Electroencephalographic studies of calves associated with electrical stunning, throat cutting and carcass electro-immobilisation

Electroencephalographic (EEG) recordings were made on 34 calves (two days to six weeks old, 30-50 kg) during the slaughter process. The calves, supported in a V-shaped box or polypropylene net, were either head-only electrically stunned (50 Hz, 1.0 A) across the head and allowed to recover, head-only stunned followed by throat cutting or head-only stunned followed by throat cutting and electro-immobilisation. All time intervals were measured from the commencement of the stun. The electro-immobilisation (80 V peak, 14.3 Hz, 5 ms square wave) at 15-26 seconds post-stun was applied through electrodes attached to nose and anus, for periods ranging from 5-60 seconds. The head only stun produced an elevated EEG amplitude of the electroplectic fit which lasted approximately 34 seconds followed by a quiescent period before the EEG amplitude again became elevated above normal. A normal pre-stun pattern was not reached until many minutes had elapsed. Following the stun, the forelegs were usually flexed and then extended, gradually becoming part of the paddling movements commencing as early as eight seconds post-stun. Such movements were taking place while the animal was still stunned. With a head-only stun followed by throat cutting, the electroplectic fit was reduced to about 23 seconds and the amplitude of the EEG fell to about 10 microV after 50-73 seconds and breathing was inhibited for at least 20 seconds after stun commencement. If inadvertently only one carotid was severed, the EEG did not fall as rapidly as when both carotids were cut. The increase in amplitude of the EEG tracings was caused by stunning but the reduced duration of this increase in calves in which the throat was cut, suggests that there is an impairment of recovery of brain function from the moment of cutting and recovery of sensibility is unlikely. In reviewing the criteria of sensibility, we believe that insensibility can be presumed to continue from stun initiation, through the throat cut until the EEG falls below 10/microV provided that there is no resurgence of activity and the EEG amplitude continually falls rapidly enough. By this criteria, calves which are electrically stunned and rapidly exsanguinated remain permanently and irreversibly insensible. The addition of at least 15 seconds electro-immobilisation causes an even more rapid fall in the amplitude of the EEG (<10 microV at 50 seconds) making insensibility more certain as well as abolishing animal movement.     

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 after 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 turkey hens 12 weeks of age were surgically implanted with EEG recording and left wing nerve stimulating electrodes 4 hours before stunning. They were individually stunned by immersion of the head and upper part of the neck in a water bath for 4 s. Using a 150-mA current, all birds stunned at 50 Hz showed cardiac arrest and a flat EEG immediately after the stun with no SEP recovery. The incidence of cardiac arrest at stunning decreased with increasing current frequency but SEP were lost in all birds. In birds that survived the stun, the duration of SEP abolition was on average 69 and 34 seconds at 300 and 600 Hz, respectively. Stunning with a 75-mA AC, delivered with 50 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 duration of SEP of 66 seconds. The results indicate that increasing the frequency of a 150-mA AC current leads to a decreased stunning efficiency. A current of 75 mA per bird is unacceptable since 29 per cent of the birds do not show SEP abolition.     

Electrical stunning of cattle

Cattle are normally stunned electrically by three sequential cycles, first a three-second head-only cycle, to stun the animal, secondly a 15-second cardiac cycle, to induce ventricular fibrillation (cardiac arrest), and thirdly a four-second discharge cycle, to reduce convulsions after death. An effective and immediate stun was produced when > or =1.15 amps sinusoidal AC at 50 Hz was applied between the nose and neck electrodes for less than one second. However, when applied for three seconds, head-only currents of >0.46 amp sinusoidal AC at 50 Hz were sufficient to induce epileptiform activity in the brain, identified as high amplitude low frequency activity in the electroencephalogram. The induction of effective head-only electrical stunning resulted in an average interval of 50 seconds before the return of rhythmic breathing movements, and positive corneal and palpebral reflexes. The cardiac arrest cycle successfully induced ventricular fibrillation when >1.51 amps sinusoidal AC at 50 Hz was applied for five seconds between the nose and brisket electrodes.     

