The use of VAS to show the effectiveness of pain reducing techniques on the rubber ring method of castrating and tail docking 2-day old lambs.

Kent et al (2004)

A field trial was conducted to demonstrate that pain resulting from rubber ring castration could be significantly reduced by (1) injecting local anaesthetic with a high-pressure jet injector immediately after the ring was applied or by (2) crushing the nerves from the testes and scrotum with a bloodless castrator. 533 lambs were observed, by a person experienced in assessing pain in lambs, for about two minutes at one point during the first 45 minutes after treatment. The VAS pain assessment was correlated with the objective behavioural measurements made for 30 minutes.

The placebo was 1/100 dilution of local anaesthetic and it appeared to have some 'pain relieving' effect.

Note that both the local anaesthetic and crushing the tissue next to the rings effectively reduced the subjective pain assessment scores.

Scores were 7.0 in rubber ring castrated and docked lambs,  4.0 in placebo rubber ring castrated and docked lambs and less than 2.0 for lambs castrated and docked using rings and local anaesthetic or combined Burdizzo and rubber ring. 

The abnormal activities (REW) and postures of the lambs were also reduced.  VAS correlated with both the incidence of REW (R=0.69) and abnormal posture (V4LL) (r=0.49).