Slaughter Poultry

The welfare of birds during slaughter is protected by law and must be integral to every processing plant's Standard Operating Procedure. Sick and injured birds must be treated or killed on-farm. Any birds arriving at the plant with signs of injury or illness must be culled, without delay, in a humane manner.

Lairage should be monitored and changes made according to prevailing weather conditions to ensure that birds are not subject to avoidable discomfort. Modules and crates MUST be handled with due care and consideration for the welfare of the birds. The birds MUST always be handled in a calm and quiet manner. Birds should only be suspended on the shackle line for the minimum amount of time possible. All equipment, including backups must be checked and tested daily and an inspection-maintenance log kept. Regular cleaning and servicing of equipment results in smoother operations and better animal welfare. Backup systems MUST be kept in the place of slaughter incase of an emergency or equipment failure.

The slaughter process begins with catching the birds. Rough and aggressive techniques result in the birds panicking and they may get injured. Loose housed birds should be caught under dim lighting to reduce the risk of panic and smothering. Small pens may be erected to confine the birds prior to catching. Once caught the birds must be handled with due care and consideration if injuries are to be avoided. The method of handling will depend on the species and size of bird. Further guidance on catching techniques is available in the HSA publication Technical Note No. 15 Poultry Catching and Handling.

All stunning methods should minimise the risk of causing pain, fear or distress to the birds. Stunning MUST render the birds immediately insensible to pain, or if the method is slow acting, it must induce insensibility in a manner that does not cause pain, excitement or distress. Poultry may be stunned by electronarcosis, percussive stunning (captive-bolt) or controlled atmosphere (gas) stunning.

This is achieved by passing a current through the bird that causes immediate loss of consciousness and sensibility to pain. The stunning current may be delivered through hand-held electrodes for small flocks or through an electrified waterbath where larger throughputs are required. Whatever the delivery method, the current must be of sufficient strength and duration to ensure that the birds are rendered immediately insensible and that they remain insensible until death from bleeding. Electrical stunning equipment MUST have a display that shows the current and voltage being applied. All electrodes should be regularly cleaned and maintained to prevent a build-up of resistance due to deposits. The stunning machines should be regularly tested with a load of known resistance to ensure that sufficient current is reaching the birds.

With handheld stunners, a suitable method of restraining the bird should be employed. The bird may be caught by applying firm pressure against both sides of the body, trapping the wings against the body. Holding the bird under the arm pits with one hand holding the legs and the other supporting the breast allows the bird to be presented for stunning in a calm and safe manner. Before using a hand held stunner, it is essential that the correct electrodes are attached. For fully feathered birds such as chickens, ducks and geese, an electrode with pointed edges allows penetration of the feathers around the head thus providing better contact. Electrical resistance may be further reduced by wetting the bird's head. For bald or partially feathered bird eg turkeys, button or flat electrodes will provide sufficient contact if applied correctly. The electrodes should be inspected for damage at the beginning and end of each working day and should be regularly cleaned with an abrasive material during use. Regular cleaning reduces build-up of material that may increase the resistance and therefore reduce effectiveness of the stunning system. The electrodes must be applied in the area between the ears and the eyes with firm pressure and the current switched on without delay. This position approximates the location of the brain thus it ensures that the current spans the brain.

When using electrical waterbath stunners, it is essential that the shackles fitted to the line are correct for the size of bird to be processed. They should provide a secure fit without undue pressure. The electrical resistance at the shackle may be reduced by spraying with salty water. The time the birds are kept suspended should be kept to minimum. Breast comforters can reduce wing flapping. Excessive wing flapping can result in injuries and pre-stun shocks. The entrance to the waterbath should be rapid, such that the birds are immediately immersed, with the bird immersed up to the base of the wings. All birds should be immersed such that each one's head is completely submerged (eg up to the base of the wings). The immersed electrode should span the entire length of the waterbath. Electrical waterbath should be supplied with sufficient current to allow all the birds immersed at one time to receive theoretically, the minimum recommended current per bird.

neck arched with head held vertically
no rhythmic breathing
rigidly extended legs
constant, rapid body tremors
absence of a third eyelid (nictitating membrane) reflex
wings held tightly against body

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Birds may be killed by exposure to appropriate anoxic gas mixtures for durations that ensure that they die before they are bled. The gas mixtures that are permissible are listed within legislation. CAS works by starving the brain of oxygen thereby resulting in death. The permitted gas mixtures are designed to induce loss of consciousness without undue distress. Birds can, in some systems, be placed in the gas chamber whilst they are still in their crates, thus reducing the amount of handling stress. Moreover, they must be dead by the time they are shackled, thus preventing the pain of shackles and the distress of inversion on the poultry line. Another advantage over electrical stunning is that the birds do not suffer pre-stun shocks and carcases have less broken bones and haemorrhging. In order to realise the advantages of CAS, the chamber should be designed in a manner that allows monitoring of the gases and the birds within. The chamber MUST have sensors that monitor the gas concentrations and activate audible and visible alarms when the gas mixtures change to levels that might compromise welfare. It should allow for the observation of birds in the chamber and allow for speedy removal of the anoxic gases and supply of air in case of emergencies. There should be ready access to all the birds in all the stages of the stun-kill. It is recommended that the birds remain within the gas for at least 2 minutes (3 minutes for ducks) and all birds MUST be dead before they are shackled and bled. Should the system fail, all birds that are in the chamber and still alive must be killed in a humane manner using an appropriate method. Birds leaving the chamber should be monitored for signs of an effective stun-kill and signs of recovery. The signs of an effective stun-kill include;

a relaxed and recumbent body
absence of the nictitating membrane (third eyelid) reflex
fully dilated pupils
absence of rhythmic breathing.

Methods suitable for small scale or emergency slaughter include percussive stunning and neck dislocation.

This may be achieved by a blow to the head using a captive-bolt instrument or a weighted stick (not recommended). Striking the head may result in the brain colliding into the skull, or stressing the brain to an extent that normal brain function fails. When correctly used, concussion stunning can humanely kill the birds. However, it is not suitable for routine commercial harvests when no special made equipment exist. Without proper equipment, it is difficult to deliver a correct blow using makeshift equipment. Purpose made concussion stunners deliver a sufficient blow to the head to cause loss of sensibility and may kill the birds. Signs of an effective stun/kill include:

absence of rhythmic breathing (check for abdominal movement in the vent area)
uncontrolled wing flapping
leg flexion and extension
absence of vocalisation

Dislocating the neck of the bird may cause rupturing of the spine and concussion. When done correctly, this results in the bird losing consciousness immediately and irrecoverably. However, it is difficult to achieve concussion consistently using neck dislocation therefore this method is not suitable for routine commercial harvest. It may however be appropriate for small numbers of birds or for emergency killing. A humane alternative is electrical stunning followed immediately by neck dislocation. Methods that crush the neck (e.g. pliers) do not cause concussion and are therefore unlikely to cause painless or immediate loss of consciousness. Their use is therefore NOT recommended. It is important that a technician applying neck dislocation is mentally prepared to carry through the whole procedure. Practice on dead birds may improve the confidence in application of this method. The various means of achieving neck dislocation are detailed in the HSA publication, Practical Slaughter of Poultry A Guide for Small Producers 2nd Edition (pages 17-20).

Humane Slaughter Association