Article

Welfare Implications of the Gas Stunning of Pigs 2. Stress of Induction of Anaesthesia

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Abstract

The severity of respiratory distress occurring prior to loss of posture during exposure to: 20, 30, 40, 50, 60, 70, 80 or 90 per cent carbon dioxide in air; 2 or 5 per cent residual oxygen in argon; 30 per cent carbon dioxide in argon with either 2 or 5 per cent residual oxygen; or 40 per cent carbon dioxide in argon with either 2 or 5 per cent residual oxygen, was subjectively determined in pigs from their behaviour. The results indicated that exposure to 2 per cent oxygen in argon (anoxia) induced minimal respiratory distress, 30 per cent carbon dioxide in argon with 2 per cent residual oxygen induced a moderate distress and exposure to all the concentrations of carbon dioxide in air induced severe respiratory distress in the pigs. From the animal welfare point of view, using 2 per cent oxygen in argon (anoxia) appears to be the optimum choice for gas stunning pigs. Secondly, a mixture of 30 per cent carbon dioxide in argon with 2 per cent residual oxygen is preferred to 90 per cent carbon dioxide in air.

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... The acidification of the brain cells results in a depression of brain activity that causes loss of consciousness or when prolonged death (6). Loss of consciousness is not immediate upon exposure to high CO2 levels, but depends on the CO2 concentration used and the speed at which animals are immersed into the highest concentration of CO2 at bottom of the well (7,8). Time to loss of posture, as the first indicator of the onset of unconsciousness, was reported at 25, 17, 22, and 15 s after immersion into 60, 70, 80, and 90% CO2, respectively (7). ...
... Loss of consciousness is not immediate upon exposure to high CO2 levels, but depends on the CO2 concentration used and the speed at which animals are immersed into the highest concentration of CO2 at bottom of the well (7,8). Time to loss of posture, as the first indicator of the onset of unconsciousness, was reported at 25, 17, 22, and 15 s after immersion into 60, 70, 80, and 90% CO2, respectively (7). Studies that examine brain activity, presented in an electroencephalogram (EEG), reported loss of consciousness 14-60 s after initial exposure to 80-90% CO2 (9, 10). ...
... Pigs do not need to be individually restrained and can be stunned in groups during CO2 stunning, which are considered to be advantages in terms of animal welfare in comparison to other stunning methods (10,11). Before pigs lose consciousness, however, behavior, including excitement, retreat and escape attempts, and respiratory changes (gasping), has been observed (3,7,12,13). Carbon dioxide itself causes irritation of nasal mucosal membranes and is a strong respiratory stimulator that induces a sense of breathlessness prior to loss of consciousness in humans (14,15). ...
Article
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Exposure to CO2 at high concentration is a much debated stunning method in pigs. Pigs respond aversively to high concentrations of CO2 and there is uncertainty about what behaviors occur before and after loss of consciousness. The aim was to assess timing of unconsciousness in pigs during exposure to high concentrations of CO2 based upon changes in EEG activity and the relation with the behaviors sniffing, retreat- and escape attempts, lateral head movements, jumping, muscular contractions, loss of posture, and gasping. Pigs (108 ± 9 kg) were randomly assigned to 80% CO2 (80C, n=24) or 95% CO2 (95C, n=24). The time at which the gondola started descending into the well pre-filled with 80C or 95C was marked as T=0. The CO2 exposure lasted 346s after which the corneal reflex and breathing were assessed for one minute. Visual assessment of changes in the amplitude and frequency of EEG traces after T=0 was used to determine loss of consciousness. Time to loss of consciousness was longer in 80C pigs (47 ± 6s) than in 95C pigs (33 ± 7s). Time to an iso-electric EEG was similar in 80C pigs (75 ± 23s) and 95C pigs (64 ± 32s). When pigs descended into the well, the earlier entry of 95C pigs into high CO2 atmosphere rather than the concentration of CO2 by itself affected the latency of behavioural responses and decreasing brain activity. During exposure to the gas, 80C and 95C pigs exhibited sniffing, retreat attempts, lateral head movements, jumping and gasping before loss of consciousness. 95C pigs exhibited all these behaviors on average earlier than 80C pigs after T=0. But the interval between onset of these behaviors and loss of consciousness and the duration of these behaviors, except gasping, was similar for both treatments. Loss of posture was on average observed in both groups 10s before EEG-based loss of consciousness. Furthermore, 88% of 80C pigs and 94% of 95C pigs demonstrated muscular contractions before loss of consciousness. The findings provide little reason to conclude on a behavioral basis that these atmospheres are greatly different in their impact on pig welfare.
... Respiratory distress is shown by gasping or intense breathing (characterised by a very deep breath through a gaping-open mouth, indicative of breathlessness (Raj and Gregory, 1996;EFSA, 2004). Gasping will start before loss of consciousness and will persist for a certain time afterwards. ...
... Effective head-only electrical stunning induces loss of consciousness that is characterised by immediate collapse of the animal and tonic immobility during exposure to the stunning current. Immediately after exposure to the current, pigs show tonic seizure followed by clonic seizures, (Raj and Gregory, 1996;EFSA, 2004) Hyperventilation Excessive rate and depth of breathing (Raj and Gregory, 1996) Head shaking Rapid shaking of the head, most times accompanied by stretching and/or withdrawal movements of the head (EFSA, 2004) indicative of generalised epilepsy. Typically, during the tonic phase pigs are in a state of tetanus and stretch out their fore-and hind-legs, breathing is absent and the eyeballs are fixed or rotated into the socket. ...
... Effective head-only electrical stunning induces loss of consciousness that is characterised by immediate collapse of the animal and tonic immobility during exposure to the stunning current. Immediately after exposure to the current, pigs show tonic seizure followed by clonic seizures, (Raj and Gregory, 1996;EFSA, 2004) Hyperventilation Excessive rate and depth of breathing (Raj and Gregory, 1996) Head shaking Rapid shaking of the head, most times accompanied by stretching and/or withdrawal movements of the head (EFSA, 2004) indicative of generalised epilepsy. Typically, during the tonic phase pigs are in a state of tetanus and stretch out their fore-and hind-legs, breathing is absent and the eyeballs are fixed or rotated into the socket. ...
Article
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Abstract The killing of pigs for human consumption (slaughtering) can take place in a slaughterhouse or on farm. The processes of slaughtering that were assessed for welfare, from the arrival of pigs until their death, were grouped into three main phases: pre‐stunning (including arrival, unloading from the truck, lairage, handling and moving of pigs); stunning (including restraint); and bleeding. Stunning methods were grouped into three categories: electrical, controlled atmosphere and mechanical. Twelve welfare consequences the pigs can be exposed to during slaughter were identified: heat stress, cold stress, fatigue, prolonged thirst, prolonged hunger, impeded movement, restriction of movements, resting problem, negative social behaviour, pain, fear and respiratory distress. Welfare consequences and relevant animal‐based measures were described. In total, 30 welfare hazards that could occur during slaughter were identified and characterised, most of them related to stunning and bleeding. Staff were identified as the origin of 29 hazards, which were attributed to the lack of appropriate skill sets needed to perform tasks or to fatigue. Corrective and preventive measures for these hazards were assessed: measures to correct hazards were identified, and management was shown to have a crucial role in prevention. Outcome tables linking hazards, welfare consequences, animal‐based measures, origins and preventive and corrective measures were developed for each process. Mitigation measures to minimise welfare consequences are proposed.
... The greater the concentration of CO 2 in the system interior, more rapid is the induction to unconsciousness. 103 The advantage of this system is that it does not require animal restraint and allows group stunning, decreasing handling and gas behavioural reactivity. 95 This is a safe system for operators and reduces the incidence of PSE meat, and ham and loin bruising. ...
... 95 This is a safe system for operators and reduces the incidence of PSE meat, and ham and loin bruising. 104 However, this method has some disadvantages, because there is no immediate unconsciousness and pigs show aversion signs during exposition, 103 besides causing hyperventilation and respiratory failure. 105 Currently, alternatives are being considered to reduce aversion to CO 2 , especially combination of this with other gases. ...
... Cuanto mayor es la concentración de CO 2 en el interior del sistema, más rápida es la inducción a la inconsciencia. 103 La ventaja de este sistema es que no requiere la sujeción de los animales y permite el aturdimiento en grupo, reduciendo el manejo y la reactividad conductual al gas. 95 Este sistema es seguro para los operarios y reduce la incidencia de carne PSE, equimosis en los jamones y lomo. ...
Article
Logistics and transport are of strategic importance in animal welfare, the quality of the product and production efficiency. In essence, pre-slaughter logistics comprises all of the stages involved in transporting and handling animals on their journey from the farm to the slaughterhouse. This review gives an up-to-date analysis of pre-slaughter transport and logistics as a whole. Taking into account the current trends towards increased transport times, logistics of scale and mixed modes of transport, there is a need to develop systems of evaluation and decision-making that provide tools and protocols capable of minimizing the biological cost associated with animals adapting to pre-slaughter logistics. Possibly, in the past, the impact of pre-slaughter stress has been underestimated, but there is evidence that would suggest the importance of investing in operational changes at the present time.