Electrical stunning of red deer (Cervus elaphus)

Eighteen of 23 red deer (Cervus elaphus) at a deer slaughtering premises were successfully stunned with an apparatus modified from that normally used to stun sheep. The five unsuccessful electrical stuns were associated with poor head restraint and poor head contact by the electrodes. The median stunning current was 0.9 A, and in the majority of cases the duration of stunning was less than 1 second. The signs of the electrically induced epileptiform seizures in the deer were dissimilar to those seen in sheep, cattle and pigs, in that the initial tonic phase was less marked, and of shorter duration. A similar shorter and less obvious tonic phase was noted in four deer shot with a captive bolt pistol. Two animals which were electrically stunned, and bled within 10 seconds, showed no signs of recovery while bleeding. The electroencephalograms of four deer stunned with currents of 1.3 A for a duration of either 0.5 or 1.0 seconds were recorded under more controlled conditions. All four animals developed electroencephalograms typical of an epileptiform seizure. The animals exhibited behavioural reactions similar to the other 18 animals in the trial at the deer slaughtering premises and were rendered unconscious for between 54 and 122 seconds. The electroencephalogram activity amplitude was greater than that recorded immediately before stunning and took between 6 and 9 seconds to build up to maximum value. It is concluded that, providing the heads of deer are adequately restrained, head-only electrical stunning can be incorporated into a humane method of slaughter for deer.     

The use of electrical stunning followed by electro-immobilization for the humane slaughter of cattle

Sir;- In New Zealand, calves are often electrically stunned before slaughter. However, electrical stunning is not usually used for adult cattle, primarily because the large size of the adult animal makes restraint more difficult, resulting in less reproducible stunning, with potential danger to personnel from animal movement. In addition, the slaughter of cattle may be inhumane if the stunning process does not ensure immediate and permanent insensibility (Newhook and Blackmore 1982b). The use and humaneness of electrical stunning of sheep and cattle have been the subject of our recent research, in which we have addressed and resolved many of these problems. We wish to relate our observations in the context of head-only electrical stunning of cattle followed by electro-immobilization to maintain insensibility and ensure carcass stillness.     

An evaluation of the effectiveness of handheld stunners for stunning chickens

Two experiments were conducted in which the spontaneous physical behaviour, spontaneous electroencephalogram (EEG) and somatosensory evoked potentials were examined in chickens stunned with a handheld, head-only stunner operating at 117 v. Thirteen of 14 birds lost their evoked potentials after stunning, and when they were exsanguinated within 15 seconds they did not regain them before they died. The remaining bird appeared to have evoked potentials after stunning but there was a movement artifact in its EEG and it is possible that they were not genuine responses. When head-only stunning was applied to 50 birds for one second the birds appeared to be stunned instantaneously, in terms of their spontaneous physical behaviour. However, they recovered more rapidly than 40 birds which were stunned for seven seconds. It was concluded that the handheld stunner can stun a bird effectively, and provided that the bird's neck is cut promptly, can kill it humanely.     

Physiologic reactions during the slaughter of cattle and sheep with and without stunning

In a first trial the cortical activity of cattle and sheep was tested using only an electrocorticogram (ECoG). The results showed a shorter phase after sticking or the ritual slaughter cut respectively, until the ECoG disappears in stunned animals. However, considering the time between stunning and the cervical state, the interval until disappearance of the ECoG was prolonged in the stunned animals. The observed time differences, however, are only a tendency and not statistically confirmed. Insofar, concerning animal protection, the different slaughter methods could be regarded equivalent. A second trial was designed in a manner to allow a more exact interpretation of the ECoGs and was completed by measuring visually and somatosensorically evoked potentials. Additionally, in contrast to the first trial, only adult cattle were used here. The results revealed shorter intervals until disappearance of cortical activities when using captive-bolt stunning. Also the variance was much lower in this trial than after ritual slaughter. The mean of the time differences was relatively low (5.5 seconds). It was especially remarkable that after captivebolt stunning absolutely no evoked potentials could be registrated, whereas these potentials lasted for 77 seconds (somatosensorically evoked potentials) and 55 seconds respectively (visually evoked potentials) after the ritual slaughter cut. Thus, after ritual slaughter a nervous conduction was measured up to 126 seconds in the extreme cases. However, from the results obtained it can not be concluded whether or not pain sensitivity occurred in the animals.     

