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Mechanical, electrical or gas stunning; slaughter methods and monitoring signs of unconsciousness or consciousness
Controlled atmospheric stunning (CAS)



Design of facilities for CAS of pigs

  • The pre-stun facilities in lairage, including gondolas and automated gates to move the pigs, and the stunning chambers, pit, in addition to the post-stun facilities, should be specifically designed:
    • for CAS stunning and for the size and weight of pigs
    • to avoid injury, overcrowding or unnecessary stress
    • to continuously measure and display the gas concentration at induction and at the point of maximum gas concentration
    • the time of exposure should also be displayed or indicated
    • so animals can be visually monitored during the induction phase for any behaviour indicating distress from adverseness to the inhaled gas (agitation and escaping behaviour)
    • so animals can be accessed if the conveyance system fails, taking into account personnel safety
    • so the adjacent work area is equipped with gas-measuring equipment that continuously measure and display the gas concentrations
    • to provide a visible and audible warning to staff, if the gases used in stunning exceed the maximum allowed in the surrounding work area
    • so the concentration of gases in the work area do not exceed those permitted under provincial and/or federal OSH requirements
    • it is recommended to use the gondola group system for pit type of gas stunning systems since pigs are generally calmer when stunned in groups than when moved in single file to the stunner

Animal welfare PCP for gas stunning for pigs

  • The licence holder's PCP should include the following preventive measures, procedures and information:
    • a protocol for animal handling to be carried out by competent employees during pre-stun to minimize stress
    • the gas concentrations and time of exposure are documented in the PCP and selected to minimize the stress of induction of anesthesia
    • gas mixtures and methods that used are those proven to be effective and humane
    • a protocol to monitor the behaviour of animals during the induction of unconsciousness so that corrective actions can be implemented for observable problems:
      • such as animals piling up or falling on top of each, vocalizing or attempting to escape
    • the measures to ensure that exposure time and gas concentration are sufficient to ensure animals do not regain consciousness before death by bleeding
    • corrective action procedures to ensure humane stunning occurs during line stoppages
    • corrective action procedures to ensure that there is well maintained back-up stunning equipment available at all times
    • the procedure including test equipment and frequency for testing the stunning equipment

CAS of poultry

  • The licence holder's written animal welfare PCP should include the following preventive measures, procedures and information:
    • monitoring, verification and corrective action procedures to ensure birds are effectively stunned and do not return to sensibility before bleeding
      • in the case of irreversible CAS stunning, the outcome is that the birds are dead upon exit from the container; however this should be verified through validation or documented evidence that this outcome is consistently met
    • every establishment using gas stunning should have a written protocol that is linked to or is part of the establishment food safety PCP to identify DOAs and how identified DOAs are removed:
      • the licence holder may choose to identify and remove DOAs either before or after the CAS step
      • the protocol may be based on an acceptable standard or practice that is derived from documented evidence (such as scientific articles or studies) or it may be the result of validation studies conducted in the establishment
    • the system (including the modules if using a system where birds are not removed) where birds are exposed to the gas and the equipment used to convey them through the system should be designed and maintained to avoid injury and unnecessary stress
    • the gas system should be designed so birds can be visually monitored during the induction phase, throughout the stunning phase and accessed if the conveyance system fails in accordance with the PCP corrective action procedures
    • The following principles apply to humane treatment of the birds for gas stunning:
      • the gas mixtures and methods used are proven to be effective and humane
      • animals should not pile, vocalize, stand or fall on top of each other during the stunning process
      • the behaviour of birds during the induction of insensibility should be monitored, evaluated, and recorded and corrective action procedures taken for deviations
      • there should be an emergency back-up plan in the event of gas stunning equipment or system failure
    • This emergency plan should be well designed to ensure the humane treatment of the birds at all times and the prevention of prolonged periods of time that the birds are without food or water
    • It should include the proper use of well-maintained back-up stunning equipment
    • The operational parameters of the equipment should have a protocol that includes:
      • maintenance of the stunning equipment
      • how the equipment is tested and the frequency of testing
      • methods used to determine the gas concentrations
      • exposure times for the species, the size(s) of birds processed
      • the gas mixtures and methods used are those proven to be effective and humane
    • the establishment should have a protocol in place to identify birds that are conscious upon exit from the gas stunning system, through an effective monitoring procedure, especially if the outcome is not irreversible gas stunning, and ensure the birds are immediately re-stunned or humanely killed

Low atmospheric pressure stunning (LAPS)

  • LAPS is a computer controlled patented system that uses slow decompression (vacuum) to remove O2 (progressive hypobaric hypoxia) to achieve unconsciousness in the birds within the crates that automatically enter chambers; therefore there is minimal handling of the birds and no shackling prior to stunning.
  • LAPS may provide the same animal welfare standards not less than the presently accepted methods available.
    • Possible discomfort associated with this method must be controlled through the rate of decompression and O2
    • Signs of effective stun include ataxia, loss of posture and wing flapping from tonic/clonic convulsions caused by the anoxia.

Decapitation of poultry as a deviation procedure for missed stuns in poultry

  • Decapitation of birds can be used to slaughter birds, as a back-up process for birds that have not been properly rendered insensible by another method of stunning, such as an electric stunner or CAS.
  • Decapitation is to be performed by trained personnel or effective automatic decapitation equipment, using well maintained equipment (sharp knives or decapitation equipment) as per the licence holder's animal welfare PCP
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