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Summary: reducing the incidence of wing flapping in conscious birds on a shackle line and reducing the occurrence of pre-stun shocks


  • Construct a straight shackle line from the first shackling point to the waterbath.
  • Avoid constructing bends and inclines in a shackle line.
  • Minimise the length of a shackle line to: a) avoid a need to increase the line speed, in order to reduce the time that conscious birds are suspended; b) reduce the number of conscious birds requiring attention during a line breakdown.
  • Unload, retrieve escapees and shackle birds calmly, gently and quietly.
  • Shackle birds in correctly-fitting and appropriately-shaped shackles; if shackles are too tight they may cause pressure/pain which may provoke wing flapping.
  • Replace any damaged or heavily-scaled shackles.
  • Use appropriate line speeds to prevent swinging of birds.
  • Ensure the line moves smoothly without jolting/jerking.
  • Maintain a low light intensity, or use low-intensity blue lighting.
  • Avoid passing the shackle line through areas of sudden bright light.
  • Prevent temporary loss of visual contact between neighbouring birds.
  • Minimise ambient noise (including the rattling of shackles).
  • Prevent sudden and excessive movement of air (wind tunnel effect - draughts may disturb birds).
  • Ensure shackles and the earthed rubbing bar do not trap and pinch birds’ toes or interdigital webbing since this may be painful and cause flapping.
  • Use equipment that touches the birds’ breasts, eg a breast contact strip or a breast support conveyor. Ensure breast contact is constantly maintained from the start of shackling through to the stunner.
  • An entry ramp must be designed and positioned to allow a gentle but rapid flick of a bird’s head into the water. Entry ramps also keep wings above the waterline and assist in preventing pre-stun shocks.
  • Prevent any overflow of water from the entrance to the stunner; set up a drainage system at the exit of the waterbath.
  • If electrified water does overflow from the entrance, install a non-conductive overlay atop the entry ramp, to electrically isolate the entry ramp.
  • Ensure the water level in a waterbath is set according to flock size, to allow immediate submersion of the head of the smallest bird.
  • A shackle line that descends at the entrance to a waterbath is a traditional design that lowers birds’ heads into the water. These dipping lines are typically only suitable at fast line speeds (otherwise the slow entry into the water gives conscious birds an opportunity to resist immersion). Large birds like turkeys and geese may also be at greater risk of pre-stun shocks to their wings on slow-moving dipped shackle lines.
  • Ideally a shackle line should not descend at the entrance to a waterbath, when used in conjunction with an entry ramp.

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



Next: Operating an electrical waterbath

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