title: The influence of various confounding factors on mechanical nociceptive thresholds in the donkey.
abstract: OBJECTIVE
  To evaluate a mechanical nociceptive threshold (MNT) testing device in the donkey, and to investigate the influence of potential confounders on MNTs generated.
  
  
  METHODS
  Prospective, randomised.
  
  
  METHODS
  Sixteen castrated male donkeys aged 4-9 years, weighing 105-170 kg.
  
  
  METHODS
  Mechanical nociceptive thresholds were measured using an actuator with three pins placed on the dorsal aspect of the distal limb, connected to a force meter. The pins (surface area 15 mm(2) ) were extruded onto the limb by pressurising an air-filled syringe, until the MNT force (when foot-lift was observed) or 25 N (cut-off force) was reached. Effect on MNT of presence of a companion donkey, the limb tested, rate of application of force, testing location, level of distraction, ambient temperature and hair cover at the test site was evaluated. Long and short-term repeatability of MNT was assessed. Data were analysed using general linear models and Mann-Whitney U tests, p < 0.05 was considered significant.
  
  
  RESULTS
  Increasing the rate of force application significantly increased the mean ± SD MNT from 9.2 ± 2.0 N when applied at 0.4 N sec(-1) to 10.6 ± 2.1 N when applied at 1.2 N sec(-1) (p = 0.001). No other factors significantly influenced MNT. Mean MNT remained stable over a 3 week period, however MNTs were significantly (p = 0.006) higher (12.8 ± 3.0 N cf 10.3 ± 1.9 N) after a 12 month interval.
  
  
  CONCLUSIONS
  When designing studies measuring MNT in donkeys, rate of application of force must be standardised. Donkeys' MNTs have good short-term stability suggesting this technique is appropriate for short-term analgesiometry studies; however variability of MNTs over the long-term is greater.
authors.affiliation: School of Veterinary Sciences, University of Bristol, Langford, Bristol, UK.
authors.forename: Nicola J
authors.initials: NJ
authors.lastname: Grint
authors.forename: Thierry
authors.initials: T
authors.lastname: Beths
authors.forename: Kathy
authors.initials: K
authors.lastname: Yvorchuk
authors.forename: Polly M
authors.initials: PM
authors.lastname: Taylor
authors.forename: Mike
authors.initials: M
authors.lastname: Dixon
authors.forename: Helen R
authors.initials: HR
authors.lastname: Whay
authors.forename: Joanna C
authors.initials: JC
authors.lastname: Murrell
mesh_terms: D000818:Animals; D018397:Equidae; D008297:Male; D010147:Pain Measurement / Q000662:veterinary*; D017288:Pain Threshold; D011312:Pressure / Q000009:adverse effects*; D013997:Time Factors
keywords: donkey; equine; mechanical; nociceptive threshold testing