... 258 In contrast to other species, a large proportion of chickens and turkeys will enter a chamber containing moderate concentrations of CO 2 (60%) to gain access to food or social contact. 197,202,250 Following incapacitation and prior to loss of consciousness, birds in these studies show behaviors such as open-beak breathing and head-shaking; these behaviors, however, may not be associated with distress because birds do not withdraw from CO 2 when these behaviors occur. 203 Thus, it appears that birds are more willing than rodents and mink to tolerate CO 2 at concentrations that are sufficient to induce loss of posture, and that loss of consciousness follows shortly afterwards. ...
... 261 Given a choice, Duroc and Large White pigs will tolerate 30% CO 2 to gain access to a food reward, but will forgo the reward to avoid exposure to 90% CO 2 , even after a 24-hour period of food deprivation. 206,250 A shock with an electric prod, however, is more aversive to Landrace X Large White pigs than inhaling 60% or 90% CO 2 , with pigs inhaling 60% CO 2 willing to reenter the crate containing CO 2 . 251 Until further research is conducted, one can conclude that use of CO 2 may be humane for certain genetic lines of pigs and stressful for others. ...
... For cats, inhalation of 60% CO 2 results in loss of consciousness within 45 seconds, and respiratory arrest within 5 minutes. 264 For pigs, exposure to 60% to 90% CO 2 causes unconsciousness in 14 to 30 seconds, [210][211][212]250 with unconsciousness occurring prior to onset of signs of excitation. 210,214 Euthanasia via exposure to CO 2 has been described for individual birds and small groups, 265 and its application to euthanasia of chickens, turkeys, and ducks has been studied extensively, resulting in information about times to collapse, unconsciousness and death, loss of somatosensory evoked potentials, and changes in EEG. ...
... These symptoms are: forced breathing, swaying or wagging, loss of posture, vocalisation and recumbency after a certain time. Reactions like retreat movements, vigorous head shaking or flight reactions, which have been considered as signs of aversion by Dodman (1977) and Raj and Gregory (1996), did not appear in this study. This might be either due to the chosen atmosphere (max. ...
... 30% CO 2 in N 2 and less than 2% O 2 ) and/ or a slower increase of CO 2 and decrease of O 2 . In comparable studies of Dalmau et al. (2010); Raj and Gregory (1996) pigs are lowered into a pit filled with premixed gas atmospheres. In these studies it was also found, that lowering the pigs in a cradle in atmospheric air by itself was able to cause excitement and fear reactions. ...
... In a study by Raj and Gregory (1996) with pigs (15-30 kg) placed in 30% CO 2 in argon with less than 2% O 2 , the mean time period between start of forced breathing and loss of posture was 18s. The shorter interval compared to the present study might be caused by a faster exposition into the stunning atmosphere. ...
Research
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Summary Outbreaks of notifiable diseases such as classical swine fever or hazards like dioxin contamination of animal feedstuffs require the on-farm culling of large groups of pigs. There is growing concern about the currently applied method of stunning and killing using manual electrocution and it is searched for applicable alternative methods to stun and kill pigs on-farm. This paper looks into the possibility of using a container system for gassing pigs with a gas mixture of N2 and CO2, a method developed by the Total Culling Concept (TCC) Group. This container gassing system was investigated in relation to aspects of animal welfare, operation safety and reliability of function. A total of 55 pigs (including piglets of one week of age up to adult sows) were used of which 23 animals were equipped with data loggers to record brain- (EEG) and heart (ECG) activity during gas injection. The complete study was recorded and behavioural analyses could be performed afterwards. Gas injection lead 150 to 180s after start of gas injection to an atmosphere consisting of 28% CO2, 71% N2 and 1% residual O2. Based on the behavioural observations from all pigs, the typical sequence of reactions was: intensified breathing, wobbling and falling down after 79-204s and a last movement was an isolated gasp (309-564s). No fleeing behaviour was observed prior to loss of posture. Vocalisation occurred around loss of posture or shortly thereafter. At the moment of swaying or loss of posture the pigs attempted to maintain balance. On average, pigs fell 145 seconds after gas injection at which also a suppressed EEG was observed. Shortly after the onset of CO2 injection the heartbeat declined rapidly to at least 50% of baseline value (175 bpm). As heartbeat declined, it became irregular and eventually lead to a cardiac arrest in all pigs. If culling cannot be avoided, the highest possible animal welfare standard is required. In this case, exposure to the gas mixture was not considered to be aversive to the pigs. There have been defined potential periods of stress but they were considered to be brief. Therefore, when large groups of animals have to be culled in an emergency, the gassing method tested in this project provides an acceptable option.
... In humans, inhalation of high concentrations of CO 2 causes irritation of the respiratory tract and a sensation of breathlessness, and in pigs CO 2 induces severe respiratory distress causing hyperventilation and breathlessness during the induction phase prior to loss of consciousness (Gregory et al., 1990). Before loss of posture, pigs show vigorous head shaking (EFSA, 2004), a very deep breath through the wide-open mouth, which is indicative of the onset of breathlessness, and escape attempts (Raj and Gregory, 1996), all of them considered to be signs of aversion to the gas. In rabbits, Llonch et al. (2012a) indicated that general activity, nasal movements and head shaking could also be indicative of aversion in this species. ...
... During exposure to the atmospheric air and the gas treatments, the following variables were measured: 1. Activity, considering the number of lines crossed by animals (defined as a line crossed when the 2 forelimbs completely exceeded one of the marked lines on the floor of the crate); 2. Vocalisations (when the animal screamed); 3. Nasal discomfort (when animals began to touch the nose with the forelimbs and shook the head from side to side), and 4. Loss of posture (when the animal touched the floor of the crate with the abdomen or side with outstretched limbs). This last measure has been used in other species as an indicator of the onset of unconsciousness, to be able to anticipate the end of the aversion period (Raj and Gregory, 1996). Another parameter assessed was the presence of muscular jerks, defined as repeated muscular movement of the whole body, where it is not clear whether it occurs in conscious or unconscious animals (Rodriguez et al., 2008). ...
... One difference between the study of Llonch et al. (2012a) and the present study is that in the former the animals were subjected to air and gas on different days, whereas in the present study both exposures (air and gas) were tested the same day. Figure 2 shows the percentage of animals with nasal discomfort and vocalisations, considered to be 2 signs of aversion (EFSA, 2004), and loss of posture (considered the first sign of onset of unconsciousness; Raj and Gregory, 1996). None of these signs was observed when rabbits were subjected to atmospheric air. ...
Article
An investigation was performed to determine whether high concentrations of carbon dioxide (CO2) at 70-98% in atmospheric air are a suitable alternative for stunning rabbits compared to conventional approaches such as electronarcosis. Aversion to the gas and efficacy in causing prolonged unconsciousness and death were studied in a total of 480 rabbits by means of behavioural parameters, physiological indicators (presence of rhythmic breathing and corneal reflex) and electroencephalography (EEG, brain function). The use of any of the 4 studied concentrations of the gas caused more nasal discomfort and vocalisations than the use of atmospheric air (P<0.001). EEG activity confirmed that loss of posture is a good indicator of the onset of unconsciousness in rabbits exposed to CO2, occurring earlier (P<0.05) at 90 and 98% than at 70 and 80%. Rabbits showed signs of aversion for 15 s before the onset of unconsciousness, which occurred around 30 s after the beginning of the exposure to the gas, similar to species such as swine in which high concentrations of CO2 are also used for stunning. CO2 at 80 to 98% is suggested as a reasonable concentration range to induce a long state of unconsciousness and death in rabbits, while 70% CO2 is not recommended because it requires too long duration of exposure (more than 360 s) to ensure effectiveness. Despite the advantages in terms of pre-stun handling and irreversibility, CO2 is not free of animal welfare concerns. In consequence, a debate is necessary to ascertain if CO2 can be considered a suitable alternative to stun rabbits, considering the advantages and drawbacks cited, quantified in the present study as 15 s of aversion (nasal discomfort and vocalisations) before losing posture.
... The acidification of the brain cells induces a depression of brain activity that causes loss of consciousness and ultimately death (Martoft et al., 2002). Loss of consciousness is not immediate upon exposure to high CO 2 levels, but depends on the CO 2 concentration used and the speed at which animals are immersed into the highest concentration of CO 2 at the bottom of the well (Troeger, 1991, Raj andGregory, 1996). Time to unconsciousness has been reported 14-60 s after initial exposure to 80-90% CO 2 (Raj and Gregory, 1996;EFSA, 2004;Rodriguez et al., 2008). ...
... Loss of consciousness is not immediate upon exposure to high CO 2 levels, but depends on the CO 2 concentration used and the speed at which animals are immersed into the highest concentration of CO 2 at the bottom of the well (Troeger, 1991, Raj andGregory, 1996). Time to unconsciousness has been reported 14-60 s after initial exposure to 80-90% CO 2 (Raj and Gregory, 1996;EFSA, 2004;Rodriguez et al., 2008). The duration of unconsciousness depends on the concentration of CO 2 used and the exposure time to the gas (EFSA, 2004). ...
