title: Long-term leptin fluctuations in female donkeys.
abstract: BACKGROUND
  The interest in donkeys is growing due to their integration in the systems of ecological farming, among other reasons.
  
  
  OBJECTIVE
  Due to limited reports on leptin concentrations in donkeys, the aim of the present study was to examine age-dependent and seasonal changes in the circulating leptin concentration in female donkeys (jennies) and thus contribute to knowledge about the physiological characteristics of this species.
  
  
  METHODS
  Prospective longitudinal study.
  
  
  METHODS
  The study was performed over a year (September 2008 to September 2009) on 20 yearling and young adult (pregnant, lactating or barren) jennies aged 1-5 years at the onset of the study; the animals were kept on pasture from May to September and stabled for the rest of the year. Blood samples were taken monthly and analysed for serum leptin concentrations by a commercial radioimmunoassay kit.
  
  
  RESULTS
  Circulating leptin concentrations in studied jennies were lower than those reported for donkeys and horses. Despite the tendency for lower values in yearling vs. young adult jennies, the age range of the examined animals was insufficient to confirm any age-related leptin variations. Significant seasonal leptin fluctuations with peak levels in late spring and the lowest levels in autumn months, correlated with photoperiod, were detected in yearling, barren as well as pregnant jennies. Therefore, it was impossible to identify any effects of gestation or lactation on leptin concentrations of jennies.
  
  
  CONCLUSIONS
  The results of this study cannot be used as evidence of a causal relationship between the photoperiod and seasonal circulating leptin fluctuations in donkeys, but could reflect changes induced by various external or internal factors enabling adaptations of grazing animals in variable submediterranean environments.
authors.affiliation: Institute of Physiology, Pharmacology and Toxicology, Veterinary Faculty, University of Ljubljana, Slovenia.
authors.forename: N
authors.initials: N
authors.lastname: Čebulj-Kadunc
authors.affiliation: Centre for Sustained Recultivation Vremščica, Veterinary Faculty, University of Ljubljana, Slovenia.
authors.forename: A
authors.initials: A
authors.lastname: Škibin
authors.affiliation: Clinic for Reproduction and Horses, Veterinary Faculty, University of Ljubljana, Slovenia.
authors.forename: M
authors.initials: M
authors.lastname: Kosec
mesh_terms: D000375:Aging; D000818:Animals; D018397:Equidae / Q000378:metabolism*; D005260:Female; D007774:Lactation; D020738:Leptin / Q000097:blood / Q000378:metabolism*; D017440:Photoperiod; D011247:Pregnancy; D012621:Seasons
chemical_list: D020738:Leptin
keywords: body weight; donkey; horse; leptin; reproduction; seasonal fluctuations