title: Endogenous circannual cycles of ovarian activity and changes in prolactin and melatonin secretion in wild and domestic female sheep maintained under a long-day photoperiod.
abstract: The present study examines the ovulatory activity of wild and domesticated ewes subjected to either a constant photoperiod of long days (16L:8D) or natural changes in daily photoperiod for 16 mo. The aim was to determine whether an endogenous reproductive rhythm controls seasonal reproductive activity in these sheep, and how the photoperiod might affect this. The effects of long-day photoperiods on long-term changes in prolactin and melatonin secretion were also evaluated. The two species showed changes in reproductive activity under the constant photoperiod conditions, suggesting the existence of an endogenous rhythm of reproduction. This rhythm was differently expressed in the two types of ewe (P < 0.05), with the domestic animals exhibiting much greater sensitivity to the effects of long days. A circannual rhythm of plasma prolactin concentration was also seen in both species and under both photoperiod conditions, although in both species the amplitude was always lower in the long-day animals (P < 0.01). The duration of the nocturnal melatonin plasma concentrations reflected the duration of darkness in both species and treatments. The peak melatonin concentration did not differ between seasons either under natural or long-day photoperiods.
authors.affiliation: Departamento de Reproducción Animal, Instituto Nacional de Investigaciones Agrarias, SGIT-INIA, Madrid, Spain. gomez@inia.es
authors.forename: Amelia
authors.initials: A
authors.lastname: Gómez-Brunet
authors.forename: Julián
authors.initials: J
authors.lastname: Santiago-Moreno
authors.forename: Ana
authors.initials: A
authors.lastname: del Campo
authors.forename: Benoit
authors.initials: B
authors.lastname: Malpaux
authors.forename: Philippe
authors.initials: P
authors.lastname: Chemineau
authors.forename: Domingo J
authors.initials: DJ
authors.lastname: Tortonese
authors.forename: Antonio
authors.initials: A
authors.lastname: Gonzalez-Bulnes
authors.forename: Antonio
authors.initials: A
authors.lastname: López-Sebastián
mesh_terms: D000818:Animals; D000829:Animals, Domestic / Q000502:physiology; D000835:Animals, Wild / Q000502:physiology; D005260:Female; D008550:Melatonin / Q000378:metabolism*; D010053:Ovary / Q000378:metabolism* / Q000502:physiology; D017440:Photoperiod; D011388:Prolactin / Q000378:metabolism*; D012098:Reproduction / Q000502:physiology; D012621:Seasons; D012756:Sheep / Q000502:physiology*; D013997:Time Factors
chemical_list: D011388:Prolactin; D008550:Melatonin