... Loss of posture, the inability of the animal to remain in an initial standing or sitting position, is considered a valuable indicator as it is often the first sign to be lost after successful stunning and indicates that the cerebral cortex is no longer able to control posture (Raj et al., 1992;Raj and Gregory, 1996;Llonch et al., 2013). Both mechanical and electrical stunning should lead to immediate collapse (AVMA, 2013). ...
... However, prior to this there is the potential for animals to experience severe breathlessness due to hypercapnia [18][19][20], as well as pain due to the formation of carbonic acid in the nasal and respiratory mucosa [21,22]. Moreover, behavioural and/or physiological signs of distress in response to CO 2 inhalation have been reported in rats [15], broiler chickens [10,23] and pigs [24,25]. ...
... Finishing pigs readily entered a chamber containing 90% Ar for a food reward but avoided entering a chamber containing 90% CO 2 [27]. Furthermore, exposure to 2% oxygen in Ar induced minimal respiratory stress compared to 90% CO 2 in pigs [24]. Therefore, Ar maybe preferable to 100% CO 2 as a method of euthanasia for pigs based on indicators of animal welfare. ...
... Pigs exposed to 2% oxygen in Ar took twice as long to lose consciousness (latency to loss of posture) as pigs exposed to 90% CO 2 [27], potentially reducing the practicality of using Ar alone as a method of on-farm euthanasia for piglets. However, mixing Ar with CO 2 could potentially reduce the time to loss of posture in pigs and cause less stress than exposing pigs to 90% CO 2 [24]. A 50:50 mixture of Ar and CO 2 did not improve the welfare of neonatal piglets during gas exposure compared with 100% CO 2 [12]. ...
Article
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The aim of this research was to evaluate the welfare of pre-weaned piglets euthanised using three different gas treatments: 100% carbon dioxide (CO₂), 100% argon (Ar) or a mixture of 60% Ar/40% carbon dioxide (Ar/CO₂). Two studies (n = 5 piglets/treatment/study) were conducted: (1) behavioural and physiological data were collected from conscious piglets during exposure to test gases via immersion in a pre-filled chamber and (2) electrophysiological data were collected from lightly anaesthetised, intubated and mechanically ventilated piglets exposed to the same test gases. Based on the duration of escape attempts and laboured breathing, piglets exposed to 100% CO₂ experienced more stress than piglets exposed to 100% Ar prior to loss of consciousness, but there appeared to be no advantage of mixing Ar with CO₂ on indices of animal welfare. However, spectral analysis of the electroencephalogram revealed no changes consistent with nociception during exposure to any of the three gas treatments. Based on the behavioural response to gas exposure, all gases tested caused signs of stress prior to piglets losing consciousness and hence alternative methods of euthanasia need to be evaluated.
... Par exemple, l'exposition de rats à des concentrations de 30 et de 100% de CO 2 induisent une perte de conscience après 150 et 54 s d'inhalation respectivement (Sharp et al., 2006). Chez le porc, l'exposition à 20 ou 30% de CO 2 pendant une minute ne provoque pas de perte de la posture debout (Raj et Gregory, 1996). Les délais de la perte de posture étaient de 44, 20, 22 et 16 s pour des expositions à 40, 50, 60, et 70% de CO 2 dans de l'air (Raj et Gregory, 1996). ...
... Chez le porc, l'exposition à 20 ou 30% de CO 2 pendant une minute ne provoque pas de perte de la posture debout (Raj et Gregory, 1996). Les délais de la perte de posture étaient de 44, 20, 22 et 16 s pour des expositions à 40, 50, 60, et 70% de CO 2 dans de l'air (Raj et Gregory, 1996). ...
... Les concentrations de CO 2 plus élevées induisent plus rapidement l'inconscience. En revanche, elles provoquent plus de réactions comportementales associées à des situations d'aversion, comme des troubles respiratoires, plus intenses (Dodman, 1977 ;Raj et Gregory, 1996 ;Gerritzen et al., 2004 ;Conlee et al., 2005 ;Sandilands et al., 2011). ...
Article
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Cette revue (qui sera suivie par un second article) présente les mécanismes neurobiologiques impliqués lors de l’étourdissement et la mise à mort des animaux en abattoir. Lorsqu’un étourdissement précède la saignée, les mécanismes impliqués dans la perte de conscience varient selon les techniques utilisées : étourdissement mécanique, électrique ou gazeux. La saignée directe (sans étourdissement) induit également une perte de conscience avant de provoquer la mort. La perte de conscience peut être liée à différents mécanismes, tels que l’anoxie ou l’ischémie cérébrale ou la dépolarisation, l’acidification et/ou la destruction des neurones. Ces effets peuvent être produits à l’aide d’ondes de choc, de champs électriques, de réduction ou d’arrêt de la circulation sanguine cérébrale, d’une surcharge de CO 2 et/ou d’un manque d’O 2 dans l’air inspiré, ou de la destruction mécanique de neurones. Les structures cérébrales visées sont la formation réticulée, le système réticulo-activateur ascendant ou encore les hémisphères cérébraux de manière globale. Certaines techniques, lorsqu ’elles sont bien utilisées, permettent une perte de conscience immédiate ; pour d’autres, la pert e de conscience est progressive.
... However, the high concentration of CO2 gas has been shown to induce aversion in pigs prior to loss of consciousness [2,3,5]. CO2 gas at high concentration is acidic when inhaled and can cause painful irritation to nasal mucosa [6] and has been shown to cause air hunger and breathlessness, which may be a sign of severe distress [3]. The European Food Safety Authority (EFSA) [7] has defined animal-based measures for pigs related to pain, fear and respiratory distress during exposure to high concentrations of CO2 to be associated with excitation behaviour, retreat, escape attempts, and gasping. ...
... For the pigs in the Nitrogen foam treatment, the time from the start of the foam production until loss of posture (LOP) was recorded. The time to loss of posture, defined by the inability of the pig to remain in a standing position, was considered the first indicator of the onset of unconsciousness [6]. Convulsions (muscular excitation) were described qualitatively by intensity and type of convulsions, e.g., kicking, gagging, and the time until last observed muscular contraction was registered. ...
... The percentages of pigs showing escape and exploring behaviours, lying and vocalisation (grunts and screams) at least once during each 10 s interval (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12) for each treatment are shown in Figures 5-7. Movement (measured as mean times the pig crossed the tape marking quadrant lines on the floor during an interval) for each treatment is shown in Figure 8. ...
Article
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Nitrogen gas (N 2) delivered in high expansion foam in a closed container could be a feasible method for humanely stunning pigs. This study aimed to evaluate potential aversion in pigs to the N 2 foam method and its effect on stun quality. Furthermore, the study aimed to assess potential aversion to the foam itself. Sixty pigs (27.8 ± 4.4 kg) were divided into three treatments and were exposed to either N 2-filled foam, air-filled foam, or no foam air. The N 2 foam was effective at purging the air from the container and quickly created stable anoxic conditions. The pigs did not show any strong aversive behaviours when exposed to foam. However, they seemed to avoid putting their heads and snouts into the foam when foam levels became high. Escape attempts through the lid also increased when the foam started covering their heads. The mean time to loss of posture was 57.9 s. Based on the results, stunning with the N 2 foam technique could be a viable alternative to high concentration CO 2 stunning and potentially lead to improved animal welfare at slaughter.
... The selection of a depopulation method varies based on the specific purpose of the method, age and number of pigs, available personnel, and availability of equipment and resources. The use of inhalable gaseous formulations, mainly carbon dioxide (CO 2 ), appears to be the most studied depopulation method in the swine industry [3,13,[17][18][19][20][21][22][23][24][25][26][27]. This method allows for multiple pigs to be euthanized at once, reduces the need for individual pig handling and instrument application, and is effective across all pig age categories. ...
... Twelve experimental studies assessed different concentrations of gaseous carbon dioxide (CO 2 ), nitrogen (N 2 ), argon, and combinations in reducing respiratory distress in young and adult pigs during euthanasia or depopulation [13,[17][18][19][20][21][22][23]28,32,33]. Three studies assessed the effectiveness of a non-penetrating captive bolt for euthanasia of newborn piglets [34][35][36]. ...
... Four studies [13,17,23,28] assessed the efficacy of various concentrations of CO 2 for euthanasia of both individual animals and groups of up to 658 pigs. The remaining eight studies [18][19][20][21][22]32,33] examined the efficacy of N 2 only or CO 2 for euthanasia in comparison to other methods, including N 2, CO 2 mixture with argon, CO 2 mixture with nitrogen, and prior exposure to nitrous oxide (N 2 O) followed by CO 2 and electrocution. Approximately half of the studies were on young pre-weaned piglets while the rest were on adult pigs. ...
