title: Ovarian follicular wave synchronization and induction of ovulation in postpartum beef cows.
abstract: An experiment was designed to evaluate a) the effect of a progesterone-estradiol combined treatment on ovarian follicular dynamics in postpartum beef cows, and b) ovulation and the subsequent luteal activity after short-term calf removal and GnRH agonist treatment. Multiparous Angus cows (25 to 40 d after calving) were assigned to the following treatments: untreated (Control, n = 9); short term calf removal (CR, n = 8); progesterone (CIDR, n = 9) and progesterone plus estradiol-17 beta (CIDR + E-17 beta, n = 9). Progesterone treatment (CIDR) lasted 8 d and the day of device insertion was considered as Day 0. Cows in the CIDR + E-17 beta group also received an i.m. injection of 5 mg of E-17 beta on Day 1. On Day 8, calves were removed for 48 h (CR, CIDR and CIDR + E-17 beta groups) and 6 h before the end of calf removal these cows also received an i.m. injection of 8 micrograms of Busereline (GnRH). Anestrus was confirmed in all cows by the absence of luteal tissue and progesterone concentrations below 1 ng ml-1 at the beginning of the experiment. Although mean (+/- SEM) interval from the beginning of the experiment (Day 0) to wave emergence did not differ (P > 0.05) among treatment groups (Control, 1.9 +/- 1.0, range -2 to 7 d; CR, 3.9 +/- 0.7, range 0 to 6 d; CIDR, 2.8 +/- 0.5, range 0 to 4 d and CIDR + E-17 beta, 4.1 +/- 0.2, range 3 to 5), the variability was less (P < 0.05) in the CIDR + E-17 beta group. The proportion of cows ovulating 24 to 48 h after GnRH administration tended (P = 0.08) to be higher in cows from CIDR + E-17 beta group (8/9) than in those of CR (5/8) or CIDR (6/9) groups, respectively and was associated with a higher proportion (P < 0.05) of CIDR + E-17 beta treated cows (9/9) that had a dominant follicle in the growing/early static phase at the time of GnRH treatment compared to the other GnRH treated groups (5/8, and 4/9 for CR and CIDR groups, respectively). Two CR cows ovulated 0-24 h after GnRH and only one Control cow ovulated the day before the time of GnRH administration. Cows pretreated with progesterone had longer (P < 0.05) luteal lifespan (CIDR, 14.5 +/- 0.7, CIDR + E-17 beta, 13.9 +/- 0.6 d) than those not treated with CIDR (Control, 5, CR, 4.0 +/- 0.4). We conclude that progesterone plus estradiol treatment results in tightly synchronized wave emergence and high GnRH-induced ovulation rate with normal luteal activity in postpartum beef cattle.
authors.affiliation: Departamento de Reproducción Animal, Facultad de Agronomía y Veterinaria, Universidad Nacional de Río Cuarto, Argentina.
authors.forename: G M
authors.initials: GM
authors.lastname: Rivera
authors.forename: C G
authors.initials: CG
authors.lastname: Goñi
authors.forename: M A
authors.initials: MA
authors.lastname: Chaves
authors.forename: S B
authors.initials: SB
authors.lastname: Ferrero
authors.forename: G A
authors.initials: GA
authors.lastname: Bo
mesh_terms: D000282:Administration, Intravaginal; D000780:Anestrus; D000818:Animals; D000833:Animals, Suckling; D001835:Body Weight; D002064:Buserelin / Q000627:therapeutic use; D002417:Cattle / Q000502:physiology*; D003338:Corpus Luteum / Q000000981:diagnostic imaging / Q000502:physiology; D004958:Estradiol / Q000627:therapeutic use; D004973:Estrus Synchronization / Q000187:drug effects / Q000502:physiology*; D005260:Female; D005300:Fertility Agents, Female / Q000627:therapeutic use; D006080:Ovarian Follicle / Q000000981:diagnostic imaging / Q000502:physiology*; D010062:Ovulation Induction / Q000379:methods / Q000662:veterinary*; D049590:Postpartum Period; D011374:Progesterone / Q000097:blood / Q000627:therapeutic use; D011863:Radioimmunoassay / Q000662:veterinary; D018709:Statistics, Nonparametric; D014463:Ultrasonography
chemical_list: D005300:Fertility Agents, Female; D011374:Progesterone; D004958:Estradiol; D002064:Buserelin