Graphs showing the correlation between the objective behaviour data and the mean VAS of (a) two inexperienced observers and (b) five experienced observers.

Kent et al (2001b)

VAS assessment of pain was made on 37 lambs after observing their behaviour (on video) for six minutes each.  Thirteen people made the observation.  The lambs were split into three clinical pain categories, severe, moderate and mild/no pain groups based on the treatment received.

Lambs in the severe pain group were bilaterally castrated with and without tail docking

Lambs in the moderate pain group were unilaterally or short scrotum castrated

Lambs in the mild / no pain group were either short scrotum castrated with local anaesthetic or untreated control lambs

REW - summation of restlessness (getting up and down), rolling, jumping, foot stamping, kicking, easing quarters and tail wagging over a six minute period 6 to 12 minutes after treatment.

V4LL - is the time spent lying with full extension of the hind legs over the same six minute period as the REW summation was made.

 

(a)  Mean scores of two inexperienced observers.

(neither had any scientific or practical experience of assessing pain in lambs).

These two observers failed to use the full VAS scale and that lambs in all groups, although separated by the objective data, were not separated by these observers.

Note that their VAS scores (in millimetres), for each treatment group cover the same range:- Mild pain (8 to 55) Moderate (9 to 58) Severe (15 to 65).

 

(b) Mean scores of five experienced observers

 (Scientists trained to assess pain in lambs)

These experienced observers used more of the VAS scale and lambs in all groups were separated by these observers.

Note that their VAS scores (in millimetres), for each treatment group cover different ranges:- Mild pain (0 to 9) Moderate (20 to 68) Severe (45 to 88).

The correlation between the VAS of inexperienced observers and the objective data was r = 0.41 versus r = 0.91 for experienced observers.