Effectiveness Of Electrical Stunning Research Articles

The effects of electrical stunning on the nervous activity and physiological stress response of a commercially important decapod crustacean, the brown crab Cancer pagurus L.

Increasing attention is being paid to the welfare of decapod crustaceans. Legislation exists for their humane slaughter in several countries and this is being debated in others. Electrical stunning may have potential for humane slaughter of crustaceans in some circumstances, although scientific data on the effectiveness of electrical stunning when applied to various species are limited. Assessment criteria for effective stunning have so far been based mainly on behavioural assessments, but these do not always reflect neural insensibility. In this study direct recordings of neural activity, both centrally and peripherally, have been used to provide more direct measures of the state of sensibility. We have also examined whether electrical stunning acts as a physiological stressor, using measures of haemolymph L-lactate. Experiments were performed on a commercially important decapod species, the brown crab Cancer pagurus L. Spontaneous activity within the CNS was arrested by electrical stunning, which is an indication of loss of sensibility. There were also specific effects on the peripheral nervous system, with loss of responsiveness to sensory stimulation, rendering the animals unresponsive to external stimuli, and a failure of motor activation. All these effects were apparent immediately after a 10s stun, and persisted for as long as tested (4h) indicating that the animals were also killed by the procedure. No autotomy of limbs occurred. Haemolymph L-lactate was found to be no greater following electrical stunning than after handling and sampling alone, and both were significantly lower than values reached in a range of environmental and commercial situations. For all these reasons we find that electrical stunning may meet criteria for humane slaughter of C. pagurus.

Review Of The Main Welfare Risks Related To Electrical Stunning Of Small Ruminants (Ovine And Caprine Species)

EFSA commissioned a comprehensive review of the welfare aspects of electrical stunning methods for small ruminants with an emphasize on low ampere stunning to establish the state of the art in the field and to assess whether scientific studies would address criteria outlined in an EFSA guidance on the assessment criteria for studies evaluating the effectiveness of stunning interventions regarding animal protection at the time of killing (EFSA Journal 2013;11(12):3486). The review was not formulated as a systematic review with a focused question instead the review followed the approach to assessing the literature described by the EFSA guidance. The key databases searched were: Science Citation Index (1900-2014), CAB Abstracts (1910-2014) and Medline (1990-2014). Key conferences proceedings and the bibliographies of review articles were manually searched. The search yielded 1599 records. 706 duplicate records were removed and 894 records assessed for relevance. Relevant studies reported electronic stunning of small ruminants and outcomes associated with onset and duration of unconsciousness. Eighteen papers reported electrical approaches to stunning in sheep. No goats were studied. None of the papers reported all of the parameters detailed in the EFSA guidance (EFSA, 2013) and a risk of bias assessment was not conducted. No studies reported the appearance of the electrodes. When the frequency (Hz) applied to the animal was reported, it was not specified whether this represented a minimum or maximum frequency. Only one study explicitly reported an effect size for amperes. The study suggested that the odds of a poor stun were higher for amperes of 0.6 (odds ratio (OD) of 6.27 with 95% confidence interval (CI) of 1.98-20.7) and 0.8 (OR of 24.4 with 95% CI of 6.98-85.2) when compared to a poor stun at 1.25 ampere. © European Food Safety Authority, 2015

The effects of electrical stunning and percussive captive bolt stunning on meat quality of cattle processed by Turkish slaughter procedures

The effects of electrical and percussive captive bolt stunning both on initial and up to 14 days post mortem meat quality of Friesian young bulls were studied. The first group (NS; n=10) were slaughtered without stunning under Turkish slaughter procedure (these animals were slaughtered under conditions acceptable to the appropriate ethics committee) in a modern abattoir. In the second group (ES; n=10) animals were electrically stunned. In the third group (PS; n=10) animals were stunned with percussive captive bolt. Meat quality was assessed by examining muscle glycogen concentration, pH and WHC. Also cooking loss, texture parameters and consumer sensory properties were assessed at 24 h, 4, 7 and 14 days post mortem. Meat colour as L ∗, a ∗, b ∗, C ∗, h ∗ values were evaluated at 0, 48 h, 3, 5, 7, 9 and 14 days post mortem. Pre-slaughter handling affected muscle glycogen concentration ( P<0.05). Animals in electrical and percussive captive bolt stunned groups had higher muscle glycogen concentrations compared to animals in the non-stunned group ( P<0.05). Although pre-slaughter handling did not affect significantly pH 24 h and WHC, differences were significant for cooking loss, colour coordinates and texture parameters at some storage times. For all sensory attributes (odour, flavour, tenderness and overall acceptability) at all ageing periods (24 h, 4, 7 and 14 days) the percussive stunned (PS) group was significantly superior to the non-stunned (NS) group. The electrically-stunned (ES) group also tended to be superior to the NS group although not all differences were statistically significant. These results indicate that percussive captive bolt stunning of cattle improved meat quality compared with cattle electrically stunned using head only tongs and those non stunned under approved Turkish slaughter procedure.

