背景:彩虹鳟鱼,Oncorhynchusmykiss,是欧洲淡水水产养殖的重要鱼类。这个工业部门由位于农村地区的小型家族企业主导。这些小企业生产的大部分虹鳟鱼直接销售并按需杀死,而不是在商业加工厂加工。欧盟和国家法规规定,鱼类在杀戮和屠宰前应被击昏。这项研究的总体目标是监测如何将惊人的干预措施整合到德国常规鳟鱼水产养殖的生产链中,以在惊人和杀戮期间保护动物福利。为此,在德国联邦各州的18个虹鳟鱼养殖场监测了令人惊叹的屠宰过程。在农场研究期间,(I)惊人的成功,(ii)与击晕程序有关的伤害,(iii)击昏和杀戮之间的持续时间,(iv)屠宰时的可见反应被评估为福利指标。此外,血液和生化血液参数被测量为生理应激的指标。由于惊人的干预措施会导致鱼类意识丧失,在实验室研究中,检查是否没有脑干/行为反应,眼运动(OM)或眼球滚动反射(前庭眼反射,VOR)与不敏感阶段相关。
结果:大多数虹鳟鱼养殖场采用了手动敲击(38%)或电击(48%),而在14%的农场,鱼被电击惊呆了,紧接着是手动敲击。在撞击令人惊叹之后,约92.3%的虹鳟鱼没有显示OM或VOR作为脑干/行为意识指标。这个百分比在使用惊人电的农场中有所不同。在大多数农场,根据脑干/行为指标的观察,95%至100%的鱼失去知觉,在虹鳟鱼在电流密度低于0.1Adm2或仅几秒钟的情况下被惊呆的农场中,惊人的干预效果较差。实验室研究证实,脑干/行为指标的缺乏与大脑对光刺激的视觉诱发反应(VER)的缺乏相关,作为神经元的不敏感性指标。因此,脑干/行为体征可用于解释虹鳟鱼的不敏感阶段。通过将部分大小的虹鳟鱼暴露于大于0.1Adm2的电流密度可以安全地诱发不敏感阶段。这不受电场方向的影响。
结论:在常规水产养殖中,虹鳟鱼可以通过手动打击乐或电动击晕有效击晕。意识可以通过没有手术运动或眼球滚动反射来监测,与神经反应(如VER)几乎同时丢失。为了在常规生产过程中惊呆和杀死虹鳟鱼期间保护动物福利,令人惊叹的过程需要仔细注意,操作人员需要接受使用令人惊叹设备和识别意识指标的培训。
BACKGROUND: Rainbow trout, Oncorhynchus mykiss, is an important fish in European freshwater aquaculture. This industry sector is dominated by small family-owned enterprises located in rural areas. A large percentage of rainbow trout produced by these small enterprises is marketed directly and killed on demand and not processed in commercial processing plants. EU and national regulations stipulate that fish shall be stunned prior to killing and slaughter. The overall objective of this
study was to monitor how stunning interventions were integrated into the production chains of German conventional trout aquaculture in order to safeguard animal welfare during stunning and killing. For this, the stunning and slaughtering processes were monitored on 18 rainbow trout farms in various German federal states. During the on-farm research, (i) the stunning success, (ii) injuries related to the stunning procedure, (iii) duration between stunning and killing, and (iv) visible responses at the time of slaughtering were assessed as welfare indicators. In addition, haematological and biochemical blood parameters were measured as indicators for physiological stress. Due to the fact that stunning interventions should induce a loss of consciousness in fish, in a laboratory
study, it was examined whether the absence of the brainstem/ behavioural responses, opercular movements (OM) or eye-rolling reflex (vestibulo-ocular reflex, VOR) was correlated with the stage of insensibility.
RESULTS: The majority of rainbow trout farms applied manual percussion (38%) or electrical stunning (48%), while on 14% of the farms, the fish were stunned by electrical stunning which was immediately followed by manual percussion. After percussive stunning, about 92.3% of the rainbow trout displayed no OM or VOR as brainstem/ behavioural indicators of consciousness. This percentage varied on farms which applied electrical stunning. While on the majority of farms, 95 to 100% of the fish were unconscious according to the observation of brainstem/ behavioural indicators, the stunning intervention was less effective on farms where rainbow trout were stunned at current densities below 0.1 A dm2 or for a few seconds only. The laboratory
study confirmed that the absence of brainstem/ behavioural indicators correlated with the absence of visually evoked responses (VER) of the brain to light stimuli as a neuronal indicator of insensibility. Therefore, the brainstem/ behavioural signs can be used to interpret the stage of insensibility in rainbow trout. A stage of insensibility could safely be induced by exposing portion-sized rainbow trout to an electric current density above 0.1 A dm2. This was not influenced by the orientation of the electric field.
CONCLUSIONS: In conventional aquaculture, rainbow trout can effectively be stunned by manual percussion or electrical stunning. Consciousness can be monitored by the absence of opercular movements or the eye-rolling reflex, which are lost approximately at the same time as neurological responses like VER. For safeguarding animal welfare during stunning and killing of rainbow trout in conventional production processes, the stunning process requires careful attention and the operating personnel need to be trained in using the stunning devices and recognising indicators of consciousness.