecting ovulatory responses and conception rate to the Ovsynch protocol. Holstein cows, 466, were submitted to the Ovsynch protocol [day 0, GnRH-1; day 7, prostaglandin (PG) F(2alpha); day 9, GnRH-2] and 103 cows were inseminated 12 h after GnRH-2. Information on parity, days in milk at GnRH-1, body condition, milk yield, exposure to heat stress, pre-synchronization with PGF(2alpha) and the use of progesterone insert from GnRH-1 to PGF(2alpha) was collected. Ovaries were scanned to determine responses to treatments. Overall, 54.7%, 10.6%, 2.2%, 81.1%, 9.0%, 91.5% and 36.9% of the cows ovulated to GnRH-1, multiple ovulated to GnRH-1, ovulated before GnRH-2, ovulated to GnRH-2, multiple ovulated to GnRH-2, experienced corpus luteum (CL) regression and conceived, respectively. Ovulation to GnRH-1 was greater in cows without a CL at GnRH-1, cows with follicles >19 mm and cows not pre-synchronized with PGF(2alpha) 14 days before GnRH-1. Multiple ovulations to GnRH-1 increased in cows without CL at GnRH-1 and cows with follicles < or =19 mm at GnRH-1. Ovulation before GnRH-2 was greater in cows without CL at PGF(2alpha). Ovulation to GnRH-2 increased in cows that received a progesterone insert, cows with a CL at GnRH-1, cows with follicles not regressing from the PGF(2alpha) to GnRH-2, cows with larger follicles at GnRH-2, cows that ovulated to GnRH-1 and cows not pre-synchronized. Multiple ovulations after GnRH-2 increased in cows with no CL at GnRH-1, multiparous cows and cows that multiple ovulated to GnRH-1. Conception rate at 42 days after AI increased in cows with body condition score > 2.75 and cows that ovulated to GnRH-2. Strategies that optimize ovulation to GnRH-2, such as increased ovulation to GnRH-1, should improve response to the Ovsynch protocol.
authors.affiliation: Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA. kag73@cornell.edu
authors.forename: K N
authors.initials: KN
authors.lastname: Galvão
authors.forename: J E P
authors.initials: JE
authors.lastname: Santos
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D003338:Corpus Luteum / Q000502:physiology; D015237:Dinoprost / Q000008:administration & dosage; D004973:Estrus Synchronization / Q000379:methods* / Q000502:physiology*; D005260:Female; D005306:Fertilization / Q000502:physiology*; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage; D007315:Insemination, Artificial / Q000379:methods / Q000662:veterinary; D007774:Lactation / Q000502:physiology*; D016015:Logistic Models; D010053:Ovary / Q000648:ultrastructure; D010062:Ovulation Induction / Q000379:methods / Q000662:veterinary*
chemical_list: D007987:Gonadotropin-Releasing Hormone; D015237:Dinoprost