Abstract
Objective
To evaluate a thermal nociceptive threshold (TNT) testing device in the donkey, and
the influence of potential confounding factors on TNTs.
Animals
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.
Clinical relevance
TNT testing under these conditions is not suitable form of analgesiometry for donkeys.
Keywords
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Article info
Publication history
Accepted:
July 26,
2013
Received:
September 20,
2012
Identification
Copyright
© 2015 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Inc. All rights reserved.
