Summary - optimising current flow

Critical control points of electrical contact in a waterbath system:

• Earthed rubbing bar interface with shackle
• Shackle interface with a bird’s legs
• Bird head interface with water/electrode

Maintaining good quality electrical contacts and controlling resistance in a waterbath system:

• Install the earthed rubbing bar so it is pushing against all occupied shackles.
• Use a pair of earthed rubbing bars to secure and maintain constant contact with the shackles as birds enter, and whilst they are in, the electrified water.
• Ensure shackles are free from dirt, straw, feathers, severed feet and scale.
• Pre-wet empty shackles with a saline water spray immediately before the start of the shackling station.
• Ensure a firm fit between each leg and the shackle. Regularly monitor leg position in shackles to ensure it is optimum. If a significant proportion of birds is improperly shackled (eg have only one leg shackled), the gauge of the shackle slot may be inappropriate or the line speed may be too fast for the shacklers to work effectively, in which case the line speed should be reduced.
• If a fine saline solution is briefly sprayed onto the interface between the birds’ legs and the shackles immediately before the birds enter the electrified water, make sure the spray is targeted only at the interface between each bird’s legs and its shackle and that the spray is not soaking the birds’ bodies and plumage.
• Keep the birds’ bodies as clean and dry as possible, to enable current to flow through the brain and body interior as much as possible.
• Space birds far enough apart on the shackle line to prevent bodily contact, including if the wings flap or are held open. This may reduce bird disturbance, carcass damage and prevent the formation of lateral current pathways between birds during application of electricity.
• Ensure each bird’s whole head is immediately and completely submerged in the electrified water (and preferably touching the electrode) and that it remains so until the bird is withdrawn from the waterbath for bleeding.
• As the stunned birds exit the stunner, the shackle line should lift their entire bodies (including heads) clear of the end panel, to prevent contact. Although repeat application of current at the waterbath exit may not necessarily pose a welfare problem in unconscious birds, any current ‘spikes’ may damage the carcass.

Please refer to the HSA Guidance Notes No.7 on ‘Electrical Waterbath Stunning of Poultry’ if additional detail is required.

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