Animal Welfare Science and Bioethics Centre, School of Veterinary Science, Massey University, Palmerston North, New Zealand.
PLoS One. 2018 Apr 26;13(4):e0196454. doi: 10.1371/journal.pone.0196454. eCollection 2018.
The reliable assessment and management of avian pain is important in the context of animal welfare. Overtly expressed signs of pain vary substantially between and within species, strains and individuals, limiting the use of behaviour in pain studies. Similarly, physiological indices of pain can also vary and may be confounded by influence from non-painful stimuli. In mammals, changes in the frequency spectrum of the electroencephalogram (EEG) recorded under light anaesthesia (the minimal anaesthesia model; MAM) have been shown to reliably indicate cerebral responses to noxious stimuli in a range of species. The aim of the current study was to determine whether the MAM can be applied to the study of nociception in birds. Ten chickens were lightly anaesthetised with halothane and their EEG recorded using surface electrodes during the application of supramaximal mechanical, thermal and electrical noxious stimuli. Spectral analysis revealed no EEG responses to any of these stimuli. Given that birds possess the neural apparatus to detect and process pain, and that the applied noxious stimuli elicit behavioural signs of pain in conscious chickens, this lack of response probably relates to methodological limitations. Anatomical differences between the avian and mammalian brains, along with a paucity of knowledge regarding specific sites of pain processing in the avian brain, could mean that EEG recorded from the head surface is insensitive to changes in neural activity in the pain processing regions of the avian brain. Future investigations should examine alternative electrode placement sites, based on avian homologues of the mammalian brain regions involved in pain processing.
在动物福利的背景下，可靠地评估和管理鸟类疼痛至关重要。明显的疼痛表现因物种、品系和个体而异，限制了行为在疼痛研究中的应用。同样，疼痛的生理指标也可能有所不同，并且可能受到非疼痛刺激的影响。在哺乳动物中，在轻度麻醉下（最小麻醉模型；MAM）记录的脑电图（EEG）频谱的变化已被证明可以可靠地指示对多种物种的有害刺激的大脑反应。本研究的目的是确定 MAM 是否可用于研究鸟类的伤害感受。用氟烷轻度麻醉 10 只鸡，并在施加超最大机械、热和电有害刺激时使用表面电极记录其 EEG。频谱分析显示，这些刺激均未引起 EEG 反应。鉴于鸟类具有检测和处理疼痛的神经装置，并且施加的有害刺激在有意识的鸡中引起疼痛的行为迹象，这种无反应可能与方法学限制有关。禽脑与哺乳动物大脑之间的解剖差异，以及关于禽脑疼痛处理特定部位的知识匮乏，可能意味着从头部表面记录的 EEG 对禽脑疼痛处理区域的神经活动变化不敏感。未来的研究应根据参与疼痛处理的哺乳动物脑区的禽脑同源物，检查替代电极放置部位。
