Comparison of methods for the reduction of acute pain produced by rubber ring castration or tail docking of week-old lambs

Behavioural and plasma cortisol changes were recorded for groups of eight SuffolkxGreyface lambs subjected to castration or tail docking using rubber rings with and without local anaesthetic treatment. Immediately after application of the rubber ring, local anaesthetic (2x0.2 ml 2% lignocaine) was administered either by needle and syringe or by high-pressure needleless injection into each side of the neck of the scrotum or tail at the site of the ring, or by high pressure needleless injection into the testes before ring-application. In other groups, the innervation to the scrotum or tail was disabled by crushing with a powered bloodless castrator just proximal to the ring. Measurements were recorded in groups of control (handled) lambs, with and without local anaesthetic treatment. Application of local anaesthetic by high pressure needleless injection had little effect on either plasma cortisol values or behaviour of control lambs. For castration, application of the bloodless castrator and/or local anaesthetic at the ring site reduced the peak plasma cortisol concentration by 50% (P less than or equal to 0.01), the incidence of active behavioural responses by 80 and 64% (P less than or equal to 0.01) respectively, and the time spent in abnormal postures by 68 and 59% (P less than or equal to 0.01) respectively. Both methods were effective in reducing pain for tail docking [active behavioural responses reduced by more than 80% (P less than or equal to 0.01) and abnormal postures by 56% (P less than or equal to 0.01)], although local anaesthetic was more effective, reducing the peak cortisol by 60% (P less than or equal to 0.01) [crushing by 44% (P > 0.05)]. Injection of local anaesthetic into the testes was less effective than injection into the neck of the scrotum at the site of the ring [reduction in abnormal lying postures (P < 0.05), 45 vs 71%, respectively]. The rapid action, effectiveness, and ease of application of these experimental methods may provide the basis for commercially viable methods for reducing the acute pain produced by rubber ring castration and tail docking of lambs.