Article
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Swine mass depopulation refers to the destruction of large numbers of pigs and may include not only animals affected with a disease but also healthy pigs in a facility or surrounding areas. Emerging applications of mass depopulation include reducing welfare issues associated with slaughter delays, which was observed in the United States in 2020 as a result of the Coronavirus disease (COVID-19) pandemic. The objectives of this review were to summarize the available literature on swine depopulation methods and to highlight critical gaps in knowledge. Peer-reviewed articles were identified through a systematic search in electronic databases including Web of Science, MEDLINE, and PubMed. A total of 68 publications were assessed. Gaseous carbon dioxide inhalation was the most commonly reported depopulation method for both small- and large-scale trials. Measurements of consciousness state, which serves to assess suffering and humaneness, appeared to be lacking in a high proportion of the studies. None of the published studies demonstrated an ideally reliable and safe way to induce rapid unconsciousness in large groups of pigs. Development of rapid mass depopulation methods applicable to large groups of pigs is necessary to provide industry partners with suitable and low-cost emergency preparedness procedures while adhering to personnel safety and animal welfare standards. Lastly, there is an urgent need to standardize comprehensive reporting guidelines for depopulation studies.
... Velarde [2] and Raj and Gregory [7] found that hypercapnic stunning leads to an elapsed time period where loss of consciousness occurs. Raj and Gregory [8], Velarde et al. [6], and Verhoeven et al. [9] all found that during this time period, induction of unconsciousness is often considered to be aversive and stressful, indicated by a series of observed behaviors. Verhoeven [9] found that sniffing, retreat attempts, lateral head movements, jumping, and gasping all occurred before loss of consciousness, which was confirmed via EEG latency, indicating ceased brain activity (when pigs were stunned in 80 or 95% CO 2 atmospheres). ...
... The first sequence of behaviors shown during gas exposure in both stunning methods were retreat and escape attempts, both considered signs of aversion [8,24]. The first appearance of aversive behavior could be due to the inhalation of the gas mixture. ...
... The time to lose posture is considered the first behavioral indicator of the onset of unconsciousness [8]. In our study, loss of posture was the time when animals showed the inability to stand in an upright position, but it did not necessarily mean that they started to lay, as in numerous occasions pigs struggled to maintain their position. ...
Article
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This study assessed aversion, stunning effectiveness, and product quality of nitrogen and carbon dioxide (CO2) mixtures used for stunning pigs. A total of 1852 slaughter pigs divided into two similar batches was assessed during routine slaughter in a Swedish commercial abattoir using either hypercapnic-hypoxia (20% CO2 and less than 2% O2; 20C2O) or hypercapnia (90% CO2; 90C) gas mixtures. Behavioral indicators of aversion and discomfort were recorded. After exposure, the stunning quality was assessed through brainstem reflexes. After slaughter, the pH and electric conductivity of carcasses were assessed to estimate the incidence of pale, soft, and exudative (PSE) pork, and the presence of ecchymosis were inspected. Compared to 90C, pigs exposed to 20C2O showed a later (p < 0.05) onset of behaviors indicative of aversion, and a lower (p < 0.01) incidence of breathlessness. However, unconsciousness (i.e., losing posture) appeared earlier (p < 0.01) in 90C compared to 20C2O. In 90C, all (100%) pigs were adequately stunned, whereas in 20C2O a 7.4% of pigs showed signs of poor stunning, especially when oxygen concentrations were >2% (p < 0.001). The percentage of PSE carcasses was higher (p < 0.01) in 20C2O than 90C. In conclusion, compared to 90C, 20C2O reduced aversion and discomfort but showed lower stun effectiveness, especially when O2 was above 2%, and a slightly poorer pork quality.
... Therefore, we consider heavy breathing and open-mouth breathing to be distressful behaviors, which are associated with compromised welfare [5,13]. Open-mouth breathing occurs just before the loss of posture when pigs were euthanized with CO 2 [14,19,20]. The latency to heavy breathing and open-mouth breathing started earlier in pigs exposed to CO 2 compared to N 2 O. Similarly, pigs exposed to CO 2 experienced this respiratory distress (HB and OMB) for a longer duration of time than pigs exposed to Ar [20]. ...
... Open-mouth breathing occurs just before the loss of posture when pigs were euthanized with CO 2 [14,19,20]. The latency to heavy breathing and open-mouth breathing started earlier in pigs exposed to CO 2 compared to N 2 O. Similarly, pigs exposed to CO 2 experienced this respiratory distress (HB and OMB) for a longer duration of time than pigs exposed to Ar [20]. In our study, we had similar results in terms of latency to heavy breathing between pigs of CO 2 and CO 2 B treatments; pigs in CO 2 had a shorter latency to respiratory distress compared to pigs in N 2 O. ...
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The swine industry is often forced to euthanize pigs in the first few weeks of life due to injuries, hernias, or unthriftiness. The majority of pigs are euthanized using carbon dioxide (CO2) gas asphyxiation but concerns as to the humaneness of CO2 are increasing. This study compared the euthanasia of weaned pigs using N2O (N2O; n = 9) or CO2 (n = 9), at 50% and 25% min−1 exchange rate, respectively. In addition, we administered an analgesic prior to euthanasia with CO2 (CO2B) exposure as a third treatment (n = 9) to elucidate behaviors indicative of pain. Pigs in the CO2 and N2O treatments lost posture at similar times (latency of 145.0 ± 17.3 and 162.6 ± 7.0 s respectively, p > 0.10), while the CO2B treatment pigs lost posture the soonest (101.2 ± 4.7 s, p < 0.01). The pigs in the CO2B treatment made more escape attempts than the CO2 or N2O pigs (16.4 ± 4.2, 4.7 ± 1.6, 0.3 ± 0.2, respectively; p < 0.0004). However, pigs in N2O squealed more often than either the CO2 or CO2B pigs (9.0 ± 1.6, 2.8 ± 1.2, 1.3 ± 0.6, respectively, p < 0.001). Given the similar time to loss of posture and shorter time displaying open mouth breathing, N2O may cause less stress to pigs; however, the greater number of squeals performed by these pigs suggests the opposite. It was not apparent that any behavior measured was indicative of pain. In conclusion, N2O applied at a 50%min−1 flow rate can be an alternative to CO2 for pig euthanasia.
... [3] detectaron altos niveles de lactato sanguíneo en cerdos aturdidos con diferentes métodos y mencionan que la lactoacidemia es un indicador de estrés resultado de la producción rápida de energía por un metabolismo anaerobio o una acidosis láctica por la acción de catecolaminas. Además, esto puede ser atribuido a una ruptura de las fibras de colágeno como resultado de un esfuerzo extremo o la rápida glucogenolisis debida al miedo o a la excitación [3, 13,21,32]. Así, la presión parcial de CO 2 baja (42,98 ± 0,98 mmHg) en comparación al grupo de referencia (58,16 ± 0,34 mmHg) que se presentó en este grupo de cerdos no aturdidos pudiera relacionarse con una acidosis respiratoria o metabólica caracterizada por un descenso en el pH y en la concentración de HCO 3 -acompañada por una hiperventilación compensadora que se traduce en la caída de pCO 2 indicando un proceso de estrés agudo, para restablecer las pérdidas en el balance ácido-base [15,22]. Por otro lado, se apreció una disminución de la concentración de oxígeno (26,72 ± 0,54) en los animales aturdidos eléctricamente (R 2 ). ...
... Estos cambios pudieran estar relacionados con la acidosis metabólica provocada por el metabolismo anaerobio y la correlación de la concentración de cationes (Na 2+ , K + , Ca ++ , Mg + ) lo que confirmaría que esta reacción del organismo es una respuesta al estrés y la agonía al momento del sacrificio [3,13]. Por otro lado, los cerdos aturdidos en cámaras de CO 2 (R 3 ) mostraron acidosis, hipercapnia, hiperglucemia, hiperpotasemia, y un elevado porcentaje de hematocrito, posiblemente debido a una acidosis respiratoria causada por una hipoventilación alveolar por el poco suministro de oxígeno (hipoxia) y el aumento en la concentración de CO 2 en la cámara (70% de concentración), lo que estimula la frecuencia respiratoria y puede conducir a insuficiencia respiratoria [21,30]. Además, en la cámara de CO 2 aumenta el metabolismo oxidativo anaerobio al haber poco oxigeno aumentando así los niveles de glucosa en el torrente sanguíneo y provocando aumento del flujo intracelular de iones K + por iones de hidrógeno, originando la acidosis metabólica [3]. ...
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The objective of this study was to evaluate the effect of stunning method on the physiometabolic profile in hogs during their killing. A total of 738 York-Landrace-Pietrain crossbreed pigs were used. The pigs were taken from three different establishments: Abattoir 1, pigs sacrificed without stunning (R1, n=140); Abattoir 2, pigs stunned using electrical stunning (R2, n=185); and Abattoir 3, hogs stunned in a CO2 chamber (R3, n=195). On the day prior to transport, blood samples (n=221) to determine basal values were taken. In the results, a significant increase in blood lactate levels (110.37 ± 2.72 mg / dL) was observed in the R1 group, as compared with the other 2 groups (P ≤ 0.01). On the other hand, the electrically stunned group of hogs (R2) showed reduced oxygen concentration (26.72 ± 0.54). Likewise, the blood pH of the R3 pigs decreased below 7.12 and the BCO2 increased (43.9 mmHg), when compared to R2 (P ≤ 0.01). In conclusion, the stunning methods used in Mexican abattoirs like electrical stunning and CO2 chamber, have negative consequences on animal welfare, due to stress at bleeding; nevertheless, the lack of a stunning method generates greater blood physiological imbalances and severe gas exchange alterations.
