title: Lengthened superstimulatory treatment in cattle: Evidence for rescue of follicles within a wave rather than continuous recruitment of new follicles.
abstract: A study was designed to compare the effects of a conventional (4 days) versus a lengthened (7 days) superstimulation protocol on follicle dynamics and to test the hypothesis that superstimulatory treatment only rescues small follicles within the wave. Nonlactating beef cows received a progesterone-releasing intravaginal device [PRID] and were superstimulated with 400-mg FSH on the day of follicle ablation-induced wave emergence (Day 0). The control group (n = 5) received FSH over 4 days, whereas the long group (n = 5) received FSH over 7 days. PGF was administered twice on Day 2 (control group) or 5 (long group), and PRIDs were removed 24 hours after the first PGF. Cows received 25-mg LH 24 hours after PRID removal. The cows chosen for the present study represented a subset from a larger group of 24 cows in which superovulation results were obtained and published. Cows in the present study were those with the lowest antral follicle counts at the time of wave emergence in order to facilitate tracking of individual follicles. Daily ultrasonographic examinations monitored follicle diameters and numbers. A reduction (P < 0.01) in the number of 1- to 2-mm follicles from Day 0 to the end of the superstimulatory treatment was associated with a progressive shift to the next size category in both groups. On the day of LH treatment, the number of follicles in any size category did not differ between groups. The number of follicles of diameter 5 mm or less decreased during superstimulation (i.e., no continuous recruitment of small follicles; P < 0.001), and the number of follicles of diameter 1 mm or greater at the end of superstimulation did not differ from that at the beginning of superstimulation (P = 0.739). However, the total number of follicles of diameter 3 mm or greater at the end was greater than the number of follicles of diameter 3 mm or greater at the beginning of superstimulation because of growth of the 1- to 2-mm population during treatment (P < 0.001). Follicle growth was slower in the long group than in the control group. Results support the hypothesis that both 4-day and 7-day superstimulatory protocols rescue small antral follicles present at the time of wave emergence; there was no evidence for continuous recruitment of new follicles. Results also provide rationale for the hypothesis that a lengthened treatment protocol is associated with greater follicle maturation and capacity to ovulate.
authors.affiliation: Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
authors.forename: A
authors.initials: A
authors.lastname: García Guerra
authors.affiliation: Instituto de Reproducción Animal Córdoba, Córdoba, Argentina.
authors.forename: A
authors.initials: A
authors.lastname: Tribulo
authors.affiliation: Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Yapura
authors.affiliation: Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
authors.forename: G P
authors.initials: GP
authors.lastname: Adams
authors.affiliation: Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Singh
authors.affiliation: Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada. Electronic address: reuben.mapletoft@usask.ca.
authors.forename: R J
authors.initials: RJ
authors.lastname: Mapletoft
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D004624:Embryo Transfer / Q000662:veterinary; D004973:Estrus Synchronization / Q000187:drug effects; D005260:Female; D005640:Follicle Stimulating Hormone / Q000494:pharmacology; D006080:Ovarian Follicle / Q000000981:diagnostic imaging / Q000187:drug effects*; D010062:Ovulation Induction / Q000379:methods / Q000662:veterinary*; D013480:Superovulation / Q000187:drug effects*; D013997:Time Factors; D014463:Ultrasonography
chemical_list: D005640:Follicle Stimulating Hormone
keywords: FSH; Follicular growth; Follicular wave; Gonadotropin; Superovulation