Validation of a method for assessment of an acute pain in lambs
Publication Type: |
Journal Article |
Year of Publication: |
2002 |
Authors: |
Vince Molony, Joyce E Kent, Iain J McKendrick |
Publication/Journal: |
Applied Animal Behaviour Science |
Keywords: |
animal pain, assessment, behaviour, castration, cortisol, validation |
Abstract:
Acute pain following different methods of rubber ring castration and tail docking (CTD) was assessed using behavioural and physiological methods. Validity was determined by showing how accurately lambs were allocated, to their appropriate treatment groups. Six groups of seven lambs, 5–6 days old, were subjected to treatments, ranked before the experiment, by the amount of tissue damaged and its sensitivity to pain (anaesthesia), in decreasing order of severity. (1) castration and tail docking; (2) bilateral castration; (3) unilateral castration; (4) short scrotum castration; (5) short scrotum castration with local anaesthesia; (6) handled. A further group (n=7) of tail docked only lambs acted as a tail docking control for castration and tail docked lambs. Changes in plasma cortisol concentration; 14 postures and 11 active behaviours were recorded for 180min. Principal component analysis (PCA) and discriminant analysis (DA) helped determine the combinations of indices that most accurately allocated lambs to their appropriate groups. In a PCA, using all individual indices from the lambs, the first two components accounted for 45% of variation in the data. The same indices when used for DA allocated 79% of the lambs to their appropriate group (60min data). Values for 30, 90, 120 and 180min were 50, 55, 48 and 48%, respectively. Measurement was simplified by combining indices: total—incidence of active behaviours, relating to movements of limbs, tail and head plus vocalisation; VSS—time spent dog sitting, lying normally with trembling or with partial extension of hind limbs, and statue standing; V4LL—lying with full extension of the hind limbs; AbS—abnormal standing, excluding statue standing. These combined indices improved accuracy of allocation to 60, 79, 71, 64 and 60% for 30, 60, 90, 120 and 180min. Inclusion of increases in plasma cortisol did not improve the accuracy for 60min data. A simplified index consisting of V4LL and REW (movements of limbs and tail) correctly allocated 74% (60min data, 64% for 30min data). After combining treatment groups, to represent severe, mild or moderate pain the combined indices permitted correct allocation of 91% and the simplified indices 83% of lambs to their appropriate groups (60min data).
It is concluded, that measuring activities involving the limbs and tail and the time spent lying with full extension of the hind limbs for 30–60min, separated the severity of acute pain from the testes, scrotum and tail into six levels with >60% accuracy and into three levels with >80% accuracy. Awareness of these indices and their limitations should improve training for animal pain assessment.