Animal welfare aspects of poultry slaughter have been investigated by Drs Daniel L. Fletcher, Bruce Webster and Timothy L. Foutz of the University of Georgia and Dr R. Jeffrey Buhr of the USDA Russell Research Center in a project sponsored by the US Poultry and Egg Association.

Stunning is a key animal welfare issue and has been questioned regarding its status relative to humane slaughter, says the researchers. Most data is anecdotal and little objective data exist concerning the actual impact of electrical stunning on the animal. Of primary concern is that electrical stunning may not completely render the animal unconscious and therefore not completely insensible to pain or that stunning duration may not be sufficient to prevent the animal from regaining consciousness prior to death.

An animal behaviour model and electroencephalograms (EEG) were used to study the impact of electrical stunning on behaviour and EEG patterns. The rationale was based on the assumption that if electrical stunning immediately induced unconsciousness, the animal would not remember and would not develop an aversion to stunning as it might relative to a mild shock. Birds were either untreated (control), shocked, stunned or delay stunned and their behavior in repeated trials were observed. Control birds (no shock or stun) showed no response. All of the electrical treatments resulted in increased delay of approaching the feed (reward). Differences in the treatments were evident but were highly variable and indicate that repeated electrical treatments resulted in distinct behavioural differences from untreated controls. The EEG results show differences between treatments taken prior to and following treatment.

Although inconclusive, the results indicate that birds subjected to electrical stunning and allowed to recover developed some behavioural response compared to non-stunned controls. Although present, responses were less pronounced in the mild shocking and delayed stunning treatments.

Electrical stunning does result in some level of learned response and therefore cannot be considered to be totally benign.

However, caution should preclude over interpretations of these results since birds would normally not be subjected to repeated treatments, warned the researchers. The basis for the learned response is not clear. Furthermore, the test cannot distinguish between the acute effects of the stunning, as compared to shocking, versus the accumulated impact as compared to the control, they added.

October 2010