Effects of electrical water bath stunning current frequencies on the spontaneous electroencephalogram and somatosensory evoked potentials in hens

1. The effectiveness of water bath electrical stunning of chickens with a constant root mean square (rms) current of 100 mA per bird delivered for 3 s using 100, 200, 400, 800 and 1500 Hz sine wave alternating current (AC) was investigated in layer hens. The quantitative changes occurring in the electroencephalogram (EEG) and somatosensory evoked potentials (SEPs) were used to determine the effectiveness of stunning. The changes occurring in the EEG were evaluated using Fast Fourier Transformations (FFT) and the SEPs were averaged to determine whether they were present or abolished. 2. The results of FFT indicated that stunning of chickens with a constant rms current of 100 mA per bird using 100 or 200 Hz induced epileptiform activity in all the hens, immediately followed by a reduction in the total (2 to 30 Hz) and relative (13 to 30 Hz) power contents in the EEG frequency bands indicative of unconsciousness and insensibility. The SEPs were abolished in the majority of hens stunned with 100 Hz and all the hens stunned with 200 Hz. 3. By contrast, stunning using 400, 800 or 1500 Hz failed to induce epileptiform activity in all the birds, the total and relative power contents in the EEG frequency bands showed a substantial increase, rather than reduction, and the SEPs were also retained in the majority of chickens. It is therefore suggested that stunning using these frequencies failed to stun them satisfactorily. In these birds, occurrence of a painful arousal, rather than unconsciousness, could not be ruled out. 4. It is therefore suggested that water bath electrical stunning of chickens with a minimum rms current of 100 mA per bird delivered using 100 or 200 Hz would be adequate to ensure bird welfare under commercial conditions, provided both the carotid arteries in the neck are severed at slaughter. On humanitarian and bird welfare grounds, a rms current of greater than 100 mA per bird should be applied whilst using frequencies of 400 Hz or more of sine wave AC for water bath electrical stunning of chickens.     

Cortical function in cattle during slaughter: conventional captive bolt stunning followed by exsanguination compared with shechita slaughter

Brain function was examined in adult cattle after conventional captive bolt stunning or shechita slaughter, using eight animals in each treatment. The times to loss of evoked responses (visual and somatosensory) and spontaneous activity in the electro-corticogram were used to determine the onset of brain failure. Captive bolt stunning followed by sticking one minute later resulted in immediate and irreversible loss of evoked responses after the stun. Spontaneous cortical activity was lost before sticking in three animals, and in an average of 10 seconds after sticking in the remaining five animals. The duration of brain function after shechita was very variable, and particularly contrasted with captive bolt stunning with respect to the effects on evoked responses. These were lost between 20 and 126 seconds (means of 77 seconds for somatosensory and 55 seconds for visual evoked responses) and spontaneous activity was lost between 19 and 113 seconds (mean 75 seconds) after slaughter.     

Non-penetrative percussion stunning of sheep and calves

Attempts were made to stun lambs, adult sheep and calves by a non-penetrative percussive method. Using an adapted Cash pistol, with a concave padded impact head, impulses were produced which effectively stunned 96% of lambs but induced brain haemorrhages in up to 7% of the animals. The signs and duration of an effective percussive stun were observed and recorded. Calves were readily stunned by percussive methods but brain haemorrhages frequently occurred. Impulses sufficiently large to stun adult sheep, with a non-penetrating impact head, were produced from an adapted Hantover pneumatic cattle stunner. Comparative trials, using electrical and percussive stunners, demonstrated a significant decrease in the prevalence of blood splash in lambs stunned by percussion.     

Observations during captive bolt stunning of rabbits]

78 rabbits of mixed breed and about 3 kg live weight were stunned before slaughter with a commercial spring operated captive bolt apparatus designed for rabbits and water fowl. The following reaction patterns were observed: 1.) Immediate onset of tonic spasm, followed by weak to heavy clonic spasms and/or subsequent relaxation; irreversible loss of corneal reflex and cessation of respiration: effective and irreversible stun tantamount to killing 2.) Same reaction as before except that respiration restarted after 1/2 to 2 min: effective but only temporary stun 3.) Similar reaction as before, but respiration maintained: insufficient stun 4.) Immediate onset of weak tonic spasm; respiration and corneal reflex maintained: insufficient stun. According to this classification 56 rabbits (72%) were killed outright and 18 (23%) temporarily stunned while in 4 (5%) the stun was ineffective. The captive bolt apparatus proved thus to be principally suited for the stunning resp. killing of slaughter rabbits. The best stunning results were obtained with shots into the parietal bone near the sagittal line but not hitting the bone sutures. To achieve this the apparatus has to be placed slightly paramedian on the front as close to the ears as possible. Insufficient stunning results could be blamed on deviating shooting positions. To avoid misses a good fixation of the animal including its head is necessary. Correct application provided the use of penetrating concussion stunners should be preferred to applying a blow to the neck for stunning rabbits.     

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.     

Head-cloaca controlled current stunning: assessment of brain and heart activity and meat quality

1. Behavioural and neural responses of 65 broilers to head-to-cloaca electrical stunning were evaluated and meat quality was assessed on two groups of 25 broilers stunned either head to cloaca, or in a conventional water bath method.

