The effects of amount and frequency of pulsed direct current used in water bath stunning and of slaughter methods on spontaneous electroencephalograms in broilers
The effectiveness of electrical water bath stunning of broilers (n = 96) for 1 s with a constant average current of 100, 150 or 200 mA delivered using a variable voltage/constant current stunner with 200, 800 or 1400 Hz pulsed direct current (DC), with a mark:space ratio of 1:1, followed
by slaughter using a unilateral or ventral neck cutting procedure, was evaluated. The results of a binary logistic model showed that both the electrical frequency and average current had significant effects on the probability of inducing epileptiform electroencephalogram (EEG) and therefore,
of effective stunning. The results of univariate analysis showed that only slaughter method had highly significant effects on the power contents in the 13–30 Hz and 2–30 Hz EEG frequency bands. Based on these results, it is recommended that a minimum of 200 mA average (400 mA peak)
current per bird should be delivered using 200 Hz pulsed DC, with a mark:space ratio of 1:1, to achieve effective water bath stunning in 80% of broilers. Frequencies of above 200 Hz pulsed DC would presumably require average currents of greater than 200 mA. Electrical water bath stunning of
broilers with 200 mA average current of 200 Hz resulted in cardiac arrest in six out of eight broilers that showed epileptiform activity. Two other broilers that had cardiac arrest showed no epileptiform EEGs indicative of effective stunning. Owing to the prevalence of cardiac arrest in conscious
broilers, the use of pulsed DC for water bath stunning of broilers could be questioned on ethical and bird welfare grounds.