Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh EH25 9RG, UK.
Vet J. 2012 Jul;193(1):81-6. doi: 10.1016/j.tvjl.2011.09.030. Epub 2011 Dec 16.
Without effective pain relief, rubber ring castration of lambs is acutely painful and can also produce chronic pain. The potential of novel, smaller rubber rings to reduce this pain substantially has been investigated. Three groups of eight 2-3 day old lambs, were castrated either with conventional rubber rings (cRR), or novel smaller rubber rings without (nRR) and with local anaesthetic treatment (nRR+La). Behavioural responses and chronic lesions indicative of pain were compared. No major reductions in behavioural responses were produced by castration with nRRs compared with cRRs, but injection of local anaesthetic did reduce these responses significantly. Lambs in all groups developed chronic inflammatory lesions but behavioural evidence of chronic pain was rarely seen. After 28 days, 6/8 necrotic scrotums had been shed by nRR+La; 4/8 by nRR and 2/8 by cRR lambs. The dimensions of rubber rings on necrotic scrotums, suggest that cRRs contracted to their un-stretched size before being shed, whereas nRRs did not. It is concluded that neither of these rubber rings exerted sufficient pressure on trapped nerves to produce anaesthesia rapidly and this may be explained by the physical properties of the tissues at the neck of the scrotum which support the ring.
如果没有有效的止痛措施，用橡胶环对羔羊进行去势会非常痛苦，而且还可能产生慢性疼痛。因此，人们研究了新型较小尺寸的橡胶环来大幅减轻这种疼痛。将三组各 8 只 2-3 天大的羔羊分别用传统橡胶环（cRR）、新型较小尺寸的无（nRR）和有局部麻醉剂处理的橡胶环（nRR+La）进行去势。比较了行为反应和慢性疼痛指示病变。与 cRR 相比，用 nRR 去势对行为反应的减少作用不大，但注射局部麻醉剂可显著减少这些反应。所有组的羔羊都出现了慢性炎症性病变，但很少有慢性疼痛的行为证据。28 天后，nRR+La 组有 6/8 只坏死阴囊脱落；nRR 组有 4/8 只，cRR 组有 2/8 只。坏死阴囊上橡胶环的尺寸表明，cRR 在脱落前收缩到未拉伸的尺寸，而 nRR 则没有。因此，这些橡胶环都没有对被困的神经施加足够的压力来迅速产生麻醉效果，这可能是由于阴囊颈部的组织的物理特性支持了这种情况。
