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Simple Summary During poultry production, some birds are killed humanely on farm, usually because they are ill or injured. Recent European Union (EU) legislation has restricted the number of birds that can be killed by manual neck dislocation to 70 birds per person per day. We examined whether this limit is meaningful by investigating the effects of repeated application of two methods of killing (neck dislocation and a percussive method, the CashPoultry Killer). Twelve male stockworkers each killed 100 birds (broilers, laying hens, or turkeys) at a fixed rate with each method. Both methods were highly successful, and reflex and behaviour measures confirmed they caused rapid loss of brain function. Importantly, there was no evidence of reduced performance with time/bird number up to 100 birds with either method. The Cash Poultry Killer caused a more rapid death, but it was prone to technical difficulties with repeated use. Neck dislocation has the important advantage that it can be performed immediately with no equipment, which may make it preferable in some situations. We present the first evidence that, at the killing rates tested, there was no evidence to justify the current EU number limit for performance of neck dislocation to kill poultry on farm. Abstract Council Regulation (EC) no. 1099/2009 on the protection of animals at the time of killing restricts the use of manual cervical dislocation in poultry on farms in the European Union (EU) to birds weighing up to 3 kg and 70 birds per person per day. However, few studies have examined whether repeated application of manual cervical dislocation has welfare implications and whether these are dependent on individual operator skill or susceptibility to fatigue. We investigated the effects of repeated application (100 birds at a fixed killing rate of 1 bird per 2 min) and multiple operators on two methods of killing of broilers, laying hens, and turkeys in commercial settings. We compared the efficacy and welfare impact of repeated application of cervical dislocation and a percussive killer (Cash Poultry Killer, CPK), using 12 male stockworkers on three farms (one farm per bird type). Both methods achieved over 96% kill success at the first attempt. The killing methods were equally effective for each bird type and there was no evidence of reduced performance with time and/or bird number. Both methods of killing caused a rapid loss of reflexes, indicating loss of brain function. There was more variation in reflex durations and post-mortem damage in birds killed by cervical dislocation than that found using CPK. High neck dislocation was associated with improved kill success and more rapid loss of reflexes. The CPK caused damage to multiple brain areas with little variation. Overall, the CPK was associated with faster abolition of reflexes, with fewer birds exhibiting them at all, suggestive of better welfare outcomes. However, technical difficulties with the CPK highlighted the advantages of cervical dislocation, which can be performed immediately with no equipment. At the killing rates tested, we did not find evidence to justify the current EU limit on the number of birds that one operator can kill on–farm by manual cervical dislocation.

Simple Summary Large numbers of poultry are killed on farm (usually because they are ill or injured) and we have a responsibility to ensure that the methods used have minimal welfare impact. The traditional method of manual cervical dislocation (i.e., “necking” by hand), has been subject to welfare concerns and has recently been restricted by law in Europe, in terms of the number of birds that can be killed with this method per day. Alternative methods need to be developed and these must be humane, practical and reliable in commercial settings. We evaluated the performance and reliability of a novel mechanical cervical dislocation device in comparison with the traditional manual method. We tested the performance of multiple users of each method in commercial laying hen and broiler farm settings. The novel mechanical method was outperformed by the traditional manual method, and there were some issues with training, dependent on the stockworkers’ technique and experience. The results show that while the novel method has the potential to improve welfare, it requires further refinement and training optimization in order to provide a viable alternative to manual cervical dislocation across the poultry industry. Abstract Urgent development of alternative on-farm killing methods for poultry is required following the number restrictions placed on the use of traditional manual cervical dislocation by European Legislation (EU 1099/2009). Alternatives must be proven to be humane and, crucially, practical in commercial settings with multiple users. We assessed the performance and reliability of a novel mechanical cervical dislocation device (NMCD) compared to the traditional manual cervical dislocation (MCD) method. NMCD was based on a novel device consisting of a thin supportive glove and two moveable metal finger inserts designed to aid the twisting motion of cervical dislocation. We employed a 2 × 2 factorial design, with a total of eight stockworkers from broiler and layer units (four per farm) each killing 70 birds per method. A successful kill performance was defined as immediate absence of rhythmic breathing and nictitating membrane reflex; a detectable gap in the vertebrae and only one kill attempt (i.e., one stretch and twist motion). The mean stockworker kill performance was significantly higher for MCD (98.4 ± 0.5%) compared to NMCD (81.6 ± 1.8%). However, the MCD technique normally used by the stockworkers (based previous in-house training received) affected the performance of NMCD and was confounded by unit type (broilers), with the majority of broiler stockworkers trained in a non-standard technique, making adaption to the NMCD more difficult. The consistency of trauma induced by the killing methods (based on several post-mortem parameters) was higher with NMCD demonstrated by “gold standard” trauma achieved in 30.2% of birds, compared to 11.4% for MCD (e.g., dislocation higher up the cervical region of the spine i.e., between vertebrae C0–C1, ≥1 carotid arteries severed), suggesting it has the potential to improve welfare at killing. However, the results also suggest that the NMCD method requires further refinement and training optimization in order for it to be acceptable as an alternative across poultry industry, irrespective of previous MCD technique and training.

