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.     

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

1. 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.

2. 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).

3. Assessment of behaviour suggested that the period of unconsciousness following head-only electrical stunning was shorter in hens compared to broilers.

4. 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.

5. 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.

6. 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.

     

Effect of electrical stun/kill method, interval between killing and neck cutting and blood vessels cut on blood loss and meat quality in broilers

1. Broiler chickens were killed using either an electrical waterbath (WB system) delivering 120 mA per bird (50 Hz, alternating current, AC) for 4 s or an alternative stun/kill method (ASK system); where head-only stunning for 1 s was immediately followed by head-to-body (vent) application for 1 s (150 mA, 50 Hz sine wave AC). Within each stun/kill system, the neck was cut ventrally or unilaterally 20, 60, or 180 s after killing. In addition, a control group of broilers was stunned with 100 mA per bird in a waterbath using 1500 Hz AC for 4 s and were bled by a ventral neck cut within 20 s. 2. Blood leaving the neck cut was collected for 90 s in a bin placed on an electronic balance and blood loss (g/kg body weight) calculated. 3. Individually identified, unplucked and uneviscerated carcases were held at ambient temperature until the end of the experimental day and then stored overnight in an air chiller (5 degrees C). The carcases were dissected and the incidence of broken furculum and coracoid bones, haemorrhaging in P. minor and P. major muscles, and discolouration of P. major muscles were determined. 4. When neck cutting was performed in broilers 20 s after the stun or kill, the ASK and WB systems, in comparison with high frequency stunning, produced on average about 10 g per kg less bleed out. Within the stun/kill systems, broilers killed by ASK had a greater bleed out than in the WB system. Neck cutting at 20 s or 60 s post-kill resulted in a greater bleed out than when performed after a delay of 180 s. Ventral or unilateral neck cutting resulted in a similar bleed out. 5. Stunning broilers with 1500 Hz AC resulted in lower incidences of broken bones, haemorrhaging in breast muscles and muscle discolouration post mortem than the stun/kill systems. These defects were significantly lower in the ASK than in the WB system. Delayed neck cutting increased the severity of discolouration occurring Post mortem in the breast muscles. 6. It is suggested that broilers killed by ASK can be neck cut with a delay of up to 180 s without compromising bleed out. The incidence of broken bones and haemorrhaging in breast muscles are significantly less with ASK than WB. 7. Owing to the commercial benefits and potential for improved welfare at slaughter, ASK would appear to be a better method than WB.     

Electroencephalographic studies of adult cattle associated with electrical stunning, throat cutting and carcass electro-immobilization

Twelve adult cattle were electrically stunned head-only (400 V, 2.5 A, 50 Hz) behind the ears for four seconds. Within ten seconds of stun initiation, the carotid arteries, jugular veins, trachea and oesophagus were severed. Twenty seconds after the stun initiation, ten animals received an electro-immobilization current (80 V peak, 14.3 Hz, 5 ms square wave, 300 mA) nose to anus for periods ranging from 30-37 seconds. Electroencephalographic (EEG) traces were recorded before and after the stun up until electroimmobilization and at cessation of electro-immobilization by means of implanted electrodes, and animal movement was recorded on videotape. Before the stun, the EEG trace was within a window of sensibility (10-40 microV amplitude). During the stun, the amplitude increased and sometimes exceeded 500 microV. At the end of electro-immobilization, EEG amplitude was less than 10 microV, indicating insensibility. This amplitude was reached in the two non-immobilized animals 57 seconds and 63 seconds after stun initiation. During stunning, the forelegs and hindlegs usually tucked under the animals. Various degrees of foreleg extension then occurred. From about ten seconds post-stun, paddling movements occurred, at which time the EEG trace showed large-amplitude waves characteristic of a stunned animal. During immobilization, the animals stiffened and breathing stopped. After immobilization weak muscle spasms occurred that did not interfere with dressing operations. Non-immobilized animals moved excessively, inhibiting dressing. It is concluded that adult cattle rendered insensible by stunning do not recover sensibility during the stun/throat-cut/immobilization operation and therefore this procedure is humane.     

CO2-stunning of slaughter pigs: effects on EEG, catecholamines and clinical reflexes