... Los efectos del CO 2 actúan por dos vías: la primera, causando irritación en la mucosa de las membranas nasales; y la segunda, como un agente que estimula fuertemente el centro respiratorio, provocando hiperventilación y sofocación antes perder la consciencia. Durante la inhalación, la 'pérdida de la postura' ha sido considerado como el primer indicador conductual justo antes de perder completamente la consciencia (Raj & Gregory 1996;Rodríguez et al., 2008). ...
... Aunado a ello, observé que la 'pérdida de la postura' aparece a partir de los 11 s (T 2 ) de haber iniciado el aturdimiento, lo que pudiera indicar que es aquí donde inicia la pérdida de la consciencia y el cerdo pierde la fuerza de sus cuatro extremidades, golpeando la pared o el piso de la juala de forma violenta; éste fenómeno puede ir acompañado de 'intentos para incorporarse' en algunos de los casos. La 'pérdida de la postura' ha sido reportado en otros estudios, donde los cerdos dejan de estar 'de pie' después de los 22 s de haber iniciado el aturdimiento (80% CO 2 ) (Raj & Gregory, 1996); años mas tarde, Gerritzen et al., (2008) mencionaron que cerdos adoptaron 'sentado' a los 16 ± 0.8 s de haber iniciado el aturdimiento con una combinación de gases (70% CO 2 +30% O 2 ), y eventualmente, perdieron la postura a partir de los 24±1 s. ...
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The objective of the present study was to evaluate the effect of different concentrations of CO2 on the stunning of pigs by measuring physiometabolic blood profiles and behavioral changes. In the first phase of the experiment, a total of 1336 pigs were stunned in a CO2 chamber (at 85%, 90% and 95% CO2) for approximately 90 s. The pigs exsanguinated during the first 60 s after leaving the chamber without recovering consciousness were classified as NRC, while those that were exsanguinated after more than 60 s and did recover consciousness were classified as SRC. Blood pH of the SRC pigs was below 7.08, while blood Ca2+ (>1.59 mmol/L), glucose (>159.79 mg/dL) and lactate (>103.52 mg/dL) levels all increased compared to the control group (P<0.05). In the second experimental phase, 336 pigs were videotaped during the first 30 s of the stunning process (at 86% CO2) and then classified in groups according to the time they were exposed to the gas, as follows: T1= 0-to-10 s, T2= 11-to-20 s, and T3= 21-to-30 s. Sixteen different behavioral traits were recorded and analyzed according to frequency percentage, prevalence, and duration (s). In T1, the most frequent and prevalent behaviors were sitting and standing (assimilation phase); in T2, pigs attempting to escape and stand up showed higher frequency and prevalence percentages (excitation phase); while in T3, the most common behavioral indicators were difficulty in maintaining posture and muscular contractions (anesthetic phase). Results show that the CO2 stunning method does not favor the welfare of pigs in the abattoir as shown by the alterations in their behavioral patterns which indicate aversion to the gas. All pigs exposed to CO2, regardless of concentration, presented changes in critical blood variables, and exposure to the gas also affected their acid-base balance, producing a process of acidosis, hyperglycemia, hyperlactatemia, hypercapnia and hyperpotasemia. This physiological disequilibrium was greater when the animals recovered consciousness seconds after leaving the stunning chamber. Therefore, it is necessary to reduce waiting times between removals of the pigs from the stunning chamber and performing exsanguination. Under no circumstances should this interval exceed 60 s, otherwise the pigs may recover sensitivity. The study recommends maintaining strict control of entry into, and removal from, the CO2 chamber in order to avoid backlogs in the slaughtering area and so ensure that the pigs do not regain consciousness.
... Several studies used time to loss of posture as a criterion for assessing when pigs start to lose consciousness during CO 2 stunning (Llonch et al., 2013;Velarde et al., 2007). However, Raj and Gregory (1996) determined that while loss of posture was an indicator of the onset of unconsciousness, it did not exclusively indicate that complete unconsciousness was present. This was confirmed by Rodriguez et al. (2008), as brain activity measured with EEC continued during the first onset of muscle excitation, several seconds after the loss of posture. ...
... The gas mixture and in particular the CO 2 concentration in the stunning pit can heavily influence the time to unconsciousness (Raj & Gregory, 1996;Velarde et al., 2007;Verhoeven et al., 2016). Our results were thus only compared with studies that used a similar CO 2 concentration, i.e. 90% or close to 90%. ...
Article
Despite raising animal welfare concerns, stunning of pigs with CO2 prior to slaughter remains the most widely applied method in commercial settings. The aim of this study was to assess the discomfort period and its influencing factors in fattening pigs and sows in a commercial slaughterhouse. The discomfort period was defined as the first reaction to the gas or the environment from the point the animal enters the gondola, until complete relaxation of its head. Results showed that the discomfort period lasted 11 s longer in sows than in pigs, and that certain behaviors occurred distinctly later in sows as compared to pigs. Furthermore, higher humidity and temperature in the pit could prolong the duration of the discomfort period. Further research is needed to better understand the underlying physiological processes for both the differences seen between sows and fattening pigs as well as the influence of ambient parameters.
... Los efectos del CO 2 actúan por dos vías: la primera, causando irritación en la mucosa de las membranas nasales; y la segunda, como un agente que estimula fuertemente el centro respiratorio, provocando hiperventilación y sofocación antes perder la consciencia. Durante la inhalación, la 'pérdida de la postura' ha sido considerado como el primer indicador conductual justo antes de perder completamente la consciencia (Raj & Gregory 1996;Rodríguez et al., 2008). ...
... Aunado a ello, observé que la 'pérdida de la postura' aparece a partir de los 11 s (T 2 ) de haber iniciado el aturdimiento, lo que pudiera indicar que es aquí donde inicia la pérdida de la consciencia y el cerdo pierde la fuerza de sus cuatro extremidades, golpeando la pared o el piso de la juala de forma violenta; éste fenómeno puede ir acompañado de 'intentos para incorporarse' en algunos de los casos. La 'pérdida de la postura' ha sido reportado en otros estudios, donde los cerdos dejan de estar 'de pie' después de los 22 s de haber iniciado el aturdimiento (80% CO 2 ) (Raj & Gregory, 1996); años mas tarde, Gerritzen et al., (2008) mencionaron que cerdos adoptaron 'sentado' a los 16 ± 0.8 s de haber iniciado el aturdimiento con una combinación de gases (70% CO 2 +30% O 2 ), y eventualmente, perdieron la postura a partir de los 24±1 s. ...
... In 2009, the European Union (EU) adopted Council Regulation (EC) No 1099/2009 'on the protection of animals at the time of killing', which was prepared on the basis of two Scientific Opinions adopted by the European Food Safety Authority (EFSA) in 2004and 2006. In 2013 another Scientific Opinion related to this subject. ...
... The main cause of respiratory distress is increased CO 2 levels in blood (Raj, 2006), a strong respiratory stimulator that induces a sense of breathlessness and air hunger before loss of consciousness (Beausoleil and Mellor, 2015). It can also be induced by the lack of oxygen or hypoxaemia during killing by inert gas mixtures (Beausoleil and Mellor, 2015). ...
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Abstract Pigs at different stages of the production cycle may have to be killed on‐farm for purposes other than slaughter (where slaughter is defined as killing for human consumption) either individually (e.g. severely injured pigs) or on a large scale (e.g. unproductive animals or for disease control reasons). This opinion assessed the risks associated with the on‐farm killing of pigs and included two phases: 1) handling and moving of pigs and 2) killing methods (including restraint). The killing methods were subdivided into four categories: electrical methods, mechanical methods, gas mixture methods and lethal injection. Four welfare consequences to which pigs can be exposed to during on‐farm killing were identified: pain, fear, impeded movement and respiratory distress. Welfare consequences and relevant animal‐based measures were described. In total, 28 hazards were associated with the welfare consequences; majority of the hazards (24) are related to Phase 2 (killing). The main hazards are associated with lack of staff skills and training, and poor‐designed and constructed facilities. Staff was identified as an origin of all hazards, either due to lack of skills needed to perform appropriate killing or due to fatigue. Corrective measures were identified for 25 hazards. Outcome tables linking hazards, welfare consequences, animal‐based measures, hazard origins, preventive and corrective measures were developed and mitigation measures proposed.
... Carbon dioxide was first proposed in the mid-1950s for the pre-slaughter stunning of poultry (Raj et al., 1996). Gas stunning, also called controlled atmosphere stunning (CAS), has become more common during the last 20 years because of its advantages in animal welfare (although some argue that there is an aversive stage that suggests the animal is being agitated) and product quality compared to the water-bath method. ...
