Actions that may minimise the risk of birds experiencing pre-stun shocks

To prevent pre-stun shocks, current flow to/through a bird must only be possible when the shackle is in contact with the earthed rubbing bar and, simultaneously, the bird’s head is in full contact with the electrified water in the waterbath.

Anecdotally, some birds that do not flap may fold their wings into the closed position (Figure 5a,b) and hold them against the sides of their body, naturally keeping the wings away from the electrified water and also avoiding contact with neighbouring birds. Such a bird may also hold its neck and head down in a vertical line, which may allow the head to enter the water smoothly. Personnel should strive to ensure handling and shackling is of the highest quality because it may encourage this behaviour in birds.

A steeply-inclined, smooth ramp ascending over the entrance to the waterbath (Figure 6) may reduce the number of birds experiencing pre-stun shocks. An entry ramp should begin below the level of the birds’ wings, to prevent wings from becoming caught on the edge of the ramp. A ramp should extend over the water a short distance and must briefly hold birds back at the top of the ramp (Figure 5a,b), so they gently, but rapidly, swing off the edge and their heads swing straight into the water in one smooth motion. The height and angle of a ramp must be adjustable so it can suit the shackle line and the size of bird being processed.

Care must be taken to ensure birds do not receive pre-stun shocks from the entry ramp itself, by electrically isolating the ramp from the rest of the waterbath. This can be achieved by ensuring there is no physical contact between the ramp and the waterbath and by ensuring the ramp does not have a flow of [electrically ‘live’] water running onto it from the waterbath.

Examples of different types of entry ramps can be found in the HSA Guidance Notes No.7 on 'Electrical Waterbath Stunning of Poultry'.

Figure 5a). A broiler chicken approaching a waterbath stunner. b) As the bird makes contact with the entry ramp its body is held back, facilitating thereafter a swift swing into the electrified water. The bird's wings are closed, reducing the risk of pre-stun shocks.

Figure 6. Use of an angled entry ramp to reduce pre-stun shocks.

Birds must be monitored as they move over an entry ramp. For example:

• If a shackle line descends as it passes over a ramp, then a large, heavy bird’s head and neck can become trapped between its body and the ramp, whilst the leading wing dips into the electrified water. For this reason, ideally, a shackle line should remain horizontal (or should not descend too much) at the entrance to a waterbath, to enable the entry ramp to work.
• Whilst the legs continue advancing at the pre-set speed of the shackle line, when the birds’ bodies contact the ramp their movement over it typically slows and their bodies, necks or shackles may overlap. Birds must be monitored to ensure they are not vigorously struggling, smothering one another, or that toes or feet do not become caught if the shackles cross over one another.
• As a bird enters a waterbath, its shackle must not overlap another shackle (whether occupied or unoccupied) because the bird’s shackle will not be in direct contact with the earthed rubbing bar and may compromise the flow of current for each bird.
• Small birds must not be shackled because they may fail to contact the entry ramp, not swing into the water and thereafter may continue to avoid the electrified water. Birds that are of an inappropriate size for effective stunning in a particular waterbath must be slaughtered using an alternative humane stunning method (eg the back-up device).

Next: Summary of pre-slaughter handling & restraint