2. On the EEG recordings, a general epileptiform insult was observed when applying a current of 100?mA (100?Hz) or 70?mA (70?Hz) for 1·5?s. This general epileptiform insult shows a tonic, clonic and exhaustion phase followed by spikes of alpha, beta, theta and delta waves with duration of on average 34?±?12?s and 39?±?23?s respectively. These birds may have been unconscious for 20?s or longer, according to the correlation dimension analyses.

3. The heart rate decreased significantly (P? 4. Within a confidence limit of 95%, taking into account the number of animals with a reliable EEG, the chance of an effective stun of all broilers lies between 0·9 and 1·0?with a current of 70?mA (100?Hz for 1·5?s; n?=?28) and with 100?mA (100?Hz for 1·5?s; n?=?27).

5. The shear force of breast fillets was slightly lower (P? 6. It can be concluded that broilers are effectively stunned with the head-cloaca method by using a controlled current of 70?mA or 100?mA for 1·5?s. The fillets and legs of bird stunned head-cloaca showed fewer blood splashes in the muscles compared with birds stunned in a conventional water bath.     

Return-to-sensibility problems after penetrating captive bolt stunning of cattle in commercial beef slaughter plants

OBJECTIVE: To evaluate efficacy of penetrating captive bolt stunning of cattle in commercial beef slaughter plants and identify potential causes of a return to sensibility among stunned cattle. DESIGN: Observational study. SAMPLE POPULATION: 21 federally inspected commercial beef slaughter plants. PROCEDURE: In each plant, stunning of at least 100 cattle (19 large plants) or a minimum of 1 hour of production (2 small plants) was observed, and cattle were evaluated for signs of returning to sensibility on the bleed rail. Cattle with a limp, flaccid head, a lack of spontaneous blinking, and an absence of a righting reflex were considered insensible. RESULTS: In 17 of the 21 (81%) plants, all cattle were rendered insensible before they were hoisted onto the bleed rail. The remaining 4 plants had cattle that had signs of returning to sensibility; these cattle were restunned prior to skinning or leg removal. Of 1,826 fed steers and heifers, 3 (0.16%) had signs of returning to sensibility, whereas 8 of 692 (1.2%) bulls and cows did. Return-to-sensibility problems were attributed to storage of stunner cartridges in damp locations, poor maintenance of firing pins, inexperience of the stunner operator (ie, shooting cattle too high on the forehead), misfiring of the stunner because of a dirty trigger, and stunning of cattle with thick, heavy skulls. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that efficiency of captive bolt stunning of cattle in commercial slaughter plants can be safely and objectively assessed. Care should be taken to maintain stunners correctly, particularly when stunning bulls and cows with heavy skulls.     

Head-only electrical stunning of poultry using a waterbath: a feasibility study

1. The objective of this work was to investigate the feasibility of head only waterbath stunning as a means of generating immediate and long lasting unconsciousness while preventing wing flapping and avoiding carcass damage. 2. EEG measurements showed that immersion of the heads of the broilers for one second in a waterbath containing water of conductivity 2 x 5 mS/cm and a 50 Hz electric field of 10 V/cm resulted in immediate unconsciousness, and that increasing the electric field strength extended the duration of unconsciousness. 3. The passage of a 25-30 mA alternating current of frequency 2000 Hz through the broilers' bodies suppressed the wing flapping that followed a stun. 4. When the body current and electric field were applied simultaneously, wing flapping was prevented and EEG signals were suppressed for over 30 seconds indicating that the immediate unconsciousness lasted long enough to facilitate humane slaughter.     

Changes in the release of amino acid neurotransmitters in the brains of calves and sheep after head-only electrical stunning and throat cutting

In calves aged two to five months, throat cutting resulted in an increase in the concentration of the amino acid neurotransmitters glutamate and aspartate in the brain. Electrical head-only stunning by itself also increased the concentrations of these two neurotransmitters. The levels induced by stunning resulted in a seizure state characterised by epileptiform-like activity in the electroencephalograph. Combing head-only stunning with throat cutting within 10 seconds of the stun had a synergistic effect upon glutamate and aspartate, increasing their concentration by a greater amount and more quickly than either procedure on its own. An irreversible loss of brain function also occurred more quickly than after throat cutting alone. The administration of glutamate and aspartate receptor antagonists before the throat cutting lengthened the time to the loss of brain function in a dose dependent manner. Similar changes were observed in sheep but they occurred much more quickly than in cattle.     