Investigations were carried out on the response of slaughter pigs to CO2 stunning with two different gas concentrations (80 vol%, 90 vol%, 73 s) under practical conditions in a one gondola-dip-lift system. EEG measurements were performed and blood constituents such as catecholamines (adrenaline, nor-adrenaline) and lactate as well as clinical reactions (nasal septum and corneal reflex, heart beats) investigated. Special EEG-electrodes were adapted for the measurement on pigs and a mobile data logger was prepared for the use in the lairage of the slaughter house and in the stunning unit. The CO2 concentrations were measured continuously close to the head of the pigs when transported up and down in the stunning gondola. The results show that the technique is suited to monitor the effects of different CO2 gas concentrations on the EEG of the pigs under practical conditions. There is strong evidence that CO2 concentrations of 80 vol% applied over 70 s as required by law are not sufficient to stun pigs properly. A large part of the animals still showed typical reflexes when leaving the stunning pit. When an atmosphere of 90 vol% CO2 is applied, most animals are already dead before bleeding commences. This may create problems in respect to meat hygiene. The blood analysis revealed very high concentrations of catecholamines after stunning. The values for adrenaline and nor-adrenaline in the sticking blood rose by a factor of about 1000 as compared to the concentrations in blood samples taken in the lairage before stunning. It seems necessary to revise the current legislation on gas stunning and to look in greater detail in the effects of CO2 stunning on the welfare of slaughter pigs.     

The occurrence of reflexes and reactions in cattle following stunning with a captive bolt at the slaughterhouse

The difference in the frequency of the occurrence of reflexes/reactions in 355 cows (average weight 505.5 ± 7.9 kg) and 262 bulls (average weight 735.6 ± 8.4 kg) following stunning with a Matador SS 3,000 B trigger‐activated captive bolt gun (Termet) was determined. The stun shot more than 2 cm from the ideal position was found in 79.6% of animals. Vocalization, corneal reflex, rhythmic breathing, blinking, eyeball rotation and the absence of tongue protrusion occurred more frequently in bulls (p < .05). Spontaneous limb movements and nystagmus occurred more frequently in cows (p < .05). No difference between bulls and cows was determined in the occurrence of a response to painful stimuli or attempts to regain normal posture. No dependency was determined between the frequency of the occurrence of a reflex/reaction and the distance of the stun shot from the ideal point on the skull for any of the monitored signs. This study shows that the occurrence of reflexes/reactions following the stunning of cattle with a captive bolt is not only dependent on the position of the shot if placed within a 9 cm radius from the ideal point on the cattle skull.     

Brain and skull lesions resulting from use of percussive bolt, cervical dislocation by stretching, cervical dislocation by crushing and blunt trauma in turkeys

Three experiments were conducted to assess brain damage resulting from percussive bolt shooting and cervical dislocation by crushing (neck crushing) in turkey hens (mean [se] bodyweight 11.4 [0.1] kg); percussive bolt shooting and blunt trauma in turkey toms (13.1 [0.2] kg); and percussive bolt shooting, blunt trauma and cervical dislocation by stretching (neck stretching) in broiler turkeys (3.9 [0.3] kg). Brain and skull damage were assessed using macroscopic and microscopic evaluations and CT. Macroscopic subcutaneous haemorrhage was significantly greater with the percussive bolt in all three experiments (hens P=0.01, toms P=0.02, broilers P=0.0003), and skull fractures were more severe for toms (P<0.0001) and broilers (P=0.03) killed with the percussive bolt versus blunt trauma. In a subsample of turkeys, microscopic brain damage was present in all turkeys killed by percussive bolt shooting (five hens, 10 toms and four broilers) and blunt trauma (nine toms and three broilers), but only in one of four turkeys killed by neck crushing and one of four turkeys killed by neck stretching. Percussive bolt shooting and blunt trauma most likely caused death by directly disrupting brain function, whereas neck stretching and neck crushing probably resulted in death from cerebral hypoxia and ischaemia.     

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.     

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.     

Effect of electrical stunning on somatosensory evoked potentials in chickens

The spontaneous EEG and somatosensory evoked potentials (SEPs) were examined in chickens before and after electrical stunning using a waterbath stunner. Fifty-four per cent of the birds became epileptic and lost their SEPs, and 17% were non-epileptic and appeared to retain their SEPs. It was concluded that there was a reasonably close association between the presence of epileptiform activity in the EEG and the absence of SEPs following electrical stunning, but that the absence of SEPs could be preferred as an indicator of an effective stun on conceptual grounds.     

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.     

Investigation into the principal determinants of effective captive bolt stunning of sheep

In order to identify the physical component of captive bolt stunning responsible for abolishing visual evoked responses, experimental forms of captive bolt stunning were carried out on anaesthetised sheep. Supporting the captive bolt pistol away from the skull to permit limited penetration of the brain was found to be as effective as conventional shooting methods at abolishing visual evoked responses (responses were lost in all animals). Whereas, manual insertion of the bolt through a trephined hole or shooting through a trephined hole was significantly less effective (respectively, one of eight and four of eight animals lost responses). It is concluded that the impact of the bolt with the cranium is the principal determinant of effective stunning, rather than the penetration of the bolt into the brain tissues.     

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-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.     

