title: Period of dominance of the ovulatory follicle influences embryo quality in lactating dairy cows.
abstract: Length of dominance of the ovulatory follicle and exposure to oestradiol (OE(2)) during proestrus can affect fertility. Lactating cows had their oestrous cycle pre-synchronized and were subjected to one of the four synchronization treatments. Cows in the oestrus detection (OD) treatment received GnRH on day 6 of the oestrous cycle, PGF(2alpha) 7 days later, and were inseminated at detected oestrus. The remaining cows were subjected to the Ovsynch (OVS) protocol (day 0 GnRH, day 7 PGF(2alpha), day 9 GnRH, and timed artificial insemination (AI) 12 h later) starting on day 3 (OVS3) or day 6 (OVS6 and OVS6E) of the oestrous cycle. Cows in the OVS6E treatment received an injection of 0.5 mg oestradiol cypionate 36 h before AI. Ovaries were examined by ultrasonography and blood was sampled for progesterone and OE(2) concentrations. Uteri were flushed 6 days after AI and recovered embryos-oocytes evaluated. Diameter of the ovulatory follicle at AI differed (P<0.01) among treatments, and it was the largest for OVS3 cows, which also had extended (P<0.01) length of follicular dominance. During proestrus, OD and OVS6E cows had increased (P<0.01) OE(2) concentrations. Fertilization was not altered by treatments, and maximum fertilization was achieved when the number of accessory spermatozoa was >7. Proportions of viable embryos in relation to embryos and embryos-oocytes recovered were smaller for OVS3 cows (P<0.01) than the other treatments, and embryos from OVS3 cows also had fewer (P<0.01) blastomeres and tended (P=0.09) to have a lower proportion of live blastomeres. Extending the period of follicle dominance did not alter fertilization but reduced (P<0.001) embryo quality. Embryo quality was compromised even when the dominance of the ovulatory follicle was extended by only 1.5 days.
authors.affiliation: School of Veterinary Medicine, University of California, Davis, California 95616, USA.
authors.forename: Ronaldo L A
authors.initials: RL
authors.lastname: Cerri
authors.forename: Heloísa M
authors.initials: HM
authors.lastname: Rutigliano
authors.forename: Ricardo C
authors.initials: RC
authors.lastname: Chebel
authors.forename: José E P
authors.initials: JE
authors.lastname: Santos
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000097:blood; D002417:Cattle; D003612:Dairying; D015237:Dinoprost / Q000008:administration & dosage; D004334:Drug Administration Schedule; D004958:Estradiol / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000097:blood; D030762:Estrous Cycle / Q000187:drug effects; D004973:Estrus Synchronization / Q000187:drug effects*; D005260:Female; D005300:Fertility Agents, Female / Q000008:administration & dosage*; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage; D007315:Insemination, Artificial; D007774:Lactation; D008297:Male; D006080:Ovarian Follicle / Q000000981:diagnostic imaging / Q000187:drug effects* / Q000378:metabolism; D010053:Ovary / Q000000981:diagnostic imaging / Q000187:drug effects* / Q000378:metabolism; D010060:Ovulation / Q000187:drug effects*; D010062:Ovulation Induction / Q000662:veterinary*; D011247:Pregnancy; D018873:Pregnancy Rate; D011374:Progesterone / Q000097:blood; D013997:Time Factors; D014463:Ultrasonography
chemical_list: D015415:Biomarkers; D005300:Fertility Agents, Female; D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D004958:Estradiol; C007630:estradiol 17 beta-cypionate; D015237:Dinoprost