A critical appraisal of electrical stunning in chickens

Chickens, unlike red meat species, do not show grand mal epilepsy in the brain following electrical stunning. The underpinning causes of this and the brain mechanisms associated with the induction and maintenance of electrical stunning induced unconsciousness in chickens have not been elucidated. However, the changes occurring in the electroencephalogram (EEG), abolition of somatosensory evoked potentials (SEPs), induction of seizure and loss of muscle tone or physical reflexes following electrical stunning have been used in the past to ascertain the effectiveness of waterbath electrical stunning in chickens.The purpose of this appraisal is to evaluate scientifically the relative merits of some of the criteria that have been used for ascertaining the effectiveness of electrical stunning in chickens. Scientific literature suggests that, unlike red meat species, the electrical stunning-induced release of monoamines and inhibitory amino acid neurotransmitter(s) in the chicken brain may play prominent roles in the induction and maintenance of unconsciousness following electrical stunning. These mechanisms would also appear to be relevant to the manifestation of a profoundly suppressed EEG and abolition of SEPs following electrical stunning, which are suggested to be meaningful indicators of an effective electrical stunning in chickens.

Rigor mortis development in turkey breast muscle and the effect of electrical stunning

Rigor mortis development in turkey breast muscle and the effect of electrical stunning on this process are not well characterized. Some electrical stunning procedures have been known to inhibit postmortem (PM) biochemical reactions, thereby delaying the onset of rigor mortis in broilers. Therefore, this study was designed to characterize rigor mortis development in stunned and unstunned turkeys. A total of 154 turkey toms in two trials were conventionally processed at 20 to 22 wk of age. Turkeys were either stunned with a pulsed direct current (500 Hz, 50% duty cycle) at 35 mA (40 V) in a saline bath for 12 seconds or left unstunned as controls. At 15 min and 1, 2, 4, 8, 12, and 24 h PM, pectoralis samples were collected to determine pH, R-value, L* value, sarcomere length, and shear value. In Trial 1, the samples obtained for pH, R-value, and sarcomere length were divided into surface and interior samples. There were no significant differences between the surface and interior samples among any parameters measured. Muscle pH significantly decreased over time in stunned and unstunned birds through 2 h PM. The R-values increased to 8 h PM in unstunned birds and 24 h PM in stunned birds. The L* values increased over time, with no significant differences after 1 h PM for the controls and 2 h PM for the stunned birds. Sarcomere length increased through 2 h PM in the controls and 12 h PM in the stunned fillets. Cooked meat shear values decreased through the 1 h PM deboning time in the control fillets and 2 h PM in the stunned fillets. These results suggest that stunning delayed the development of rigor mortis through 2 h PM, but had no significant effect on the measured parameters at later time points, and that deboning turkey breasts at 2 h PM or later will not significantly impair meat tenderness.

Effectiveness of different electrical stunning regimens for turkeys and consequences for carcase quality

1. This study examined the effectiveness of electrical stunning of turkeys applied at 150 mA per bird utilising a range of waveform-frequency combinations. In addition, the effect of stunning treatment on subsequent carcase quality was examined. 2. The effectiveness of stunning, as judged by time to recovery, was similar regardless of bird weight or applied stunning treatment. 3. Increasing waveform frequency was associated with a decrease in the prevalence of ventricular fibrillation, although turkeys appeared more susceptible than broilers. 4. Use of the higher frequency waveforms (500 and 1500 Hz) was associated with a marked improvement in carcase quality, particularly with regard to breast muscle haemorrhaging and their use may result in considerable commercial advantage.

Effectiveness of electrical stunning applied using a variety of waveform-frequencycombinations and consequences for carcase quality in broiler chickens

1. The effectiveness of electrical stunning of poultry was assessed where the recommended current of 105 mA per bird was applied using a range of waveform-frequency combinations. In addition the effect of the treatments on subsequent carcase quality was investigated. 2. The use of frequencies greater than 50 Hz was associated with a failure to induce ventricular fibrillation. 3. All waveform-frequency combinations were equally effective in producing a stunned state; the time to recovery was not affected by stunning treatment but was significantly longer in heavier birds. 4. The use of high frequency (500 Hz and 1500 Hz) stunning currents resulted in a decrease in carcase downgrading and a marked reduction in the occurrence of breast muscle haemorrhages, which represent significant commercial benefits to be gained by their use.

Electrical head-only stunning of fallow deer (Dama dama)

Abstract We recently published a paper(1) documenting the success of head-only electrical stunning in red deer (Cervus elaphus). This work has now been extended to fallow deer (Dama dama) to determine whether there are differences between this species and red deer in terms of behavioural responses and effectiveness of electrical stunning.

