Effect of current frequency during electrical stunning in a water bath on somatosensory evoked responses in turkey's brain

Somatosensory evoked responses (SEP) in a turkey's brain were determined af ter water-bath stunning with a 150-mA (constant current) delivered with 50, 300 or 600 Hz, or with 75 mA, delivered with 50-Hz alternating current (AC ) in order to evaluate the effectiveness of stunning, Ninety-four BUT 9 tur key hens 12 weeks of age were surgically implanted with EEG recording and l eft wing nerve stimulating electrodes 4 hours before stunning. They were in dividually stunned by immersion of the head and upper part of the neck in a water bath fur 4 s. Using a 150-mA current, all birds stunned at 50 Hz sho wed cardiac arrest and a flat EEG immediately after the stun with no SEP re covery. The incidence of cardiac arrest at stunning decreased with increasi ng current frequency bur SEP were lost in all birds. In birds that survived the stun, the duration of SEP abolition was on average 69 atld 34 seconds at 300 and 600 Hz, respectively. Stunning with a 75-mA Ac, delivered with 5 0 Hz, induced cardiac arrest in 32 per cent of turkeys. SEP were abolished in only 71 per cent of the birds that survived the stun, with an average du ration of SEP Of 66 seconds. The results indicate that increasing the frequ ency of a 150-mA Ac current leads to a decreased stunning efficiency. A cur rent of 75 mA per bird is unacceptable since 29 per cent of the birds do no t show SEP abolition. (C) 2000 Harcourt Publishers Ltd.