title: The physiological consequences of crib-biting in horses in response to an ACTH challenge test.
abstract: Stereotypies are repetitive and relatively invariant patterns of behavior, which are observed in a wide range of species in captivity. Stereotypic behavior occurs when environmental demands produce a physiological response that, if sustained for an extended period, exceeds the natural physiological regulatory capacity of the organism, particularly in situations that include unpredictability and uncontrollability. One hypothesis is that stereotypic behavior functions to cope with stressful environments, but the existing evidence is contradictory. To address the coping hypothesis of stereotypies, we triggered physiological reactions in 22 horses affected by stereotypic behavior (crib-biters) and 21 non-crib-biters (controls), using an ACTH challenge test. Following administration of an ACTH injection, we measured saliva cortisol every 30 min and heart rate (HR) continuously for a period of 3h. We did not find any differences in HR or HR variability between the two groups, but crib-biters (Group CB) had significantly higher cortisol responses than controls (Group C; mean ± SD: CB, 5.84 ± 2.62 ng/ml, C, 4.76 ± 3.04 ng/ml). Moreover, crib-biters that did not perform the stereotypic behavior during the 3-hour test period (Group B) had significantly higher cortisol levels than controls, which was not the case of crib-biters showing stereotypic behavior (Group A) (B, 6.44 ± 2.38 ng/ml A, 5.58 ± 2.69 ng/ml). Our results suggest that crib-biting is a coping strategy that helps stereotypic individuals to reduce cortisol levels caused by stressful situations. We conclude that preventing stereotypic horses from crib-biting could be an inappropriate strategy to control this abnormal behavior, as it prevents individuals from coping with situations that they perceive as stressful.
authors.affiliation: Agroscope, Swiss National Stud Farm, Avenches, Switzerland. Electronic address: sabrina.briefer@agroscope.admin.ch.
authors.forename: S
authors.initials: S
authors.lastname: Briefer Freymond
authors.affiliation: Agroscope, Swiss National Stud Farm, Avenches, Switzerland.
authors.forename: D
authors.initials: D
authors.lastname: Bardou
authors.affiliation: Institute of Agricultural Sciences, ETH Zurich, Switzerland.
authors.forename: E F
authors.initials: EF
authors.lastname: Briefer
authors.affiliation: Veterinary Physiology, Vetsuisse-Faculty, University of Bern, Switzerland.
authors.forename: R
authors.initials: R
authors.lastname: Bruckmaier
authors.affiliation: Swiss Institute of Equine Medicine (ISME), Agroscope and University of Bern, Switzerland.
authors.forename: N
authors.initials: N
authors.lastname: Fouché
authors.affiliation: Agroscope, Swiss National Stud Farm, Avenches, Switzerland.
authors.forename: J
authors.initials: J
authors.lastname: Fleury
authors.affiliation: Agroscope, Swiss National Stud Farm, Avenches, Switzerland.
authors.forename: A-L
authors.initials: AL
authors.lastname: Maigrot
authors.affiliation: Swiss Institute of Equine Medicine (ISME), Agroscope and University of Bern, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Ramseyer
authors.affiliation: Institute of Biology, University of Neuchâtel, Switzerland; School of Psychology & Neuroscience, University of St Andrews, Scotland, United Kingdom.
authors.forename: K
authors.initials: K
authors.lastname: Zuberbühler
authors.affiliation: Agroscope, Swiss National Stud Farm, Avenches, Switzerland.
authors.forename: I
authors.initials: I
authors.lastname: Bachmann
mesh_terms: D000223:Adaptation, Psychological / Q000187:drug effects / Q000502:physiology*; D000324:Adrenocorticotropic Hormone / Q000008:administration & dosage / Q000378:metabolism*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006728:Hormones / Q000008:administration & dosage / Q000378:metabolism; D006736:Horses / Q000502:physiology* / Q000523:psychology*; D006854:Hydrocortisone / Q000378:metabolism; D008297:Male; D012463:Saliva / Q000378:metabolism; D013239:Stereotyped Behavior / Q000187:drug effects / Q000502:physiology*
chemical_list: D006728:Hormones; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone
keywords: Coping strategy; Stereotypy; Stress physiology