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There has always been a debate about the acceptability of stunning methods for preparing Halal slaughtered meat. Throughout the last few decades, stunning methods have become acceptable for Halal slaughtering due to an increasing majority of Muslim countries issuing Fatwas (religious rulings) that approve of stunning methods for the Halal slaughtering of food animals. With an increasing Muslim population worldwide, Halal meat provision is important for Muslims both economically and ethically. Moreover, there have been concerns regarding traditional Halal slaughter without the use of stunning from the standpoint of the animal’s welfare. This article reviews the different stunning methods available and the associated processing practices, addressing their pros and cons in the commercial production of Halal meat.
... 7 Argon (Ar) has been proposed as an alternative gas euthanasia method. 8 The European Food Safety Authority recommends stunning pigs with a 30:60 ratio of CO 2 to Ar or a 90:10 ratio of Ar to air. 9 Argon is a noble gas, and as such is likely unreactive throughout the physiological systems. 10 Loss of consciousness and death are produced through hypoxia, creating the physiological state of hypocapnic anoxia. ...
Article
Objectives: To assess effects of swine respiratory disease (SRD) on nursery pig responses during gas euthanasia and to com-pare responses to carbon dioxide (CO2) and argon (Ar) gas euthanasia in terms of efficacy and welfare. Materials and methods: Fifty-four pigs iden-tified for euthanasia were classified as having SRD or euthanized for other reasons (OT). These pigs were distributed among three treatments: prefill CO2 (P-CO2), gradual fill CO2 (G-CO2), and prefill Ar (P-Ar). Behav-ioral and physiological indicators of efficacy and welfare were assessed directly and from video. Modified atmosphere CO2 and O2 concentrations (%) were collected through-out the process. Results: Respiratory disease status did not affect behavioral or physiological responses associated with efficacy or welfare with P-CO2 or G-CO2. Conversely, SRD pigs lost consciousness faster than OT pigs with P-Ar {P < .05) and duration of open-mouth breathing was shorter (P < .05), but dura-tion of ataxia tended to be longer (P < JO). Regardless of disease status, P-CO 2 was associated with superior animal welfare, with shorter latency to loss of consciousness than P-Ar, and shorter duration of ataxia and duration and intensity of righting responses. Implications: Standard operating procedures for gas euthanasia utilizing CO2 or Ar do not require adjustment for nursery pigs with respiratory disease. Minimum exposure of ft) minutes at > 70% CO2concentration is required to reliably produce respiratory arrest in nursery pigs. Argon is not recommended as a euthanizing agent for nursery pigs. Duration of exposure to Ar required to reliably produce respiratory arrest remains unknown.
... 11,12 Although Duroc and Large White pigs will tolerate 30% CO 2 to gain access to a food reward, hypoxia produced by inhalation of the inert gases nitrogen or argon has been proposed by others as less aversive alternatives to CO 2 for pre-slaughter stunning of swine. [12][13][14][15] However, early removal from argon or nitrogen stunning-gas mixtures results in rapid return to consciousness. Thus, when inert gases are used for euthanasia, O 2 levels < 2 volume percent and exposure times > 7 minutes are required to ensure killing. ...
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Objective: To determine the effect of physical and inhaled euthanasia methods on mean plasma levels of three hormonal stress indicators in young pigs. Materials and methods: Plasma concentrations of Cortisol, norepinephrine, and lactate were determined immediately before and after two-step electrocution (n = 39; 7.1 ± 0.5 kg), captive bolt (n = 61; 12.3 ± 1.9 kg), 70% N2/30% CO2 at a displacement rate equivalent to 20% of the chamber volume per minute (n = 16; 2.3 ± 0.3 kg), and 100% CO 2 at 10% (n = 4; 1.9 ± 0.2 kg) and 20% (n = 12; 1.9 ± 0.1 kg) chamber volume displacement rate per minute. Results: Mean Cortisol concentrations did not differ following captive bolt, electrocution, and 70% N2/30% CO2 or 100% CO2 at 20% of the chamber volume per minute (P >. 05). The decrease in Cortisol concentrations with 100% CO2 at 10% of the chamber volume per minute was different (P <. 05) than the increase observed with 100% CO2 at 20% of the chamber volume per minute and different (P <. 05) than the increase observed with captive bolt; however, differences were small. All methods increased mean lactate and norepinephrine concentrations post euthanasia, with no observed differences between methods. Times to loss of consciousness and loss of heartbeat were shorter with CO2 than with 70% N2/30% CO2 (P <. 05). Implications: Gradual displacement administration of CO2 and 70% N2/30% CO2 produce similar plasma concentrations of stress indicators as physical euthanasia methods in young pigs.
... Most modern gas stunning systems allow pigs to stay in groups during the stunning process, considered an advantage for animal welfare, as pigs are gregarious. On the negative side, at a concentration of 80% CO2, the induction of consciousness needs 21 to 30 s, a period during which pigs exhibit apparent respiratory distress, as well as muscular contractions and convulsions [4][5][6][7][8][9]. Pigs may further express avoidance reactions, also indicative of the aversiveness of high CO2 concentrations [10][11][12]. ...
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A total of thirty pigs were experimentally slaughtered using gas (80% CO2 in air, 90 s; 30% CO2/70% N2O; 90 s) or electrical stunning (1.3 A, 10 s). Stunning may accelerate post-mortem muscle metabolism, due to psychological stress and/or muscle contractions. The specific effects of the stunning method were studied by limiting pre-stunning physical activity and stress: pigs were driven in a trolley from the rearing to the stunning site (6.5 m) and immediately slaughtered. Bleeding efficiency and carcass characteristics were similar and satisfactory for all stunning methods. Early post-mortem pH decline in the Longissimus lumborum was faster following gas compared to electrical stunning. The pH of other muscles was not influenced; color and drip loss showed minor effects. Hence, results are in contrast to current beliefs: compared to electrical stunning, following gas stunning, the stress and muscle contractions during the induction of unconsciousness have a slightly greater impact on Longissimus lumborum muscle metabolism; differences are minor and limited to certain muscles only.
... This is caused by the formation of carbonic acid when CO 2 in the chamber comes into contact with moisture, thereby stimulating nociceptors in the mucosa and producing an uncomfortable burning sensation (AVMA Members of the Panel on Euthanasia, 2013;Coates, 2001;Gregory, Raj, Audsley, & Daly, 1990). Therefore, it is considered that CO 2 is pungent to inhale and can produce a state of breathlessness (Raj & Gregory, 1996). ...
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Guinea pigs (Cavia porcelus) are an important source of nonhuman animal protein in the Andean region of South America. Specific guidelines regarding the welfare of guinea pigs before and during slaughter have yet to be developed. This study critically assessed the humaneness of 4 different stunning/slaughter methods for guinea pigs: cervical neck dislocation (n = 60), electrical head-only stunning (n = 83), carbon dioxide (CO2) stunning (n = 21), and penetrating captive bolt (n = 10). Following cervical neck dislocation, 97% of guinea pigs had at least 1 behavioral or cranial/spinal response. Six percent of guinea pigs were classified as mis-stunned after electrical stunning, and 1% were classified as mis-stunned after captive bolt. Increased respiratory effort was observed during CO2 stunning. Apart from this finding, there were no other obvious behavioral responses that could be associated with suffering. Of the methods assessed, captive bolt was deemed the most humane, effective, and practical method of stunning guinea pigs. Cervical neck dislocation should not be recommended as a slaughter method for guinea pigs.
... For example, exposure of rats at concentrations of 30 and 100% CO 2 induces unconsciousness after 150 and 54 s of inhalation, respectively (Sharp et al., 2006). In pigs, the delays until loss of posture were 38, 34, 25, 17, 22 and 15 s for exposures to 40, 50, 60, 70, 80 and 90% of CO 2 in air (Raj and Gregory, 1996). Other studies found that loss of brain responsiveness ...
... La durée et la forme de ces réactions dépendent de la concentration en CO 2 . La majorité des porcs immergés dans des concentrations entre 40 et 70 % de CO 2 montre des réactions de fuite (11). À des concen- ...
... In that study, 50% of the pigs exhibited muscle jerking; of those animals, 41% showed jerking before loss of posture, 39% at the time of loss of posture, and 20% after loss of posture. Following Raj and Gregory (1996), muscle jerking before, or at the same time as, the loss of posture is associated with conscious animals performing escape attempts. On the other hand, muscle jerks after loss of posture are associated with involuntary convulsions in unconscious animals (Forslid 1987(Forslid , 1992. ...
