title: Effects of follicular status at treatment on follicular development and ovulation in response to FSH in Spanish merino ewes.
abstract: Cyclic Spanish Merino ewes were treated on Day 13 of the estrous cycle with 12 mg, i.m., FSH-P in saline (n = 9) or propylene glycol (n = 24), currently with 100 micrograms, i.m., Cloprostenol (Day 0). From Day-6 to Day 0, the ewes were observed daily by transrectal ultrasonography, after Day 0, ultrasonography was performed every 12 h for 72 h. Sizes and locations of > or = 2 mm follicles were recorded at each observation. The ovulation rate was determined by laparoscopy on Day 7 after estrus. The number of ovulations ranged from 0 to 6 in ewes treated with FSH-P in saline and from 0 to 16 in ewes receiving FSH-P in propylene glycol (P < 0.05). In the latter group, the response was bimodally distributed; about half of the females had 1 ovulation, whereas the remainder had > 4 with a mean of 7 ovulations. The ovulation rate was associated with 2 characteristics of the largest follicle present at treatment (Day 0). First, if the largest follicle on Day 0 had not changed in diameter from Day-1 to Day 0, then 7 of 9 ewes had > 3 ovulations; if the largest follicle had either increased or decreased, only 8 of 24 ewes had > 3 ovulations (P < 0.05). Second, there was a linear trend (P < 0.07) for ovulation rate to decrease as the persistence of the largest follicle at treatment increased; no ewe in which the largest follicle on Day 0 remained present for more than 36 h ovulated more than 6 follicles. As with the ovulation rate, the numbers of large follicles on Days 1.5, 2 and 2.5 varied with the interaction of change in diameter of the largest follicle on Day 0 from Day-1 to Day 0 and with vehicle. In summary, the superovulatory response was affected by the change in diameter from Day-1 to Day 0 of the largest follicle on Day 0 and the period required for that follicle to regress after treatment with FSH-P and cloprostenol.
authors.affiliation: Departamento de Reproducción Animal y Conservación de Recursos Zoogenéticos SGIT/INIA, Madrid, Spain.
authors.forename: A
authors.initials: A
authors.lastname: López Sebastián
authors.forename: A
authors.initials: A
authors.lastname: González de Bulnes
authors.forename: J
authors.initials: J
authors.lastname: Santiago Moreno
authors.forename: A
authors.initials: A
authors.lastname: Gómez Brunet
authors.forename: E C
authors.initials: EC
authors.lastname: Townsend
authors.forename: E K
authors.initials: EK
authors.lastname: Inskeep
mesh_terms: D000818:Animals; D003008:Cloprostenol / Q000494:pharmacology; D004971:Estrus / Q000187:drug effects / Q000502:physiology; D005260:Female; D005640:Follicle Stimulating Hormone / Q000494:pharmacology*; D008297:Male; D006080:Ovarian Follicle / Q000166:cytology* / Q000000981:diagnostic imaging / Q000187:drug effects; D010060:Ovulation / Q000187:drug effects*; D012756:Sheep; D013030:Spain; D014463:Ultrasonography
chemical_list: D003008:Cloprostenol; D005640:Follicle Stimulating Hormone