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Mechanical, electrical or gas stunning; slaughter methods and monitoring signs of unconsciousness or consciousness
Electrical stunning

Electrical stunning methods for mammalian food animals

  • Electrical stunning includes hand-held and automated electrical stunning equipment.
  • Correct use of this equipment includes:
    • the right equipment is used for the right species at all times
    • the current (amperage and voltage) is adequate for the species slaughtered to avoid electroimmobilization
    • employees who conduct the stunning require adequate training for the specific equipment used
    • animals are well restrained and stay calm
    • for head-only stunning, the outcome is a reversible stun
    • the electrodes must always be placed to span the brain for the current to flow properly through the brain for all food animals
      • therefore, the electrode(s) are not positioned on the animal's neck or muzzle, for example for rabbits:
        • when electrical head-only stunning equipment for rabbits is used to make contact with the muzzle of the rabbit and not span the brain, this will cause electroimmobilization only and not an effective stun
      • for head only electric stunning, the stun-to-stick interval should not exceed 15 seconds for most species
    • for head-to-body stunning, the outcome is generally an irreversible outcome, when done properly
    • incidents of preshock or electroimmobilization are to be monitored to prevent avoidable suffering:
      • hot wanding occurs if an animal receives a cardiac shock before they receive a head stun
      • preshocked animals will generally vocalize because of the pain (except for sheep)
  • The licence holder's written PCP should include the following preventive measures, procedures and information:
    • the stunning equipment is clearly defined which type of stunning it is meant to provide , including reversible or irreversible stunning outcome
    • the protocol requiring that it is used properly as per the manufacturer's specifications to result in an effective stun
      • the equipment is positioned correctly to span the brain for the current to flow through the brain
    • there is a written protocol for the routine maintenance of the equipment
    • the procedure including test equipment and frequency for testing the stunning equipment
      • it is never tested on a live animal
      • frequency should include at a minimum at the startup of production, production shift changes, before each new lot of animals or employee shift changes
    • the recommended equipment settings for each size of animal that is stunned including specification of:
      • the voltage
      • amperage
      • the current frequency
      • type of current (AC vs DC or both)
      • type of wave form (sinus, square)
      • the time of stun
    • In cases where the manufacturer's recommendations are not used, there should be documented evidence or a validation study in the establishment to support the alternative approach
    • the voltage and amperage are monitored, easy to see and are recorded on an ongoing basis throughout the shift
    • the amperage is the more important parameter to assess effective stunning
    • the length of time of the current is applied on the animal is measured and recorded
    • a backup and well maintained stunning equipment should be quickly available as a deviation procedure

Electrical stunning systems for poultry

Electrical multiple bird stunning systems for poultry

  • Waterbath and plate stunners are available as single phase or multiphase systems:
    • either only one electrical phase of one waveform and current amplitude is used, or two phases of differing waveforms and/or current amplitudes are used consecutively:
      • For example, for a two plate, two phase system:
        • one phase delivers an AC (lower frequency alternate current phase, with sinusoidal waveform) current and the other delivers a DC pulsed current (higher frequency, direct pulsating current phase)
        • each phase section (AC and DC) should be equipped with meters to measure the amount of current, as well as voltage, being supplied to that section of the stunner to assess the effective functioning of the equipment
        • the calculations of the amount of current being provided to stun each bird is not the sum of the amount delivered to each phase since each section is a separate stunning phase of the entire system and the amount delivered to each bird depends on the number of birds in each stunning phase at one time
        • each phase section (AC and DC) should be supplied with sufficient current to render the bird insensible, otherwise there is a risk of ineffective stunning or electroimmobilization
        • the ground bar should come in contact with all shackles over the AC and DC phase sections
      • For example for a single phase waterbath system:
        • the height of the waterbath stunner water level and the level of brine in the waterbath stunner are adjusted throughout the day as needed to ensure even the smallest birds are submerged up to the base of their wings, or the birds' shoulders in the electrified water
        • For systems requiring increased salinity, salt can be added to the waterbath solution before the stunning starts and an effective salt concentration of the brine is maintained throughout the day to facilitate the flow of an effective electric current through the birds
        • Both AC or DC currents are used in single phase water bath systems with either sinusoidal or square waveforms
        • lower frequencies at higher amperages and voltages produce more effective and longer stunning times in the birds
      • For example for a single phase plate (grid) stunner:
        • For the electrical current to flow properly to the brain, the plate should make contact with the eye of the bird (side of the head)
        • When using high enough voltages, they can be effective for head-only stunning
        • most electric plate stunners are designed to have a brine solution that just covers the electric plate (wet plate)
  • Effective stunning is highly dependent on the voltage and especially the current amperage used:
    • poultry are electrically stunned using sufficiently high current, voltage and length of application, the stun could become irreversible and result in the bird's death
    • when using lower voltages for electric wet plate stunners, there can be a higher inherent risk of electroimmobilization or ineffective stunning
    • in general, the higher the frequency and the lower the voltage and current amperage, the more likely the bird will return to sensibility rapidly and the higher the risk for birds that could be electroimmobilized
    • theoretically, the current flowing through each bird is dependent on the total amperage of current, the number of birds and the amount of resistance in each bird
    • in practice, divide the total current flow registered on the ammeters by the number of birds in the bath to get an approximate idea of current amperage per bird
      • Note that even with low frequency, high current systems, the bird may recover to some degree if the current is not delivered properly to the individual bird.
        • Some reasons for this include higher resistance from an individual bird or the bird's incorrect positioning when presented to the source of electricity.
      • Electroimmobilization may occur if the current bypasses the brain in the multiple bird electrical waterbath or plate systems.
        • For example, this can occur if a bird swan necks and another body part makes contact with the electrified waterbath first for electrical waterbath stunners and therefore the brain is bypassed with no resulting epileptic seizure.
  • For all multiple bird systems, birds should only be suspended on the shackle line for a minimum amount of time, not more than 2 minutes for ducks, geese and turkeys and not more than 1 minute for other poultry prior to stunning because:
    • they have no diaphragms and there is increased cardiac pressure and bird death when in a prolonged inverted position
    • furthermore, there is the risk of pain and injury from the shackle from compression on the metatarsus, especially if it is not the correct size slot for the size of bird
      • shackles with moveable, tapering slots generally work better than parallel slots
      • if the shackles are too large there will be poor contact and insufficient current flow
      • if the shackles are too small it will be painful and induce flapping which interferes with stunning
      • wetting shackles can improve conductivity
  • The output of the electrical equipment (volts or amps) should be tested under load, using equipment which can simulate the resistance of a shackled bird or a bird's head depending on the placement of the electrodes
  • the waterbath should be sufficiently large (width, length and depth) to accommodate the wing span and body mass for the type of bird(s) being slaughtered and to avoid birds heads or other parts being trapped outside of the waterbath sides
  • all equipment should be cleaned, maintained, adjusted and tested to ensure it is operating properly with good current flow before the beginning of each day's operations
  • the water bath (live) electrode needs to be kept clean and must run the entire length of the waterbath to facilitate current flow
  • the ground (shackle) electrode needs to be regularly cleaned and have constant contact with the shackles since intermittent contact results in a less effective, intermittent stun

