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The shackle line

The shackles should be well-maintained and wetted immediately prior to shackling a bird.


Shackles shall be wet before live birds are shackled and exposed to the current. Birds shall be hung by both legs.”  European Council (EC) Regulation No. 1099/2009



The size and shape of the metal shackles shall be appropriate to the size of the legs of poultry to be slaughtered so that electrical contact can be secured without causing pain.  EC Regulation 1099/2009*

*abattoirs with relevant equipment that was in use prior to 1 January 2013 have until 8 December 2019 to comply with Article 14(1) and Annex II of Regulation 1099/2009, including the requirement above. (Abattoirs, layouts or equipment constructed after 1 January 2013 must apply the requirements immediately.)


Shackles have the potential to compress the tissues of the shank, including the innervated periosteum (connective tissue containing nerves and surrounding the bones) and the tarsometatarsal bone, which is potentially painful for a conscious animal and may cause damage (Figure 2). Therefore abattoirs must use shackles that have the correct size (gauge) slot for the birds’ legs. Larger, heavier birds are likely to have legs with a larger diameter/circumference (eg male broiler chickens). Shackles with tapering slots are preferable to parallel-slot shackles. If an abattoir processes different species, types, sexes or sizes of bird, then shackles with multiple slots of varying tapering gauges should be installed, to allow birds to be shackled according to their size, thereby limiting (to a degree) leg compression.

Shacklers must not use excessive force when loading a bird into a shackle, because this may cause further compression of the legs. It can be difficult to determine the sex of some types of birds (eg broiler chickens), especially when shackling them at fast line speeds. In such circumstances, and if abattoirs use multi-slot/gauge shackles, it may be appropriate to slaughter males and females separately so shacklers can be instructed, in advance, which shackle slot to use. For example, males can be shackled in the larger slot and females in the smaller slot. However, shacklers should be encouraged to use their initiative also and, as appropriate, shackle a large female or a small male bird in a larger or smaller slot, respectively. Although a shackle should not cause compression injuries or pain, the fit should be sufficiently firm to prevent excessive movement or escape and to allow for good electrical contact for stunning.

Shackling imposes a greater load on birds’ legs as bird weight increases. For this reason, heavy birds (eg exceeding 15 kg live weight) should not be shackled for waterbath stunning but should instead be slaughtered using an alternative humane restraint, stunning and killing method (eg restraint cone and captive-bolt followed by exsanguination).


Figure 2. Shackling damage (bruising indicated by arrows) to the shanks of chickens. Bruises are a sign of poor animal welfare.




The duration for which each bird may be shackled

Involuntary inversion appears to cause poultry stress. It is not their default stance and birds do not have diaphragms, so inversion may feel uncomfortable if the viscera compress the heart and lungs. For this reason, and because shackling conscious birds may be painful, it is necessary to minimise the duration that birds are inverted and restrained on a shackle line. Whilst it may sometimes be necessary to allow a short time for birds to reduce their activity and settle down on a shackle line (so they enter the waterbath calmly and smoothly, reducing the risk of pre-stun shocks), the suspension time should always be as short as possible. For example, EFSA (2004) and the OIE (2014) recommended a maximum shackling time of one minute but EFSA (2004) reported 12 or 20 seconds may be sufficient time for chickens and turkeys respectively, to settle on a shackle line.


Maximum durations that conscious birds can remain suspended in shackles before waterbath stunning, according to EC Regulation 1099/2009*:

  • Two minutes for ducks, geese and turkeys
  • One minute for all other species of poultry

*abattoirs with relevant equipment that was in use prior to 1 January 2013 have until 8 December 2019 to comply with Article 14(1) and Annex II of Regulation 1099/2009, including the requirement above. (Abattoirs, layouts or equipment constructed after 1 January 2013 must apply the requirements immediately.)


Shackle line design 

Shackle lines must be designed to minimise disturbance of suspended birds. Ideally, all sections of a shackle line conveying conscious birds must be straight (ie no corners) and without inclines, whether ascents or descents. A shackled bird must be kept clear of any obstructions that might cause panic, struggling, pain or injury, including when a bird’s neck and wings are fully outstretched and if it flaps. Obstructions may include neighbouring birds; if a flapping bird hits its neighbour(s) with its wings, the neighbour(s) may also be disturbed and begin flapping. Shackle lines must be constructed and maintained so they do not jolt birds because this is likely to stimulate flapping. Shackle line speeds must be of a pace that does not cause the birds to struggle. Fast line speeds may cause birds to notice inclines, to swing round any corners (if corners still exist on some shackle lines) and to lose contact with the breast contact strip, initiating wing flapping. The line speed must also be appropriate for each operator to safely, comfortably, gently and effectively shackle and thereafter, whenever necessary, tend to a bird on the shackle line (eg back-up stun/kill it or remove it from the shackle), without undue haste.


At a given line speed, there must be a sufficient number of shacklers so that each has sufficient time to identify, separate and kill (or immediately pass to another appropriate person to kill) any birds that are unfit to undergo the routine slaughter method. All operators responsible for poultry welfare must always be able to visually monitor shackled birds, but it is better if a shackle line is not in such close proximity to operators (or to thoroughfares for other personnel) that their routine working movements disturb shackled birds.

The controls of all processing equipment should be immediately accessible, should the need arise to stop the shackle line in an emergency. For example, multiple emergency-stop buttons or a pull-cord spanning the entire length of a shackle line (from the shackling station to the scald-tank) will allow personnel to immediately stop the line and raise the alarm. Personnel should be encouraged to activate these emergency-stop systems if they foresee or witness an emergency (eg a live bird entering a scald-tank or plucker). Correspondingly, the whole length of a shackle line from the hang-on point furthest from the waterbath, to the point of entry into the scald-tank must be readily accessible to abattoir personnel, should any bird need immediate attention.

If a line stops and conscious birds are likely to be suspended for longer than the recommended or legal maximum duration, they should be immediately stunned and killed, in their shackles, using a humane back-up method. It is preferred, for bird welfare, to stun and kill birds in their shackles, to avoid the additional handling (which may compound any stress) and the potential discomfort (eg recompression of the legs) if birds are either unshackled and then killed using a back-up method, or if they are unshackled, recrated and later reshackled (on potentially damaged legs) for waterbath stunning, once the system restarts.





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