Electrical currents applied to poultry through an electrical waterbath

A bird may be electrically stun-killed by applying a current at a frequency and amplitude that causes unconsciousness and simultaneously stimulates cardiac muscle into ventricular fibrillation resulting in death by cardiac arrest in a stunned bird. The birds are inverted and shackled before being passed through an electrified waterbath stunner (Figure 10). The birds are stunned and killed simultaneously as electrical contact is made between the live water and earthed metal shackle. When the head of a bird enters electrified water, the electrical circuit is completed. The current flows from the submerged electrode in the waterbath through the water and head of the bird, through the body and legs, to the metal shackle in which the bird is restrained and finally via the earthed rubbing bar.

Figure 10: Illustration of poultry suspended from shackles in waterbath stunner.

The electrical parameters (voltage, current, frequency and waveform) of a waterbath system can be set to either stun or stun-kill the birds. During a kill for disease control, stun-kill is preferable in terms of efficiency and biosecurity. Table 5 displays the recommended parameters for stunning and killing poultry using an electrical waterbath. Note, the values provided in this table are higher than in the Electrical Waterbath Stunning of Poultry online guide. When killing for disease control meat quality is not a consideration and so current should be increased in order to ensure all birds are dead upon leaving the waterbath.

As with all methods, birds should be assessed to ensure they have been killed effectively. If there is any doubt, they should be killed immediately using another method such as captive-bolt or cervical dislocation.

Table 5: Minumum parameters required to stun and kill poultry using an electrical waterbath.

NB: Figures provided for chickens: Gerritzen et al 2006. Turkeys and ducks: M Gerritzen pers comm. 2014.

For more detailed information regarding the use of electrical waterbaths with poultry please see the HSA electronic publication Electrical Waterbath Stunning of Poultry

http://www.hsa.org.uk/electrical-waterbath-stunning-of-poultry-introduction/introduction-7

Considerations when using electricity during depopulation due to disease control

The main advantage of using electricity to kill birds during a disease outbreak is that the head and body of the bird remains intact – it is a non-invasive method. This is particularly important when dealing with infected birds as the risk of disease spread is reduced. This method of stunning and killing the birds simultaneously is suitable for use with large numbers of birds.

There are some disadvantages to the use of this method on farm, as it requires specialised, equipment and a reliable supply of electricity at the killing area is essential. The birds need to be caught, handled and transported from their housing to the killing site, which increases the risk to human handlers if the birds are infected with a zoonotic disease. Manual restraint, bird inversion and shackling can also raise welfare concerns particularly with unfit birds. Waterfowl may be particularly difficult to stun/kill effectively with an electric waterbath as they are able to curl their necks, lifting their heads above their breast. If the chest makes contact with the electrified water before the head, there is a risk the duck may experience current flow without loss of consciousness because the brain is unlikely to be in the path of current flow. Regardless of species, if the birds’ wings or beaks enter the water first there is also a risk of pre-stun shocks which cause pain and can prevent effective stunning. This will be inhumane. Currently there is limited evidence on the recommended settings for use with waterfowl and therefore alternatives to this method may be more suitable for these species.

Conclusion – species and situations

This method is suitable for use with large numbers of birds such as quails, chickens, ducks, geese and turkeys. However, as welfare problems may arise when using waterbath stunning on waterfowl, alternative means may be better suited to the humane killing of these animals. As electrical stun/killing of poultry requires specialist equipment, gas may be a better alternative for killing large numbers of birds during a depopulation.

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