Parameters for stunning

When a stunning method is applied correctly, the stunning parameters should achieve an effective stun in 100% of individuals. Even a very small percentage of failed stuns will account for a large number of individual birds potentially suffering because poultry are slaughtered in vast numbers around the world.

Individual birds can be effectively stunned in waterbaths using a broad range of amplitudes of current, but the difficulty is ascertaining which parameters reliably achieve effective stunning in 100% of birds. EFSA (2012) could not identify any parameter combinations that, in all tests, resulted in 100% of birds being effectively stunned.

It does not appear possible to specify one current amplitude, for all frequencies and waveforms, that will ensure 100% effective stunning. Abattoirs should be aware that, to achieve an equivalent effect on a bird’s brain activity, different waveforms may require greater amplitudes of current.

In Europe, waterbaths must operate using electrical parameters specified by EC Regulation 1099/2009 (Table 3). However it should be noted that sine AC frequencies of 600 Hz or more, at 200 mA per bird, have failed to induce epilepsy and/or a sufficient duration of quiescent EEG in 100% of broiler chickens tested. Application of 100 - 200 mA per chicken, using frequencies higher than 200 Hz sine AC sometimes failed to induce sustained quiescent EEGs, especially at, and above, 800 Hz. Therefore, in the interests of bird welfare, it may be preferable to use frequencies of 50 - 200 Hz, maximum, for chickens and perhaps even for turkeys. Based on available research using EEG analysis of unconsciousness, the HSA suggests abattoirs consider using the additional measures in Table 4.

Table 3. Minimum current amplitudes per bird for electrical waterbath stunning, as required since January 2013 by European Council Regulation 1099/2009.

Table 4. Additional suggestions for good practice electrical parameters.

Hindle et al (2009) Electrical waterbath stunning of poultry Rapport 200: an evaluation of the present situation in Dutch slaughterhouses and alternative electrical stunning methods. Animal Science Group, Wageningen UR.

Guinea fowl 

There are no published recommended currents for inducing unconsciousness in 100% of guinea fowl. As a precaution, until scientific evidence becomes available, the HSA suggests that the minimum current amplitude might be at least 100 mA RMS per guinea fowl, at 50 Hz sine AC. Although the birds are relatively light in weight and have naked heads, they are older than some other species at the time of slaughter and so their skulls and thin legs may have developed a relatively high resistance to electricity.

Duration of application of electricity

To increase the likelihood of an effective stun and a prolonged duration of unconsciousness, each bird must be immersed in the electrified water for a sufficient time. The length of a waterbath and the line speed directly affect the duration that a bird is exposed to a current. The fastest line speed used by an abattoir must still be capable of administering the recommended minimum duration of current application. Recommendations include:

• At least four seconds (EC Regulation 1099/2009 and OIE, 2014)
• At least eight seconds when using high frequencies above 100 Hz (Defra, 2007)
• At least 10 seconds when using 50% pDC (Prinz, 2009)

Note: increasing the duration of application of current may only have a marginal effect on the efficacy of stunning and it cannot compensate for inadequate electrical parameters.

The electrical parameters intended for stunning each bird type should be recorded in the abattoir’s standard operating procedures (SOPs) and periodically reviewed and altered as necessary. All personnel responsible for assessing the effectiveness of stunning and for performing neck cutting must have seen the SOPs and be aware of the basic electrical requirements for each bird type (e.g. waveform, frequency, minimum required total current to the waterbath).

Next: Parameters for stun-killing