Retter Karina, Esser Karl-Heinz, Lüpke Matthias, Hellmann John, Steinhagen Dieter, Jung-Schroers Verena
Fish Disease Research Unit, Institute for Parasitology, University of Veterinary Medicine, Bünteweg 17, D-30559, Hannover, Germany.
Institute of Zoology, University of Veterinary Medicine, Bünteweg 17, D-30559, Hannover, Germany.
BMC Vet Res. 2018 Jun 27;14(1):205. doi: 10.1186/s12917-018-1530-0.
Common carp Cyprinus carpio is an important food fish in Central Europe, which in some regions is consumed as part of local tradition. The majority of carp are sold by small retailers and not processed in commercial processing plants. The overall objective of this study was to monitor how animal welfare is safeguarded during the stunning and slaughtering of carp for retail sale. For this, the stunning and slaughtering process was monitored on 12 carp farms. Four welfare-related parameters were assessed: (i) stunning success, (ii) injuries related to the applied stunning method, (iii) time between stunning and slaughter, and (iv) visible responses of carp during slaughtering. In addition, indicators of physiological stress were measured. In order to analyse whether the absence of behavioural indicators of consciousness after electrical stunning was correlated with unconsciousness a complementary laboratory study was performed. Here, carp were exposed to electrical current densities between 0.09 and 0.41 A/dm. The presence of behavioural responses and visually-evoked responses (VER) in the electro-encephalogram in response to light flashes as indicators for an absence of consciousness was recorded.
The carp farms applied manual percussive (18%) or electrical (23%) stunning methods, while the majority of farms used a combination of electrical stunning immediately followed by manual percussive stunning (59%). In the latter condition, 92.6% of stunned carp displayed no behavioural indicators of consciousness and significantly fewer injuries related to mishits compared to sole percussive stunning. In the laboratory study, behavioural indicators of consciousness recovered in carp between 1 and 9 min following removal of the electrical current. However, VER could be recorded already at 30 ± 8 s post stunning. This indicates a fast recovery of carp from electrical stunning when exposed to current densities in the range of those generated by commercially available stunning instruments for fish.
Under field conditions, percussion (applied manually) and electrical stunning might be poor inducers of unconsciousness before slaughter, while a combination was most effective. In order to undertake improvements in electrical stunning, further investigations into the current density, required for inducing prolonged insensibility in carp during electrical stunning, are needed.
鲤鱼是中欧一种重要的食用鱼，在一些地区是当地传统饮食的一部分。大多数鲤鱼由小零售商销售，而非在商业加工厂进行加工。本研究的总体目标是监测零售用鲤鱼在致昏和屠宰过程中动物福利是如何得到保障的。为此，在12个鲤鱼养殖场对致昏和屠宰过程进行了监测。评估了四个与福利相关的参数：（i）致昏成功率，（ii）与所用致昏方法相关的损伤，（iii）致昏和屠宰之间的时间，以及（iv）鲤鱼在屠宰过程中的可见反应。此外，还测量了生理应激指标。为了分析电击致昏后意识行为指标的缺失是否与无意识状态相关，进行了一项补充实验室研究。在此研究中，将鲤鱼暴露于0.09至0.41 A/dm²的电流密度下。记录了脑电图中对光闪烁的行为反应和视觉诱发电位（VER）的存在情况，以此作为无意识状态的指标。
鲤鱼养殖场采用手动敲击致昏法（18%）或电击致昏法（23%），而大多数养殖场采用电击致昏后紧接着手动敲击致昏的组合方法（59%）。在后一种情况下，92.6%的致昏鲤鱼未表现出意识行为指标，与单纯敲击致昏相比，因误击导致的损伤明显更少。在实验室研究中，电流移除后1至9分钟内鲤鱼的意识行为指标恢复。然而，致昏后30±8秒即可记录到VER。这表明当鲤鱼暴露于市售鱼类致昏仪器产生的电流密度范围内时，它们能从电击致昏中快速恢复。
在实地条件下，（手动）敲击致昏和电击致昏在屠宰前可能难以有效诱导无意识状态，而两者结合最为有效。为了改进电击致昏方法，需要进一步研究在电击致昏过程中使鲤鱼长时间失去知觉所需的电流密度。