Animal welfare PCP for electrical multiple bird stunning of poultry

The licence holder's PCP should include the following preventive measures, procedures and information:

  • protocol for the maintenance of the stunning equipment
  • methods used to determine the electrical settings for each lot and type of birds processed, including a means to validate effective stunning parameters
  • the recommended equipment settings for each size of bird that is stunned including specification of:
    • the frequency of current (AC/DC) and which one is used for which step
    • the time of stun (taking into account the line speed and length of the stunner)
    • number of birds stunned at the same time and for each step in a two-phase system
    • the protocol for the maintenance of the equipment for salinity flow
    • the protocol for level of salinity used and its adjustment including:
      • manufacturers recommended procedures to enhance the salinity of water to improve electrical conductivity, as required
    • correct flow of the brine to avoid preshock from the brine flowing out the entrance to the bath
    • maintenance and cleaning protocol of shackles for electric contact to prevent poor electrical conductivity
    • the protocol for staff for stopping the line in the stunning and bleeding areas in the event of a problem or communicating problems so that corrective action procedures can be immediately taken
    • the system used should have meters or the proper software if computerized that display or record the amperage (ammeter) and/or volts (voltmeter), frequency and duration of the stun
    • meters (voltmeters and ammeters) are best installed where clearly visible to staff operating the electrical water bath or plate stunning systems and to any person who monitors, verifies, inspects or audits the system
  • the procedure including test equipment and frequency for testing the stunning equipment
    • it is never tested on a live animal
    • frequency should include at a minimum at the startup of production, production shift, before each new lot of birds or employee shift changes

Electrical stunning of poultry and ratites head-only stunning, hand-held or automated equipment (poultry)

  • Electrical head-only stunning includes hand-held and automated electrical stunning equipment.
  • The electrodes, whether hand-held or automated (multiple bird systems) must still span the brain to produce an effective stun
  • Equipment that is designed for a single point contact with the head or neck (for example, an electric knife) may not produce an effective stun; there is the risk that it will only immobilize (paralyze) the bird without inducing unconsciousness.
  • For ratites (emus, rheas and ostriches), if hooded, this will require increased amperage for an effective stun
  • The licence holder's PCP should include the following preventive measures, procedures and information:
    • the recommended equipment settings for each size of bird that is stunned including specification of:
      • the voltage
      • amperage
      • the current frequency
      • the time of stun
      • a means/protocol to validate effective stunning parameters
      • the electrical stunning equipment is maintained and cleaned, as stated in the licence holder's written PCP and the manufacturer's specifications
      • in cases where the manufacturer's recommendations are not used, documentation to explain the rationale for the alternate approach should be developed and maintained
      • the voltage and amperage are monitored and recorded throughout the shift
      • the length of time of the current is applied is measured
    • safeguards that the equipment does not deliver any shock before stunning occurs
      • requirements that the electrodes are always positioned to span the brain and never on the bird's neck or beak
    • requirements that the stun-to-stick interval should not exceed 15 seconds
    • requirements for a backup stunning equipment to be available and properly functional
    • the procedure including test equipment and frequency for testing the stunning equipment
      • it is never tested on a live animal
      • frequency should include at a minimum at the startup of production, production shift, before each new lot of birds or employee shift changes

Undersized birds

  • undersized birds should not be hung, unless they can be effectively stunned by the water bath with the proper adjustments of the equipment
  • these undersized birds or runts should be humanely killed by an appropriate method if they cannot be effectively stunned

Pre-stun shocks

  • Pre-stun shocks should be monitored and prevented since it is painful for the birds and the licence holder should take the necessary steps to prevent it, including the determination of the root cause.
  • Pre-stun shock occurs when any part of a bird receives an electric shock before it enters the waterbath or in other cases, before it is effectively stunned.
  • Examples of these other cases include, the brine level being too low or the bird being too small to contact the water properly.
  • A ramp at the entry to the waterbath or plate system with water should be sloped to swing the birds into the waterbath
  • The ramp should also be either insulated or isolated by inserting a layer of non-conducting material (in the form of sheets or rods) between the ramp and the birds to avoid the birds making direct contact with any electrified water on the ramp
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