Article
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The principal objective of this review is to characterize the physiological and biochemical: events that occur in swine when stunned with carbon dioxide (CO2) prior to slaughtering, as they relate to issues of animal welfare. Stress responses promote the maintenance of homeostasis and adaptation to the physiological and psychosocial challenges of a changing environment, a complex process that involves the coordinated activation of behavioural, autonomic and neuroendocrine reactions. When respired, CO2 combines with water to form H2CO2 (carbonic acid), which generates elevated concentrations of H+ ions that result in a state of acidosis at the cellular level. Today, questions have been raised concerning animal welfare, as some fear that inhaling high concentrations of CO2 may cause distress in animals before they lapse into a state of unconsciousness. In particular, the bodily movements observed in the early phase of CO2-induced anaesthesia in swine have led to concerns about stress. Pigs exposed to 80% CO2 for 60 sec experience lactic academia and respiratory and metabolic acidosis. Lactate levels are an indicator of stress, while it has been shown that blood lactate concentrations associated with pre-slaughter stress factors (e.g., aggressive handling immediately prior to stunning) have detrimental effects on pork quality. From the perspective of animal welfare, 90% argon by volume, or the lowest possible CO2 concentration necessary to stun swine, is recommended. Argon is suggested as a welfare-friendly alternative to carbon dioxide for stunning/killing pigs and poultry.
... The latency to loss of posture is known to vary according to CO 2 concentration (Raj and Gregory, 1996;Raj, 1999;Velarde et al., 2007;Llonch et al., 2013). While we attempted to measure actual CO 2 concentration in the gondola during the full cycle, it was logistically impractical to measure CO 2 concentrations continuously, while the pigs were being stunned. ...
Article
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The stunning process is an important component of slaughter with implications for animal welfare due to the potential distress and pain in the case of a sub-effective or lengthy stun. This study examined the factors correlated with variation in responses to carbon dioxide (CO2) stunning of pigs in five Australian commercial abattoirs. A total of 1769 pigs (199-492 focal pigs per abattoir) were individually followed from lairage to post-stunning. A standardised observation protocol was used based on a literature review of the pre-slaughter factors that may influence the reaction to CO2 stunning, such as animal background, lairage conditions, handling, stunning system and conditions. Pigs lost posture 22.5 ± 0.2 s after commencement of descent of the gondola into the CO2 chamber. Latency to loss of posture was associated with farm of origin and time of day, which could be linked to various factors. Pigs that crawled or attempted to escape while in the gondola within the CO2 chamber took longer to lose posture. Crawl and escape attempts differed between abattoirs (0.6-46.2% of the pigs observed) as well as mounting other pigs (1.0-24.3%). Greater amounts of forceful contacts during handling in the race were related to more mounting in the gondola, but to less pigs crawling or attempting to escape. Mounting in the gondola was more frequent for pigs from lairage pens of mixed sexes, followed by pens of entire males and finally pens of females. Males were also twice as likely to show crawl and escape attempts than females. Gasping in the gondola was relatively frequent (63.1-81.8%) and was associated with higher activity in the lairage pen and higher skin injuries. Convulsions (60.1-69.6%) were generally observed after loss of posture. The type of CO2 system (group-wise vs single-file loading) had no significant effect on behaviour in the gondola. Nevertheless, pigs slaughtered in abattoirs with group-wise loading systems and automatic gates had lower cor-tisol concentrations post-stunning, which may be linked to minimal handling by stockpeople, other factors related to the systems, or differences in timing of when blood samples were taken. In conclusion, substantial variation in the reaction of pigs to CO2 stunning was observed between and within abattoirs using a uniform protocol for data collection. This variation in outcomes between abattoirs and stunning systems and the relationships between handling and behavioural outcomes indicates that improvements can be made to reduce aversive responses to CO2 stunning. In particular, avoiding mixing pigs of different sexes in lairage and aversive handling in the race may reduce aversive response to CO2 stunning.
... Although CO 2 is very commonly used for preslaughter stunning, due to a lack of alternatives, C0 2 produces strong aversion (irritation and asphyxia) in pigs before they lose consciousness [23,24]. Isoflurane inhalation was found in one large scale study to only have given sufficiently anaesthesia in 77% of the piglets [25]. ...
Article
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Background: In 2010, the ‘European Declaration on alternatives to surgical castration of pigs’ was agreed. The Declaration stipulates that from January 1, 2012, surgical castration of pigs shall only be performed with prolonged analgesia and/or anaesthesia and from 2018 surgical castration of pigs should be phased out altogether. The Federation of Veterinarians of Europe together with the European Commission carried out an online survey via SurveyMonkey© to investigate the progress made in different European countries. This study provides descriptive information on the practice of piglet castration across 24 European countries. It gives also an overview on published literature regarding the practicability and effectiveness of the alternatives to surgical castration without anaesthesia/analgesia. Results: Forty usable survey responses from 24 countries were received. Besides Ireland, Portugal, Spain and United Kingdom, who have of history in producing entire males, 18 countries surgically castrate 80% or more of their male pig population. Overall, in 5% of the male pigs surgically castrated across the 24 European countries surveyed, castration is performed with anaesthesia and analgesia and 41% with analgesia (alone). Meloxicam, ketoprofen and flunixin were the most frequently used drugs for analgesia. Procaine was the most frequent local anaesthetic. The sedative azaperone was frequently mentioned even though it does not have analgesic properties. Half of the countries surveyed believed that the method of anaesthesia/analgesia applied is not practicable and effective. However, countries that have experience in using both anaesthesia and post-operative analgesics, such as Norway, Sweden, Switzerland and The Netherlands, found this method practical and effective. The estimated average percentage of immunocastrated pigs in the countries surveyed was 2.7% (median = 0.2%), where Belgium presented the highest estimated percentage of immunocastrated pigs (18%). Conclusion: The deadlines of January 1, 2012, and of 2018 are far from being met. The opinions on the animalwelfare- conformity and the practicability of the alternatives to surgical castration without analgesia/anaesthesia and the alternatives to surgical castration are widely dispersed. Although countries using analgesia/anaesthesia routinely found this method practical and effective, only few countries seem to aim at meeting the deadline to phase out surgical castration completely.
... Behavioural indicators Loss of posture, the inability of the animal to remain in an initial standing or sitting position, is considered a valuable indicator as it is often the first sign to be lost after successful stunning and indicates that the cerebral cortex is no longer able to control posture (Raj et al., 1992;Raj and Gregory, 1996;Llonch et al., 2013). Both mechanical and electrical stunning should lead to immediate collapse (AVMA, 2013). ...
Article
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Assessing unconsciousness is important to safeguard animal welfare shortly after stunning at the slaughter plant. Indicators that can be visually evaluated are most often used when assessing unconsciousness, as they can be easily applied in slaughter plants. These indicators include reflexes originating from the brain stem (e.g. eye reflexes) or from the spinal cord (e.g. pedal reflex) and behavioural indicators such as loss of posture, vocalisations and rhythmic breathing. When physically stunning an animal, for example, captive bolt, most important indicators looked at are posture, righting reflex, rhythmic breathing and the corneal or palpebral reflex that should all be absent if the animal is unconscious. Spinal reflexes are difficult as a measure of unconsciousness with this type of stunning, as they may occur more vigorous. For stunning methods that do not physically destroy the brain, for example, electrical and gas stunning, most important indicators looked at are posture, righting reflex, natural blinking response, rhythmic breathing, vocalisations and focused eye movement that should all be absent if the animal is unconscious. Brain stem reflexes such as the cornea reflex are difficult as measures of unconsciousness in electrically stunned animals, as they may reflect residual brain stem activity and not necessarily consciousness. Under commercial conditions, none of the indicators mentioned above should be used as a single indicator to determine unconsciousness after stunning. Multiple indicators should be used to determine unconsciousness and sufficient time should be left for the animal to die following exsanguination before starting invasive dressing procedures such as scalding or skinning. The recording and subsequent assessment of brain activity, as presented in an electroencephalogram (EEG), is considered the most objective way to assess unconsciousness compared with reflexes and behavioural indicators, but is only applied in experimental set-ups. Studies performed in an experimental set-up have often looked at either the EEG or reflexes and behavioural indicators and there is a scarcity of studies that correlate these different readout parameters. It is recommended to study these correlations in more detail to investigate the validity of reflexes and behavioural indicators and to accurately determine the point in time at which the animal loses consciousness.
... Inhalation of carbon dioxide induces respiratory and metabolic acidosis, which reduces the pH of blood and cerebrospinal fluid, thereby inducing a state of analgesia and anaesthesia in the animal (Raj 2008). Research has shown that the rate of induction of unconsciousness with carbon dioxide depends on the concentration of this gas in the stunning unit (Troeger and Woltersdorf 1991;Raj and Gregory 1996). Following a proposal of the EC Scientific Veterinary Committee (1997), a concentration of at least 80% CO 2 has been implemented in different EU national regulations since 1999. ...
Article
Besides creating a reservoir of animals aimed at maintaining the constant speed of the slaughter line, the function of lairage is to allow the animals to recover from the stress of transport and unloading. However, inadequate treatment of slaughter pigs in this stage or lack of environmental control may result in additional stress leading to economic losses due to poor animal welfare (deads-on-arrival and downers), skin damage and poor meat quality. Short and long lairage times can result in increased incidences of pale, soft, exudative and dark firm, dry pork, respectively. However, these effects are influenced by the environmental conditions and the pig genotype. Mixing unfamiliar pigs increases skin damages due to fighting, but keeping pigs in small groups or at high stocking density may limit this effect. Research is needed to identify alternative tools to the electric prod and to design a stunning chute enabling a smooth flow of pigs into the stunner.
