title: Social cues can play a role in timing onset of the breeding season of the ewe.
abstract: Female Suffolk sheep were pinealectomized around the vernal equinox to eliminate the major environmental input to the reproductive system (photoperiod) and then either isolated from, or maintained with, pineal-intact gonad-intact sheep. The ewes were ovariectomized and treated with constant-release oestradiol implants and reproductive state was monitored by measuring serum LH concentrations. Pinealectomized ewes that were isolated from the normal flock showed a 2 1/2-month delay in onset of the seasonal rise in LH values compared with that of pineal-intact controls (18 November vs 5 September). On the other hand, pinealectomized ewes that were maintained with the flock showed an onset of the seasonal rise in LH that was not delayed. These results suggest a timekeeping role for social cues for timing onset of the breeding season in an animal that normally relies on photoperiodic signals for temporal regulation of the seasonal reproductive cycle.
authors.affiliation: Reproductive Sciences Program, University of Michigan, Ann Arbor 48109.
authors.forename: N L
authors.initials: NL
authors.lastname: Wayne
authors.forename: B
authors.initials: B
authors.lastname: Malpaux
authors.forename: F J
authors.initials: FJ
authors.lastname: Karsch
mesh_terms: D000818:Animals; D005260:Female; D007986:Luteinizing Hormone / Q000097:blood; D010052:Ovariectomy; D010870:Pineal Gland / Q000601:surgery; D012098:Reproduction; D012621:Seasons; D012756:Sheep / Q000502:physiology*; D012919:Social Behavior
chemical_list: D007986:Luteinizing Hormone