title: Effect of cohabitation with white-faced ewes on estrous activity of Hampshire and Suffolk ewes exposed to rams in June.
abstract: Two groups of 24 Hampshire and 26 Suffolk purebred ewes each were used to study effects of cohabitation with cyclic white-faced (WF) ewes on estrous activity in June. Ewes lambed in January, February and March and had been isolated from mature rams since the previous fall breeding. From June 1 to July 2, treated (T) ewes were exposed to vasectomized rams and to 65 WF ewes; control (C) ewes were exposed only to vasectomized rams. Ovulation was assessed with biweekly serum progesterone assays; crayon marks were used to detect estrus. Daily observations of ram behavior were conducted to assess sexual activity of rams joined with T and C ewes. Cohabitation with WF ewes increased (P less than .01) ovulation percentages from 46% in C (42% for Hampshires and 50% for Suffolks) to 76% in T ewes (79% for Hampshires and 73% for Suffolks). Mating percentage also was increased (P less than .05) by cohabitation with WF ewes from 14% for C ewes to 30% for T ewes. Rams with T + WF ewes spent more (P less than .05) time checking ewes for estrus than did rams with C ewes. Hence, cohabitation with cycling WF ewes increased ovulation and mating percentages. Many acyclic T ewes first ovulated after 10 or more days of teasing, possibly due to increased ram contact in the presence of WF ewes.
authors.affiliation: Dept. of Anim. Sci. Virginia Polytechnic Institute and State University, Blacksburg 24061-0306.
authors.forename: R A
authors.initials: RA
authors.lastname: Nugent
authors.forename: D R
authors.initials: DR
authors.lastname: Notter
mesh_terms: D000818:Animals; D001947:Breeding; D004971:Estrus / Q000502:physiology*; D005260:Female; D008297:Male; D010060:Ovulation / Q000502:physiology*; D011374:Progesterone / Q000097:blood; D012726:Sexual Behavior, Animal; D012756:Sheep / Q000502:physiology*
chemical_list: D011374:Progesterone