title: Challenges of thermal nociceptive threshold testing in the donkey.
abstract: OBJECTIVE
  To evaluate a thermal nociceptive threshold (TNT) testing device in the donkey, and the influence of potential confounding factors on TNTs.
  
  
  METHODS
  Two groups (Group 1 and Group 2) of eight castrated male donkeys aged 4-9 years, weighing 105-170 kg.
  
  
  METHODS
  TNTs were measured by heating a thermal probe on skin until an end-point behaviour (threshold temperature) or a cut-out temperature (51 °C) was reached. The withers and the dorsal aspect of the distal limb were used as sites for TNT testing. The effects on TNT of different confounding factors: the limb tested; rate of heating; and ambient temperature were evaluated. Data were analyzed using general linear models, and Mann-Whitney tests, p < 0.05 was considered significant.
  
  
  RESULTS
  End-point behaviours (skin twitch or donkey looking at test device) when the thermal probe heated the withers were observed in approximately half of tests. TNT was (mean ± SD) 46.8 ± 2.85 °C. Subsequently the limb was evaluated as the test site in Group 1 followed by Group 2 donkeys; end-point behaviour being a foot-lift. In Group 1, 72% of tests ended in an end-point behaviour but the response rate was lower in Group 2 (20%), although TNTs were similar [(47.6 ± 3.3) and (47.3 ± 3.0) °C respectively] for responding animals. Rate of heating, ambient temperature and laterality (right or left) did not affect thresholds, but mean TNT was significantly higher in the forelimb (48.5 ± 2.8 °C) than the hind limb (47.4 ± 2.8 °C) (p = 0.012).
  
  
  CONCLUSIONS
  When a thermal probe cut-out temperature of 51 °C was used in TNT testing in the donkey a high proportion of tests did not produce an identifiable end point behaviour. Higher cut-out temperatures damaged the skin. Under these conditions, thermal nociceptive threshold testing appears not be an appropriate analgesiometry technique in the donkey.
  
  
  CONCLUSIONS
  TNT testing under these conditions is not suitable form of analgesiometry for donkeys.
authors.affiliation: Ross University School of Veterinary Medicine, St Kitts, West Indies; Animal Welfare and Behaviour Group, University of Bristol, Bristol, UK.
authors.forename: Nicola J
authors.initials: NJ
authors.lastname: Grint
authors.forename: Helen R
authors.initials: HR
authors.lastname: Whay
authors.forename: Thierry
authors.initials: T
authors.lastname: Beths
authors.forename: Kathy
authors.initials: K
authors.lastname: Yvorchuk
authors.forename: Joanna C
authors.initials: JC
authors.lastname: Murrell
mesh_terms: D000818:Animals; D018397:Equidae / Q000502:physiology*; D006358:Hot Temperature; D008297:Male; D059225:Nociception / Q000502:physiology; D010147:Pain Measurement / Q000662:veterinary; D017288:Pain Threshold / Q000502:physiology*; D012879:Skin Physiological Phenomena
keywords: donkey; equine; nociceptive threshold testing; thermal