1.Four mechanical poultry killing devices; modified Armadillo® (MARM), modified Rabbit ZingerTM (MZIN), modified pliers (MPLI) and a novel mechanical cervical dislocation gloved device (NMCD), were assessed for their killing potential in chicken the cadavers of euthanised, of four bird type and age combinations: layer/adult, layer/pullet, broiler/slaughter-age, broiler/chick.2.A 4x4x4 factorial design (batch x device x bird type + age) was employed. Ten bird cadavers per bird type and age were tested with each of the four mechanical devices (N = 160 birds). All cadavers were examined post-mortem to establish the anatomical damage caused by each device.3.Three of the mechanical methods: NMCD, MARM and MZIN demonstrated killing potential, as well as consistency in their anatomical effects, with device success rates of over 50% indicating that the devices performed optimally more than half of the time. NMCD had the highest killing potential, with 100% of birds sustaining the required physical trauma to have caused rapid death.4.The MPLI was inconsistent, and only performed optimally for 27.5% of birds, despite good killing potential when performing well. Severe crushing injury was seen in >50% of MPLI birds, suggesting that birds would die of asphyxia rather than cerebral ischemia, a major welfare concern. As a result the modified pliers are not recommended as a humane on-farm killing device for chickens.5.This experiment provides important data on the killing potential of untried novel percussive and mechanical cervical dislocation methods, informing future studies.

An alternative emergency method for killing poultry on-farm is required following European legislation changes (EU 1099/2009), which heavily restricts the use of manual cervical dislocation. This study investigated the kill efficacy of two mechanical methods that conform to the new legislation: (i) a novel mechanical cervical dislocation device; and (ii) a modified captive-bolt device (Rabbit Zinger™) and manual cervical dislocation (the control). Killing treatments were applied to broilers and layers at two stages of production (broilers: 2-3 and 5 weeks of age; layers: 12-13 and 58-62 weeks), with a total of 180 birds. Latency to abolition of cranial and behavioural reflexes, as well as post mortem analysis of the physiological damage produced, were used to estimate time to unconsciousness and assess kill efficacy. The novel mechanical cervical dislocation device was reliable and a practical method for killing poutry on-farm (100% kill success), with the majority of cranial reflexes showing no significant differences between interval mean durations across killing methods (eg nictitating membrane [mean = 0.7-3.3 s], and rhythmic breathing [mean = 0.0-0.3 s]), however for jaw tone and pupillary reflex, the modified Rabbit ZingerTM had significantly shorter interval mean durations compared to the control and mechanical cervical dislocation device (mean differences: jaw tone = ~8 s; pupillary = ~38 s). The novel mechanical cervical dislocation device resulted in consistent anatomical damage to the birds (eg high dislocation of the neck and severing of the spinal cord) compared to the manual method, despite both having 100% success rate, while the modified Rabbit ZingerTM was difficult to operate and resulted in varied anatomical damage. The novel mechanical cervical dislocation device showed promise as a replacement kill method on-farm for poultry.