Efficiency of bleeding of broilers after gaseous or electrical stunning

The efficiency of bleeding of broilers (g blood/kg liveweight) was measured after stunning them with either 45 per cent carbon dioxide in air for two minutes or with 2 per cent oxygen (achieved by displacing air with argon) for two minutes or with an electric current (77 or 104 mA at 50 Hz for four seconds). The results indicated that the initial rate of bleeding was higher in the electrically stunned broilers with non-fibrillated hearts than in the gas stunned broilers and electrically stunned broilers with fibrillated hearts. This difference was significant up to 60 seconds after neck cutting (P less than 0.05) but after 140 seconds all the broilers had bled out to a similar extent (30 to 33 g/kg liveweight). It is concluded that after gas stunning the time interval between neck cutting and scalding should be 60 to 140 seconds.     

Effect of very low pulsed direct currents at high frequency on the return of neck tension in broilers

Broiler chickens were stunned electrically for one second or 10 seconds with a unipolar pulsed direct current (DC) at 550 Hz. The effectiveness of the stun was assessed from the birds' behaviour. All the birds were stunned effectively when more than 15 mA true root mean square DC was applied for either period. An increase in the duration of the applied current resulted in an increased duration of unconsciousness. However, the unipolar pulsed DC at 550 Hz did not induce cardiac arrest, and it must therefore be accompanied by a prompt and effective neck cut, severing both carotid arteries.     

Cattle stunning with a penetrative captive bolt device: A review

The captive bolt device has been used for stunning cattle at abattoirs for more than 100 years and is now one of the stunning devices used most widely. The aim of this review article was to assess the effects that are decisive during cattle slaughter on the quality of stunning with the use of a captive bolt stunning device. The basis of effective stunning is the use of a suitable type of device, with the speed of the bolt and the kinetic energy corresponding to the anatomical parameters of the slaughtered animal. The importance of the regular cleaning and maintenance of stunning devices and monitoring of the effectiveness of stunning goes without saying. The immediate loss of sensibility in the animal must occur after the first shot. The effectiveness of the stunning process can be quantified by regular monitoring of the behavior of animals after stunning with an emphasis on the loss of reflexes (corneal reflex, regular breathing, attempts to regain physiological posture) and checks on the shot location on the skulls of slaughtered animals.     

Head-only followed by cardiac arrest electrical stunning is an effective alternative to head-only electrical stunning in pigs

Many small slaughter facilities use head-only electrical stunning to render swine unconscious and insensible to pain before slaughter. Head-only electrical stunning is a reversible procedure that is optimally effective for approximately 15 s after stun completion. In many small North American slaughter plants, the authors have observed hoist speeds that are too slow to achieve a short enough stun-to-bleed interval to maintain insensibility through exsanguination. Unlike many European plants, there is no separate high-speed hoist for pigs and exsanguination on the floor is not condoned. As a result, a 2-stage stunning method was proposed where head-only stunning for 3 s was immediately followed by application of the same stunning wand to the cardiac region of the animal for 3 s while lying in lateral recumbancy. A paired-comparison study was conducted on 89 pigs in a small slaughter facility to compare the head-only method applied for 6 s with the head/heart method. The objective was to evaluate signs of return to sensibility, stun-to-bleed time, blood lactate concentration, muscle pH, drip loss, and fresh meat color to validate the head/heart electrical stunning method for small slaughter plants. Incidence of corneal reflex was not different (P > 0.05) between head/heart (93.8%) and head only (85%) stunning. Nose twitching was more common (P < 0.05) in head only (26.5%) than head/heart (5%) stunning. Head/heart stunning eliminated rhythmic breathing, natural blinking, eye tracking to moving objects, and righting reflex, which were all observed in head-only stunned pigs. Eye tracking to moving objects was observed in 40.8% of head-only stunned pigs. Blood lactate was not different (P > 0.05) between stunning methods (head only: 8.8 ± 0.7 mmol/L, head/heart: 7.8 ± 0.7 mmol/L). Stun-to-bleed time did not differ (P > 0.05; head only: 32 ± 1 s, head/heart: 33 ± 1 s). Mean time to loss of heartbeat with the head-only method was 121 ± 5 s. No heartbeat was observed with the head/heart method. Longissimus thoracis pH, color, and drip loss were not different (P > 0.05) between stunning methods. This study determined that the head/heart electrical stunning method reduces the incidence of signs of return to sensibility without significant effects on meat quality, plant operation speed, or blood lactate concentration. In addition, the head/heart method requires no capital investment for plants that are currently using the head-only method.