Humane slaughter checklist

A successful electrical waterbath slaughtering system is dependent on the following:

• Correct set-up of all equipment.

• Regular inspection, testing, calibration and maintenance of all components in the slaughter system, eg regularly clean electrodes and shackles with acid and wire brushes and check that no current flows when birds are not immersed in the electrified water.

• Fully trained, competent and compassionate lairage staff and slaughterpersons.

• Minimising fear, stress, discomfort and pain of birds during handling and shackling.

• Shackles must be dripping wet before birds are hung into them; this should enhance conductivity during stunning and may reduce frictional forces during shackling.

• Shackling birds for as short-a-time as possible.

• Use a breast contact strip or support conveyor that maintains contact with each bird’s breast throughout the duration of time the birds are shackled and conscious.

• A shackle line must be straight whilst the birds are conscious.

• Shackled conscious birds should be sufficiently spaced apart to prevent physical contact whilst in the waterbath; this may limit the variation in the current amplitudes received in a constant voltage stunner.

• Encouraging as many birds as possible to adopt an ideal posture for entry to a waterbath. Good entries may be seen in birds that hold their neck extended towards the floor, their head down and their wings folded into the closed position against the body. To assist, shacklers may need to gently fold a bird’s wings into the closed position, whether the birds are against a breast contact strip or on a breast support conveyor. With closed wings, birds may be less likely to touch one another in the waterbath.

• Slaughtering birds in batches in which the individuals are as uniform as possible. This should allow more efficient and humane stunning in terms of reduced compression of some birds’ legs, better entries to the electrified water and more similar current amplitudes when using a constant voltage stunner.
  • Avoid shackling together birds that are different in size (including length, leg circumference), age or expected body fat and muscle content. For example, slaughter males and females separately.
  • Runts or very small birds must not be shackled for waterbath stunning because they may miss the electrified water and/or miss an automated mechanical neck cutter. They must be slaughtered using an alternative humane stunning method.

• Prevention of pre-stun electrical shocks.

• A waterbath should be of an adequate size (particularly width and depth) for the type of bird being slaughtered. Undersized, or even oversized, individuals must not be shackled for waterbath stunning if their size puts them at risk of ineffective stunning.

• Monitoring the position of birds in the electrified water to increase the likelihood that sufficient current will flow through the target organ(s), ie the brain (and heart in the case of intended stun-killing).
  • The water level in a waterbath must completely cover the entire head of each bird (including the cranium of the smallest bird suspended) and, if necessary (eg in Europe), the neck and up to the rostral edges of the wings (ie shoulders).

• The submerged electrode must span the entire length and width of a stunner and the earthed rubbing bar(s) electrode must span the entire length of a stunner.

• Continuous physical contact between the components of an electrical circuit, throughout the intended duration of current flow, ie from the electrode/water to the bird’s head, the bird’s legs to the shackle and occupied shackles to the earthed rubbing bar(s). This should allow for receipt of a consistent amplitude of current.

• The good condition of all components that enable current flow. Replace if worn or damaged, or if scale or carbon residues are present and if descaler and acid are ineffective at removing the scale or residues. (Scale and carbon residues can impede current flow, even though there is physical contact.) Keeping resistance as low as possible at all conduction points between the birds and the electrodes may avoid the need to use excessive voltages to reach the required current.

• Selection of equipment capable of delivering electrical parameters appropriate for animal welfare.
  • The latency to deliver the recommended current may vary with the available and applied voltage. Electrical waterbaths must be supplied with an appropriate input voltage, to ensure stipulated currents are reached and birds become unconscious immediately.
  • It is necessary to program a constant voltage stunner to deliver a minimum voltage that is capable of delivering the recommended current to 100% of birds. When under load, the ammeter on the stunner control panel must display a total current that equals, or exceeds, the number of birds simultaneously in the water multiplied by the minimum recommended current per bird. If birds are stunned in mixed-sex batches, abattoirs must use a voltage sufficient to ensure all sexes receive the minimum recommended current amplitude. Alternatively, if necessary and if practical, separately slaughter males and females (eg broiler chickens) in order to provide females with the necessary higher voltage and to limit any damage to the carcasses of males.
  • If, in future, a true constant current stunner becomes available, it is likely to be preferable to use that type of stunner because it should be able to control the delivery of a constant current to each individual bird. This should be irrespective of the number of birds in contact with the water, any differences in resistance attributable to species, breed, strain, sex and age of bird, as well as the electrical waveform, all of which are otherwise difficult to predict and control for.

• Choose electrical parameters that should ensure 100% of birds are immediately stunned and remain so until death occurs.
  • Apply a current that at least meets, or exceeds, the threshold amplitude recommended to induce generalised epileptiform activity followed by a quiescent EEG.
  • Sine AC may provide a more effective stun than other AC and pDC waveforms.

• Monitoring equipment to ensure it actually delivers electrical parameters as appropriate for the welfare of each type of bird. Use the waterbath control panel ammeter and remote stun monitors to check that current is applied for a sufficient duration, not exceeding the recommended maximum frequency or using less than the recommended minimum amplitude of current.

• Installation of slaughter systems in a layout that allows personnel to safely and easily assess and access birds at any point on a shackle line, from shackling to entry to a scald tank. If access is denied because personnel are obstructed by features of the system or other equipment, eg if fast line speeds or the height of a shackle line effectively puts the birds out of reach, then the system should be redesigned. Use equipment that enables operators to access birds quickly in emergencies.

• Construction of shackle lines in a layout that enables birds to be checked for effective stunning before their necks are cut.

• Recognition of an ineffective stun.

• Birds must not be passed through a waterbath until a slaughterperson or ANC is ready and waiting to cut the birds.

• Accurate, consistent severing of at least both common carotid arteries and both external jugular veins, as soon as possible and within 10 seconds of high frequency stunning and 15 seconds of ‘standard’ frequency (eg 50 Hz) stunning.
  • For all species, it is necessary to cut into the neck muscle, to sever the carotids.
  • A ventral neck cut is an effective means of reliably severing both carotid arteries and therefore for bleeding birds as much, and as quickly, as possible, thereby protecting their welfare and benefitting meat quality.
  • Sufficient time for a bird to bleed out (incomplete bleeding may lead to downgrading of breast fillets and red wing tips).

• Recognition of an ineffective neck cut. If an operator is unsure if the carotid arteries are cut, they must cut the bird again.

• Rehearsed contingency plans. For example, if power to a waterbath fails:
  • The shackle line must automatically stop to prevent conscious birds’ heads being immersed in non-electrified water.
  • Birds that have already received an electric current and are unconscious must receive a ventral neck cut immediately, to prevent recovery.
  • Birds that received an electric current and are showing signs of recovery must be re-stunned using a back-up method and then bled.

• Immediate availability of a sufficient number of humane back-up stunning devices.

• Clear standard operating procedures. For example, if there is any indication that restraint, stunning or killing equipment is not operating effectively, slaughter must cease until the system is checked and any faults are corrected. An electrician or electrical engineer must be on-site and on-call during slaughter, in order to respond quickly and effectively to equipment failures.

• All personnel taking remedial action and/or immediately informing an AWO and the veterinarian, of any sick, injured or ineffectively stunned or ineffectively cut birds.

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For more detailed information (including general maintenance of equipment, standard operating procedures, animal welfare policies and training, useful contacts and publications and a glossary of electrical waterbath terminology) suitable for Animal Welfare Officers, Official Veterinarians and abattoir management, please view the HSA Guidance Notes No.7 on ‘Electrical Waterbath Stunning of Poultry’, which can be downloaded free-of-charge and is also available in French (également disponible en français).