title: Circadian variation in ghrelin and certain stress hormones in crib-biting horses.
abstract: Crib-biting is classified as an oral stereotypy, which may be initiated by stress susceptibility, management factors, genetic factors and gastrointestinal irritation. Ghrelin has been identified in the gastric mucosa and is involved in the control of food intake and reward, but its relationship to crib-biting is not yet known. The aim of this study was to examine the concentration and circadian variation of plasma ghrelin, cortisol, adrenocorticotropic hormone (ACTH) and β-endorphin in crib-biting horses and non-crib-biting controls. Plasma samples were collected every second hour for 24h in the daily environment of eight horses with stereotypic crib-biting and eight non-crib-biting controls. The crib-biting horses had significantly higher mean plasma ghrelin concentrations than the control horses. The circadian rhythm of cortisol was evident, indicating that the sampling protocol did not inhibit the circadian regulation in these horses. Crib-biting had no statistically significant effect on cortisol, ACTH or β-endorphin concentrations. The inter-individual variations in β-endorphin and ACTH were higher than the intra-individual differences, which made inter-individual comparisons difficult and complicated the interpretation of results. Further research is therefore needed to determine the relationship between crib-biting and ghrelin concentration.
authors: University of Helsinki, Faculty of Veterinary Medicine, Department of Equine and Small Animal Medicine, Koetilantie 7, P.O. Box 57, 00014 Helsinki, Finland. karin.hemmann@helsinki.fi
authors: Karin
authors: K
authors: Hemmann
authors: Marja
authors: M
authors: Raekallio
authors: Kira
authors: K
authors: Kanerva
authors: Laura
authors: L
authors: Hänninen
authors: Matti
authors: M
authors: Pastell
authors: Mari
authors: M
authors: Palviainen
authors: Outi
authors: O
authors: Vainio
mesh_terms: D000818:Animals; D002940:Circadian Rhythm; D005260:Female; D054439:Ghrelin / Q000097:blood*; D006736:Horses / Q000502:physiology*; D006854:Hydrocortisone / Q000097:blood*; D008297:Male; D011333:Pro-Opiomelanocortin / Q000097:blood*; D013239:Stereotyped Behavior; D013312:Stress, Physiological
chemical_list: D054439:Ghrelin; D011333:Pro-Opiomelanocortin; D006854:Hydrocortisone