Effect of incomplete immersion of the head in waterbath stunners on the effectiveness of electrical stunning in ducks

Ten ducks were subjected to electrical stunning with their heads completely immersed in the water of a water-bath, and 10 ducks received the same current while only the bill and skin over the crop made contact with the water. The effect on visual evoked responses in the brain was examined. A higher proportion of birds had lost their visual evoked responses immediately following the current with whole head immersion. It is suggested that crop and bill immersion is less effective in disturbing brain function than whole head immersion.

Effect of wetting a chicken's feathers on the effectiveness of electrical stunning

Chickens were electrically stunned either when their bodies and feathers were wet or when they were dry. The time to recovery of muscular activity following stunning with 81 mA was assessed, and it was found that it was quicker in the wet birds. When hens which had previously been implanted with electroencephalogram electrodes were stunned with 119 mA it was found that the prevalence of somatosensory evoked responses during the first 60 seconds after applying the current was not significantly influenced by the wetness of the birds. It was concluded that electrical stunning with low currents in wet birds leads to a lower prevalence of ventricular fibrillation at stunning and a shorter lasting stun in the non-fibrillated birds. This effect is possibly due to some of the current tracking over the bird's wet body rather than through the brain.

Effect of depth of immersion in the waterbath on the effectiveness of electrical stunning in chickens

Broiler chickens were electrically stunned either by immersing their heads, necks and upper breast in a waterbath stunner or by immersing their heads only. The time to recovery of muscular activity was assessed, and it was found that the deeper immersion was associated with a slightly (10 second) shorter time to resumption of head righting. When hens which had previously been implanted with electroencephalogram electrodes were electrically stunned it was found that the incidence of somatosensory evoked responses during the first 60 seconds after applying the current was not influenced by the depth of immersion. It was concluded that depth of immersion had little influence on the effectiveness of electrical stunning.

Effects of Electrical Stunning and Hot Deboning on Broiler Breast Meat Quality

The effects were determined of electrical stunning prior to death and hot deboning on pH, percent weight loss due to cooking, and objective tenderness of broiler breast meat. Forty-eight live broilers were obtained from a processing plant and transported to the pilot plant facility of the research center. Half the birds were electrically stunned prior to death, and half were not. Birds were processed in the following manner: bled by outside neck cut for 2 min, scalded for 2 min at 53 C, feathers removed, and left pectorialis major immediately removed. The remainder of carcass was eviscerated, head, neck, and feet removed, prechilled, stored for 24 hr at 2 C, and right p. major removed. The pH was taken at the time of muscle removal, the skinless p. major weighed, cooked in water at 88 C to 82 C, cooled, and weighed. A 2.5-cm wide strip was removed to measure objectively tenderness as force to shear. The entire procedure was replicated twice.There was a significant stun by age interaction for pH and percent weight loss due to cooking. Breast meat from birds stunned prior to death exhibited higher pH 20 min postmortem than meat from nonstunned birds. Stunning had no effect on ultimate postmortem pH. Breast meat cooked 20 min postmortem exhibited lower percentage weight loss than meat cooked 24 hr postmortem. The meat cooked 20 min postmortem exhibited significantly higher shear values–it was less tender–than meat cooked 24 hr postmortem. Postmortem aging had a more pronounced effect on objective texture than electrical stunning.

The effect of electrical stunning and slaughter on the electroencephalogram of sheep and calves

To study the application of electroencephalography (EEG) for the assessment of insensibility during stunning and slaughter, recordings were made on sheep that were slaughtered by throat cutting, electrically stunned head-only and allowed to recover, electrically stunned head-only followed by throat cutting or electrically stunned head-to-back. The same experiments were repeated on calves (1–6 weeks old) except some calves were stunned and allowed to recover before final stunning and throat cutting. After the throat cut, sheep became insensible (i.e. EEG < 10 μV) at 8–22 s but the calf EEG did not fall below 10 μV until 79 s after the cut. With head-only stunning/recovery, high-amplitude EEG waves (electroplectic fit) continued for 47 s (sheep) and 33 s (calves) post stun. A quiescent period followed, which then developed into a period of moderate-amplitude EEG signals, so that, at 50 s post stun, the EEG usually exceeded 50 μV and often had bursts of 150 μV activity. After head-only stunning/throat cutting, the electroplectic fit was shortened (39 s in sheep, 23 s in calves) and the EEG took at least 50 s to fall below 10 μV. With sheep stunned head-to-back, which stops the heart, and thus should cause immediate, permanent insensibility, the EEG took longer to fall below 10 μV (52 s) than after throat cutting. These results suggest that electrical stunning of sheep and calves causes a prolonged increase in the post-stun EEG amplitude. Therefore, during slaughter, stunned animals have larger amplitude EEG signals than unstunned animals, and EEG criteria developed for judging the sensibility of unstunned animals cannot be used for those that are electrically stunned.