Identifying Process Variables for a Low Atmospheric Pressure Stunning-Killing System

Current systems for preslaughter gas stunning and killing of broilers use process gases such as CO₂, N₂, Ar, or a mixture of these gases with air or O₂. These systems, known as controlled-atmosphere stunning-killing systems, work by displacing O₂, ultimately to induce hypoxia in the bird, leading to unconsciousness and death. In this study, mechanical removal of O₂ by rapidly reducing air pressure was investigated as an alternative to controlled-atmosphere stunning-killing systems. Low atmospheric pressure systems could offer advantages in worker safety and operational gas cost because they operate solely with atmospheric air. This study comprised 2 experiments, one to define the initial range of effective pressures, and the second to determine a recommended process pressure. In experiment 1, 48 female broilers, aged 63 d, were subjected to 6 different pressure treatments, ranging from 70.9 to 17.8 kPa. In experiment 2, 56 male broilers, aged 60 d, were subjected to 7 different pressure treatments, ranging from 35.3 to 17.8 kPa. Birds were individually placed in an airtight vessel and exposed to a pressure treatment for 2 min after the final pressure was attained. Results from experiment 1 showed that the effective range of pressure was between 29.5 and 17.8 kPa, with only 25% of the birds exposed to 29.5 kPa surviving and none of the birds exposed to 17.8 kPa surviving. Experiment 2 used a finer resolution of pressure increments, and the estimated pressure level lethal for 99.99% of the birds was determined to be 19.4 kPa.     

Concussive methods of pre-slaughter stunning in sheep: effects of captive bolt stunning in the poll position on brain function

The effectiveness of captive bolt stunning in the poll position was evaluated in eight anaesthetised sheep. Brain function following shooting was assessed using cortical visual evoked responses (VERs). Immediately following shooting, VERs were abolished in all sheep. However, in five of the sheep, VERs gradually recovered; responses became evident in these animals in a mean (+/- SE) time of 50 +/- 16.7 seconds. These results suggest that captive bolt shooting in the poll position can be associated with rapid recovery of brain function. Because such recovery could be associated with return of sensibility, shooting in the poll position should only be used when essential (ie, in horned animals) and then always followed promptly by sticking.     

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.     

The effects of CO2 gas stunning on meat quality of cattle compared with captive bolt stunning

The aim of this study is to assess the effect of CO₂ gas stunning which has not been conducted until now in comparison with captive bolt stunning on the meat quality of cattle. A total of 40 steers were slaughtered following two stunning processes: CO₂ gas stunning (n=20), exposure at 70% CO₂ gas atmosphere for 140 sec; and captive bolt stunning (CBS, n=20). The slaughtered steers were classified into Group A (620–710 kg) and Group B (720–790 kg) by their live weight. CO₂ gas stunning decreases pH value (p<0.05) but increases lightness (p<0.001) and sarcomere length (p<0.001 and p<0.01 for Group A and Group B, respectively) in all live weight groups. Drip loss was increased with CO₂ gas stunning in Group A (620–710 kg of live weight) (p<0.05), whereas WBSF was decreased with CO₂ gas stunning in Group B (720–790 kg of live weight) (p<0.001). Therefore, CO₂ gas stunning negatively affects muscle pH and water-holding capacity in steers but CO₂ gas stunning can improve the tenderness and lightness compared with captive bolt stunning in cattle.     

Review of the production of ostrich meat

Ostrich meat was originally considered to be a by-product of the leather industry. Ostrich farming focused on the production of good quality hides and was mainly based on experience. Since a few years there has been a move from hide production to meat production; however, little is known about ostrich meat production which has consequences for legislation. There is insufficient knowledge about the factors influencing muscle growth. The strong growth of ostrich meat production in the EU member states should be discussed because the climatic conditions are not optimal and the price of the meat may remain high compared to meat of broilers, pigs, and cattle. Information programmes have to be set up for all members in the production chain. The present method for stunning of ostriches has to be changed in most slaughterhouses. In this study the effects of electrical and mechanical stunning on unconsciousness, duration of unconsciousness, behaviour, and meat quality parameters were examined. At least 500 mA is needed to stun ostriches effectively, and they can be killed using a short-stick interval or a long stunning duration. A modified captive needle pistol, using air pressure, is an alternative to electrical head-only stunning.     

Reflexes and loss of sensibility following head-to-back electrical stunning in sheep

The effects of head-to-back electrical stunning on the incidence of post-stunning reflex activity and cortical evoked responses were investigated in sheep. The stuns were effective in terms of inducing epileptiform activity and they resulted in cardiac fibrillation which ensured that there was no recovery of consciousness. Even though the corneal reflex and respiratory gasps were present, in 10 out of 12 sheep there were no concomitant visual and somatosensory evoked responses following a stun. In the remaining two, the responses were rudimentary and it would be unwise to conclude that the animals were conscious. It is suggested that brain stem reflexes following this stunning method should not be relied on as indices of recovery. The results support the view that an electrical stunning method which induces cardiac fibrillation results in improved animal welfare.