Assessment of the effectiveness of head only and back-of-the-head electrical stunning of chickens

Abstract

The study assesses the effectiveness of reversible head-only and back-of-the-head electrical stunning of chickens using 130–950 mA per bird at 50 Hz AC.Three trials were conducted to compare both stunning systems: (a) behavioural assessment of return of consciousness, (b) insensibility to thermal pain, and (c) assessment of return of brain activity with visually evoked potentials (VEPs).Assessment of behaviour suggested that the period of unconsciousness following head-only electrical stunning was shorter in hens compared to broilers.Stunning across the back-of-the-head delayed the time to return of brainstem function compared to stunning with standard head-only electrodes. Additionally, back-of-the-head stunning produced a more prolonged period of electroanalgesia compared to head-only.Based on examination of return of brain function with VEPs in hens, back-of-the-head stunning produced a shorter-lasting stun than standard head-only. However, even for standard head-only, the stun was notably shorter than previously reported. In some birds, brain function had returned within 9 s after the end of stunning.The results suggest that some birds may recover consciousness prior to or during the neck cut. Based on these findings, back-of-the-head stunning and standard head-only stunning of hens should not be recommended without further development.

Electroencephalographic assessment of concussive non-penetrative captive bolt stunning of turkeys

“…Apnoea after stunning has been associated with damage to the medulla and reticular formation. The absence of the nictitating membrane reflex is associated with brainstem dysfunction, and the lack of neck tension relates to loss of CNS control of muscle tone (Gibson et al, 2016, Terlouw et al, 2016.…”

“…There are many welfare concerns regarding waterbath stunning of poultry, due to the risks of pre-stun shocks, suboptimum stuns, stress and pain during inversion and suspension from shackles, variations in electrical current delivered to birds in multi-bird waterbath stunners and aspiration of waterbath water (EFSA, 2014, Hindle et al, 2010. Meanwhile research on head-only constant voltage electrical stunning of end of lay hens (Gallus g domesticus) reported that for some birds the period of induced insensibility only lasted 9 seconds (8.5 -31.5) seconds (Gibson et al, 2016). This could result in some hens recovering from the stun prior to, or during the bleeding process, resulting in significant pain and distress.…”

Pathophysiology of Concussive Non-Penetrative Captive Bolt Stunning of Turkeys

“…A significant proportion of these birds are slaughtered and processed by small-scale seasonal producers using head-only constant voltage stunning equipment [15]. With a widespread acknowledgment of the limitations of currently used constant voltage head-only electrical stunning systems [1,16] there has been a refocus on the captive bolt as an alternative method for small scale seasonal turkey producers.…”

“…Data from the left and right hemispheres were pooled to aid analysis. Severity of tissue damage to specific brain regions Immediately after shooting, all animals were assessed for clinical signs of sensibility, including the presence or absence of tonic and clonic convulsions, rhythmic breathing, nictitating membrane reflex, eyeball rotation, nystagmus, neck tension, and beak tension [1,4]. Eye-based reflexes were tested on both eyes.…”

“…Furthermore, research in chickens (Gallus g. domesticus) has reported that the duration of induced unconsciousness varied between birds, with some recovering within 9 s (range 9 to 31). This short period of recovery could result in some birds regaining consciousness during or prior to exsanguination [1]. An alternative stunning method is the non-penetrative captive bolt (NPCB).…”