Institute for Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK.
Poult Sci. 2013 Apr;92(4):858-68. doi: 10.3382/ps.2012-02749.
In low atmospheric pressure stunning (LAPS), poultry are rendered unconscious before slaughter by gradually reducing oxygen tension in the atmosphere to achieve a progressive anoxia. The effects of LAPS are not instantaneous, so there are legitimate welfare concerns around the experience of birds before loss of consciousness. Using self-contained telemetry logging units, high-quality continuous electroencephalogram (EEG) and electrocardiogram (EKG) recordings were obtained from 28 broiler chickens during exposure to LAPS in a commercial poultry processing plant. Application of LAPS was associated with changes in the EEG pattern in the form of increases in total power, decreases in mean frequency, and in particular, increases in slow-wave (delta) activity, indicating a gradual loss of consciousness. Increased delta wave activity was seen within 10 s of LAPS onset and consistently thereafter, peaking at 30 s into LAPS at which point the EEG signal shared characteristics with that of birds in a surgical plane of anesthesia. During LAPS, heart rate consistently decreased, with more pronounced bradycardia and arrhythmia observed after 30 s. No heart rate increases were observed in the period when the birds were potentially conscious. After an initial quiescent period, brief body movements (presumed to be ataxia/loss of posture) were seen on average at 39 s into the LAPS process. Later (after 120 s on average), artifacts related to clonic (wing flapping) and tonic (muscle spasms) convulsions were observed in the EKG recordings. Based on EEG analysis and body movement responses, a conservative estimate of time to loss of consciousness is approximately 40 s. The lack of behavioral responses indicating aversion or escape and absence of heart rate elevation in the conscious period strongly suggest that birds do not find LAPS induction distressing. Collectively, the results suggest that LAPS is a humane approach that has the potential to improve the welfare of poultry at slaughter by gradually inducing unconsciousness without distress, eliminating live shackling and ensuring every bird is adequately stunned before exansguination.
在低气压致昏（LAPS）中，通过逐渐降低大气中的氧气张力来使家禽在屠宰前失去知觉，从而实现渐进性缺氧。LAPS 的效果不是即时的，因此在失去知觉之前，鸟类的体验存在合理的福利问题。使用独立的遥测记录单元，在商业家禽加工厂中对 28 只肉鸡在暴露于 LAPS 期间进行了高质量的连续脑电图（EEG）和心电图（EKG）记录。LAPS 的应用与 EEG 模式的变化有关，表现为总功率增加、平均频率降低，特别是慢波（delta）活动增加，表明意识逐渐丧失。在 LAPS 开始后 10 秒内就可以看到 delta 波活动增加，此后一直持续增加，在 LAPS 开始后 30 秒达到峰值，此时 EEG 信号与处于手术麻醉平面的鸟类的信号特征相似。在 LAPS 过程中，心率持续下降，在 30 秒后观察到更明显的心动过缓和心律失常。在鸟类可能有意识的这段时间内，没有观察到心率增加。在初始安静期之后，在 LAPS 过程中大约 39 秒时，观察到短暂的身体运动（推测为共济失调/姿势丧失）。之后（平均 120 秒后），在 EKG 记录中观察到与阵挛（翅膀拍打）和强直性（肌肉痉挛）抽搐相关的伪影。基于 EEG 分析和身体运动反应，估计失去意识的时间大约为 40 秒。在有意识期间缺乏表明厌恶或逃避的行为反应，以及心率升高的缺乏，强烈表明鸟类不会发现 LAPS 诱导令人痛苦。总的来说，这些结果表明 LAPS 是一种人道的方法，通过逐渐诱导无意识而不会产生痛苦，消除活体束缚，并确保每只鸟在放血前都被充分致昏，从而有可能改善屠宰时家禽的福利。
