Conditioned place preference reveals ongoing pain in calves 3 weeks after disbudding

The authors initiated a retraction over concerns relating to irregularities found in the raw data. Concerns relating to the data can be found in the retraction notice: https://www.nature.com/articles/s41598-025-88692-z

Hot-iron disbudding, a routine procedure that prevents horn bud growth through cauterization, is painful for calves. The resulting burns remain sensitive to touch for weeks, but it is unknown whether calves experience ongoing, non-evoked pain. We evaluated conditioned place preference for analgesia in 44 calves disbudded or sham-disbudded 6 hours (Day 0) or 20 days (Day 20) before testing (n = 11/treatment). Calves were conditioned to associate the effects of a lidocaine cornual nerve block with the location and pattern of a visual stimulus, and a control injection of saline with the contrasting stimulus. On Day 0, disbudded calves tended to prefer the lidocaine-paired stimulus over the saline-paired one, suggesting that they found analgesia rewarding. On Day 20, sham calves avoided the lidocaine-paired stimulus, consistent with humans’ experience of this drug being painful. Disbudded calves on Day 20 did not show this aversion, suggesting that they traded off the short-term pain of the lidocaine with the longer-term analgesia provided. Day 0 sham calves did not avoid the lidocaine-paired stimulus, likely because they received less than half the dose of Day 20 calves during conditioning. Thus, higher doses of lidocaine are aversive to uninjured animals, but disbudded calves are willing to engage in this cost. We conclude that calves experience ongoing pain 3 weeks after disbudding, raising additional welfare concerns about this procedure.

Methods
These details are provided in the orginal article, but please note that this has been retracted.

作者因原始数据存在异常相关疑虑启动了撤稿流程。有关该数据的具体疑虑可查阅撤稿公告：https://www.nature.com/articles/s41598-025-88692-z

热铁烙去角术（Hot-iron disbudding）是通过烙灼手段阻止犊牛角芽生长的常规操作，但该操作会给犊牛带来疼痛。术后形成的灼伤创面在数周内仍对触碰敏感，但目前尚不明确犊牛是否会持续出现非诱发性疼痛。本研究针对44头犊牛开展了镇痛条件位置偏好实验：受试犊牛分别在实验前6小时（第0天）或20天（第20天）接受热铁烙去角术或假去角术，每组处理方式对应11头犊牛（n=11/处理组）。实验前，将犊牛接受利多卡因（lidocaine）角神经阻滞的效应与某一视觉刺激的位置和样式建立关联，同时将生理盐水对照注射与另一对比视觉刺激建立关联。在第0天，接受去角术的犊牛更倾向于选择与利多卡因配对的视觉刺激，而非生理盐水配对的刺激，这表明犊牛认为镇痛效果具有奖赏性。第20天时，假去角组犊牛会回避与利多卡因配对的刺激，这与人类使用该药物时产生痛感的体验相符；而同日接受去角术的犊牛未表现出此类回避行为，表明它们会权衡利多卡因带来的短期疼痛与后续获得的长期镇痛效果。第0天的假去角组犊牛并未回避利多卡因配对的刺激，这可能是因为在条件化训练阶段，该组犊牛的给药剂量仅为第20天组犊牛的一半以下。由此可见，高剂量利多卡因会对未受损伤的动物产生厌恶性，但接受过去角术的犊牛愿意承担此类代价。本研究最终得出结论：犊牛在接受热铁烙去角术后3周仍会持续感受到疼痛，这为该操作的动物福利问题增添了新的担忧。

方法 相关细节详见原文，但请注意该文章已被撤稿。