title: Synchronization of follicular wave emergence in the seasonally anestrous ewe: the effects of estradiol with or without medroxyprogesterone acetate.
abstract: Fertility is often lower in anestrous compared to cyclic ewes, after conventional estrus synchronization. We hypothesized that synchronization of ovarian follicular waves and ovulation could improve fertility at controlled breeding in anestrous ewes. Estradiol-17beta synchronizes follicular waves in cattle. The objectives of the present experiments were to study the effect of an estradiol injection, with or without a 12-d medroxyprogesterone acetate (MAP) sponge treatment, on synchronization of follicular waves and ovulation in anestrous ewes. Twenty ewes received sesame oil (n=8) or estradiol-17beta (350 microg; n=12). Eleven ewes received MAP sponges for 12d and were treated with oil (n=5) or estradiol-17beta (n=6) 6d before sponge removal. Saline (n=6) or eCG (n=6) was subsequently given to separate groups of ewes at sponge removal in the MAP/estradiol-17beta protocol. Estradiol treatment alone produced a peak in serum FSH concentrations (4.73+/-0.53 vs. 2.36+/-0.39 ng/mL for treatment vs. control; mean+/-S.E.M.) after a short-lived (6 h) suppression. Six of twelve ewes given estradiol missed a follicular wave around the time of estradiol injection. Medroxyprogesterone acetate-treated ewes given estradiol had more prolonged suppression of serum FSH concentrations (6-18 h) and a delay in the induced FSH peak (32.3+/-3.3 vs. 17.5+/-0.5 h). Wave emergence was delayed (5.7+/-0.3 vs. 1.4+/-0.7d from the time of estradiol injection), synchronized, and occurred at a predictable time (5-7 vs. 0-4d) compared to ewes given MAP alone. All ewes given eCG ovulated 3-4d after injection; this predictable time of ovulation may be efficacious for AI and embryo transfer.
authors.affiliation: Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, Saskatchewan, Canada S7N 5B4.
authors.forename: D M W
authors.initials: DM
authors.lastname: Barrett
authors.forename: P M
authors.initials: PM
authors.lastname: Bartlewski
authors.forename: R
authors.initials: R
authors.lastname: Duggavathi
authors.forename: K L
authors.initials: KL
authors.lastname: Davies
authors.forename: S L
authors.initials: SL
authors.lastname: Huchkowsky
authors.forename: T
authors.initials: T
authors.lastname: Epp
authors.forename: N C
authors.initials: NC
authors.lastname: Rawlings
mesh_terms: D000780:Anestrus / Q000187:drug effects*; D000818:Animals; D004334:Drug Administration Schedule; D004347:Drug Interactions; D004958:Estradiol / Q000008:administration & dosage* / Q000097:blood; D004973:Estrus Synchronization / Q000097:blood / Q000379:methods*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D005498:Follicular Phase / Q000097:blood / Q000187:drug effects* / Q000502:physiology; D007986:Luteinizing Hormone / Q000097:blood; D017258:Medroxyprogesterone Acetate / Q000008:administration & dosage*; D012621:Seasons; D012756:Sheep / Q000502:physiology*; D013997:Time Factors
chemical_list: D004958:Estradiol; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D017258:Medroxyprogesterone Acetate