Date Published: February 22, 2019
Publisher: Public Library of Science
Author(s): Jessica E. Martin, Victoria Sandilands, Julian Sparrey, Laurence Baker, Laura M. Dixon, Dorothy E. F. McKeegan, Arda Yildirim.
There is a need for novel mechanical devices for dispatching poultry on farm following the introduction of EU Regulation (EC) no. 1099/2009 On the Protection of Animals at the Time of Killing. We examined three novel mechanical killing devices: Modified Armadillo, Modified Rabbit Zinger, a novel mechanical cervical dislocation device; and traditional manual cervical dislocation. The four killing methods were tested on 230 chickens across four batches. We measured behavioural, electroencephalogram and post-mortem outcomes in anesthetized laying hens and broilers at two life stages (juveniles and adults/slaughter age). Graeco Latin-Square designs systematically randomized killing treatment, bird type, age and kill order. All birds were lightly anaesthetized immediately prior to the killing treatment with inhalation of Sevoflurane. The novel mechanical cervical dislocation method had the highest kill success rate (single application attempt only, with no signs of recovery) of a mechanical method (96%). The Modified Armadillo was the least reliable with 49% kill success. Spectral analysis of electroencephalogram signals at 2 s intervals for successfully killed birds only revealed progressive decreases in median frequency alongside increases in total power. Later, total power decreased as the birds exhibited isoelectric electroencephalogram signal. Latencies to pre-defined spectral ranges associated with unconsciousness showed that birds subjected to manual and novel mechanical cervical dislocation achieved these states sooner than birds subjected to the modified Armadillo. Nevertheless all methods exhibited short latencies (<4 s). The Modified Rabbit Zinger had the shortest duration of reflex persistence for nictitating membrane, pupillary and rhythmic breathing post method application. Of the methods tested, the novel mechanical cervical dislocation device is the most promising mechanical method for killing poultry on-farm based on a range of behavioural, electroencephalogram and anatomical parameters. This device has the potential to fulfil the current need for a mechanical alternative to manual cervical dislocation.
Poultry need to be dispatched on-farm for multiple reasons (e.g. injury, sickness and for stock management), either on a group/large scale (e.g. whole-house or containerized gassing [1–2]) or as individuals (e.g. manual cervical dislocation or captive bolt [3–5]).The industry standard for killing individual chickens on-farm is cervical dislocation as it is perceived to be humane by users, and is easy to learn and perform . There are two types of cervical dislocation: manual and mechanical. Both are designed to separate the skull from the vertebral column (ideally C0–C1 vertebral dislocation) and sever the spinal cord and/or brainstem and the main blood vessels supplying the brain [7–8]. Mechanical cervical dislocation is differentiated from manual dislocation by the use of an aid or tool in order to complete the action (e.g. killing cone ) . Mechanical methods have had limited uptake within the poultry industry due to practical limitations (e.g. non-mobile killing cone). Optimally, cervical dislocation should have a concussive effect through brain stem trauma and cause death by cerebral ischemia [3,10]. Previous work on cervical dislocation (mechanical only) suggested that birds may be conscious for a significant period post-application [3,11]. Accordingly, current EU legislation, Regulation (EC) no. 1099/2009 On the Protection of Animals at the Time of Killing , restricts the use of manual cervical dislocation in terms of number of birds which can be dispatcher per person per day (to 70), as well as applying weight limits of individual birds killed for both manual (<3 kg) and mechanical (<5 kg) cervical dislocation methods. This creates a need to develop new mechanical devices to provide alternative methods to kill individual birds on farm which are humane and practical, as well as comply with legislation. Some new methods have been primarily developed to dispatch larger birds (e.g. CASH Poultry Killer, Turkey Euthanasia Device) [3,12–13]. However, none have been enthusiastically adopted by the poultry industry, especially for chickens (laying hens and broilers) who represent the greatest demand in terms of bird numbers. This work was performed under Home Office (UK) authority via Project and Personal Licenses and underwent review and approval by Scotland’s Rural College’s (SRUC) Animal Welfare and Ethical Review Body (AU AE 34–2012). This study provides a comprehensive assessment of the effects of three novel mechanical killing treatments (MARM, MZIN, and NMCD) and traditional manual cervical dislocation on laying hens and broilers at two ages. We captured iEEG signals and detailed behavioural/reflex responses, as well as post-mortem anatomical effects in the same individual birds, during application of on-farm dispatching methods. Manual cervical dislocation was the most reliable (100% success) followed by the NMCD (96%). This is the first assessment of true manual cervical dislocation  our findings suggest that welfare concerns raised previously may not be justified. However, since EU Regulation (1099/2009) limits MCD in birds weighing over 3 kg and the total number of birds to 70 birds per person per day, a reliable and humane mechanical alternative is required. Source: http://doi.org/10.1371/journal.pone.0212872