Animal Welfare Program, Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada.
Biol Lett. 2019 Oct 31;15(10):20190642. doi: 10.1098/rsbl.2019.0642. Epub 2019 Oct 30.
Pain in animals is typically assessed using reflexive and physiological responses. These measures allow inferences regarding nociception but provide little basis for conclusions about the affective component of pain (i.e. how negatively the experience is perceived). Calves routinely undergo painful procedures on commercial farms, including hot-iron disbudding, providing a convenient model to study pain in animals. The aim of this study was to investigate the affective component of post-procedural pain due to hot-iron disbudding, using conditioned place aversion. Calves ( = 31) were subjected to two procedures (one bud at a time): one without post-procedural pain control and the other with the use of a nonsteroidal anti-inflammatory drug (either meloxicam ( = 16) or ketoprofen ( = 15)). All procedures included the use of local anaesthesia (lidocaine). Place conditioning was tested 2 days after the last treatment by allowing calves to freely roam between the pens where they had previously been disbudded. Calves spent more time, and lay down more frequently, in the pen where they received meloxicam compared with the pen where they only received a local block. Surprisingly, calves avoided the pen where they received ketoprofen compared with the control treatment pen. We hypothesize that the shorter duration of action of ketoprofen resulted in increasing pain at the end of the conditioning period, explaining the increased aversion to this treatment. These results illustrate the value of place conditioning paradigms to assess the affective component of pain in animals, and suggest that the animal's evaluation of painful events depends upon the time course of when the pain is experienced.
动物的疼痛通常通过反射和生理反应来评估。这些措施可以推断出伤害感受，但对于疼痛的情感成分（即体验的负面程度）几乎没有依据。犊牛在商业农场中经常接受各种疼痛处理程序，包括热铁烙除术，这为研究动物疼痛提供了一个便利的模型。本研究旨在通过条件性位置厌恶来研究热铁烙除术引起的术后疼痛的情感成分。将 31 头犊牛（ = 31）分为两组进行处理（一次一个芽）：一组不进行术后疼痛控制，另一组使用非甾体抗炎药（美洛昔康（ = 16）或酮洛芬（ = 15））。所有程序均包括使用局部麻醉（利多卡因）。在最后一次治疗后 2 天进行位置条件测试，让犊牛自由在之前进行烙除术的围栏之间活动。与仅接受局部阻滞的围栏相比，犊牛在接受美洛昔康的围栏中花费更多的时间，躺下的次数也更多。令人惊讶的是，与对照组相比，犊牛避开了接受酮洛芬的围栏。我们假设酮洛芬的作用持续时间较短，导致在条件作用期间结束时疼痛加剧，这解释了对这种治疗的厌恶增加。这些结果说明了位置条件作用范式在评估动物疼痛的情感成分方面的价值，并表明动物对疼痛事件的评估取决于疼痛发生的时间进程。
