title: Ovarian superstimulation after follicular wave synchronization with GnRH at two different stages of the estrous cycle in cattle.
abstract: The objective of this study was to evaluate superovulatory programs based on synchronization of follicular waves with GnRH at 2 different stages of the estrous cycle. Sixteen Holstein cows were randomly assigned to 1 of 3 groups and administered GnRH (Cystorelin, 4 ml i.m.) between Days 4 and 7 (Groups 1 and 3) or between Days 15 and 18 (Group 2) of the estrous cycle (estrus = Day 0). Four days after GnRH treatment, > or = 7-mm follicles were punctured in Groups 1 (n = 6) and 2 (n = 6) or were left intact in Group 3 (n = 4). All cows were superstimulated 2 d later (i.e., from Days 6 to 10 after GnRH treatment) with a total of 400 mg NIH-FSH (Folltropin-V) given twice daily in decreasing doses. The GnRH treatment caused a rapid disappearance of large follicles (P < 0.005), rapid decrease in estradiol concentrations (P < 0.003), and increase in the number of recruitable follicles (4 to 6 mm; P < 0.04), indicative of the emergence of a new follicular wave within 3 to 4 d of treatment. Between 4 and 6 d after GnRH treatment, the mean number of 4- to 6-mm follicles decreased (4.7 +/- 1.8 to 1.5 +/- 3.3) in the nonpunctured group but increased (3.9 +/- 1.0 to 7.3 +/- 1.9) in the punctured group of cows (P < 0.05). In response to FSH treatment, the increase in the number of > or = 7-mm follicles was delayed by approximately 2 d in the nonpunctured group (P < 0.006). Moreover, the mean number of > or = 7-mm follicles at estrus was higher (16.9 +/- 1.7 vs 11.5 +/- 3.0; P < 0.1) in the punctured than the nonpunctured group. The increase in progesterone concentration after estrus was delayed in the nonpunctured group (P < 0.1) compared with the punctured follicles. Mean numbers of CL as well as freezable (Grade 1 and 2) and transferable (Grade 1, 2 and 3) embryos were similar (P > 0.1) in punctured and nonpunctured groups. Spontaneous estrus did not occur prior to cloprostenol-induced luteolysis in any group, and stage of the estrous cycle during which GnRH was given did not affect (P > 0.1) hormonal and follicular responses in the punctured groups. In conclusion, GnRH given at different stages of the estrous cycle promotes the emergence of a follicular wave at a predictable time. Puncture of the newly formed dominant follicle increases the number of recruitable follicles (4 to 6 mm) 2 d later and, in response to superstimulation with FSH, causes a greater number and faster entry of recruitable follicles into larger classes (> or = 7 mm) and a faster postovulatory increase in progesterone concentrations.
authors.affiliation: Centre de Recherche en Biologie de la Reproduction, Département des Sciences Animales Université Laval, Ste-Foy, Québec.
authors.forename: H
authors.initials: H
authors.lastname: Kohram
authors.forename: H
authors.initials: H
authors.lastname: Twagiramungu
authors.forename: D
authors.initials: D
authors.lastname: Bousquet
authors.forename: J
authors.initials: J
authors.lastname: Durocher
authors.forename: L A
authors.initials: LA
authors.lastname: Guilbault
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D003008:Cloprostenol / Q000627:therapeutic use; D004958:Estradiol / Q000097:blood; D004971:Estrus; D004973:Estrus Synchronization / Q000187:drug effects; D005260:Female; D005640:Follicle Stimulating Hormone / Q000502:physiology; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology* / Q000502:physiology; D007315:Insemination, Artificial / Q000662:veterinary; D016018:Least-Squares Analysis; D008297:Male; D015999:Multivariate Analysis; D006080:Ovarian Follicle / Q000000981:diagnostic imaging / Q000187:drug effects / Q000502:physiology*; D011374:Progesterone / Q000097:blood; D011677:Punctures / Q000662:veterinary; D011863:Radioimmunoassay / Q000662:veterinary; D011897:Random Allocation; D013480:Superovulation; D014463:Ultrasonography
chemical_list: D007987:Gonadotropin-Releasing Hormone; D003008:Cloprostenol; D011374:Progesterone; D004958:Estradiol; D005640:Follicle Stimulating Hormone