... Heavy breathing and open-mouth breathing are signs of breathlessness which is associated with unpleasantness and compromised welfare [6,15]. Open-mouth breathing is a behavior that is typically observed before loss of posture when using CO 2 [8,16]. The latency to heavy breathing and open-mouth breathing were longer in the N 2 O treatment than in the CO 2 treatment, and occurred after loss of posture and after the N 2 O had been switched to CO 2 in the chamber. ...
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Current methods of euthanizing piglets are raising animal welfare concerns. Our experiment used a novel two-step euthanasia method, using nitrous oxide (N₂O) for six minutes and then carbon dioxide (CO₂) on compromised 0- to 7-day-old piglets. A commercial euthanasia chamber was modified to deliver two euthanasia treatments: the two-step method using N₂O then CO₂ (N₂O treatment) or only CO₂ (CO₂ treatment). In Experiment 1, 18 piglets were individually euthanized. In Experiment 2, 18 groups of four to six piglets were euthanized. In the N₂O treatment, piglets lost posture, indicating the onset of losing consciousness, before going into CO₂ where they showed heavy breathing and open-mouth breathing; whereas piglets in the CO₂ treatment did not lose posture until after exhibiting these behaviors (p ≤ 0.004). However, piglets in the N₂O treatment took longer to lose posture compared to the CO₂ treatment (p < 0.001). Piglets in the N₂O treatment displayed more behavioral signs of stress and aversion: squeals/minute (p = 0.004), escape attempts per pig (p = 0.021), and righting responses per pig (p = 0.084) in a group setting. In these regards, it cannot be concluded that euthanizing piglets for 6 min with N₂O and then CO₂ is more humane than euthanizing with CO₂ alone.
... Concentrations of CO 2 < 30 volume percent are seemingly not aversive to pigs. 4,5 Carbon dioxide produces quicker loss of consciousness than inert gas hypoxia when administered by gradual displacement methods, 6 and gradual displacement administration of CO 2 is less likely to cause pain due to ocular and nasal nociceptor activation prior to loss of consciousness. 1 Further, when CO 2 is gradually administered to young pigs at a constant displacement rate of either 10% or 20% of the container volume per minute, unconsciousness occurs within 80 to 124 seconds at approximately 22 volume percent CO 2 concentration, and the increase in plasma concentrations of cortisol, norepinephrine, and lactate after exposure to CO 2 do not differ from those observed following the physical methods of captive bolt and electrocution. 6 Unlike nitrogen and argon, which must be held within a very tight range of concentration to reduce oxygen (O 2 ) levels below 2% of the total volume for effective killing, CO 2 can render pigs unconscious and kill over a wide range of concentrations, even when O 2 is greater than 2% of the total volume. ...
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et al. Carbon dioxide system for on-farm euthanasia of pigs in small groups. Summary Certain swine-farm operations require the regular euthanizing of multiple pigs on almost a daily basis. These animals may be too large for the small-scale methods of euthanasia used for nursing pigs and therefore may require the use of individual mechanical methods approved by the American Veterinary Medical Association (AVMA), such as gunshot and captive bolt. These methods may be unpleasant for workers and pose additional handling and carcass-disposal challenges. Considerable research has been done using the AVMA-recommended carbon dioxide (CO 2) method for mass depopulation of swine in the case of an exigent situation. This paper details a method for adapting that CO 2 methodology for euthanizing small groups of pigs. The system does not require direct worker contact with individual animals or manual handling of carcasses. The concept involves use of a standard high-pressure CO 2 cylinder and a small euthanasia chamber,
... As the Polish Constitutional Tribunal noted: 'it is too often overlooked that the current law also permits various methods of animal slaughter with prior stunning which inevitably induce suffering, pain and distress to animals'. 64 Methods such as the CO 2 asphyxiation of pigs and electrically stunning of chickens are well documenting as causing significant suffering (Gregory 1996;Shields and Raj 2010). ...
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In February 2019, The Royal Society for the Prevention of Cruelty to Animals (RSPCA) and the British Veterinary Association (BVA) published a joint open letter to the British Government calling for a repeal of a legal exemption that permits the slaughter of animals without prior stunning. The RSPCA and BVA argue that repealing the exemption is required on grounds of animal welfare, claiming that non-stun slaughter causes unnecessary pain and suffering. By contrast, Islamic and Jewish groups assert that non-stun slaughter, when properly conducted, is both humane and a religious requirement for least some followers of their faiths. This article considers whether imposing a ban on non-stun slaughter is compatible with obligations to protect religious freedom and non-discrimination under the European Convention of Human Rights. It will conclude that it can be and, when done to protect animal welfare, falls within Contracting States’ margin of appreciation.
... To date, varying degrees of these convulsive movements have been reported following application of all available euthanasia techniques for piglets of this size including BFT and NPCB (Chevillon et al., 2004;Widowski et al., 2008;J. A. Woods, unpublished data) and CO 2 (Raj and Gregory, 1996;Sutherland, 2010;Sadler, 2013). The convulsive period was slightly longer than the 1 to 1.5 min typically seen with BFT (Widowski et al., 2008;Chevillon et al., 2004), but was similar to other NPCB devices falling within the range or 1 to 4 min reported by J. A. Woods (unpublished data) and similar to the 2 min reported by Widowski et al. (2008). ...
Article
The objective of this study was to determine the effectiveness of a nonpenetrating captive bolt, Zephyr-E, for euthanasia of suckling and weaned pigs from 3 to 9 kg (5-49 d of age) using signs of insensibility and death as well as postmortem assessment of traumatic brain injury (TBI). The Zephyr-E was used by 15 stock people to euthanize 150 compromised pigs from 4 farrowing and nursery units from commercial farms and 2 research stations. Brainstem reflexes, convulsions, and heartbeat were used to assess insensibility, time of brain death, and cardiac arrest following Zephyr-E application. Skull fracture displacement (FD) was quantified from computed tomography (CT) scans (n = 24), macroscopic scoring was used to assess brain hemorrhage and skull fracture severity (n = 150), and microscopic scoring was used to assess subdural hemorrhage (SDH) and parenchymal hemorrhage within specific brain regions that are responsible for consciousness and vital function (n = 32). The Zephyr-E caused immediate, sustained insensibility until death in 98.6% of pigs. On average, clonic convulsions (CC) ceased in 82.2 s (±3.4 SE), brain death was achieved in 144.9 s (±5.4 SE), and cardiac arrest occurred in 226.5 s (±8.7 SE). Time of brain death and cardiac arrest differed significantly among stock people (P = 0.0225 and P = 0.0369). Age was positively related to the duration of CC (P = 0.0092), time of brain death (P = 0.0025), and cardiac arrest (P = 0.0068) with shorter durations seen in younger pigs. Average FD was 8.3 mm (±1.0 SE). Macroscopic scores were significantly different among weight classes for subcutaneous (P = 0.0402) and subdural-ventral (P = 0.0037) hemorrhage with the lowest severity hemorrhage found in the 9-kg weight category. Microscopic scores differed among brain sections (P = 0.0070) for SDH with lower scores found in the brainstem compared to the cerebral cortex and midbrain. Parenchymal hemorrhage differed among brain sections (P = 0.0052) and weight categories (P = 0.0128) with the lowest scores in the midbrain and brainstem and the 7- and 9-kg weight categories. The Zephyr-E was highly effective for the euthanasia of pigs up to 9 kg (49 d) based on immediate insensibility sustained until death. Postmortem results confirmed that severe skull fracture and widespread brain hemorrhage were caused by the Zephyr-E nonpenetrating captive bolt.
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Inhalation of concentrations greater than 30% of carbon dioxide (CO2) by volume in atmospheric air causes aversion in pigs. The objective of this study was to assess, using aversion learning techniques and behavioural studies, the aversion to three alternative gas mixtures of nitrogen (N2) and CO2: 70% N2 and 30% CO2 (70N30C), 80% N2 and 20% CO2 (80N20C) and 85% N2 and 15% CO2 (85N15C). The experiment consisted of two trials of three groups of ten pigs each. Pigs were placed individually at the starting point of the test facility and allowed to enter the crate of a dip-lift stunning system during one control session with atmospheric air and three treatment sessions with one of the gas treatments in each group. When the pit contained any of the three gas mixtures, the time taken to cross the raceway and enter the crate did not increase compared to the control session. However, when exposed to the gas mixtures, the majority (85.80%) of pigs performed attempted retreats in the crate, 22.22% exhibited escape attempts, and 7.91% vocalised, without differences between gas mixtures. The percentage of pigs gasping was higher when exposed to 70N30C compared to 80N20C and 85N15C. The results suggest that pigs show signs of aversion to the inhalation of 15 to 30% CO2 in nitrogen atmosphere compared to atmospheric air but the aversion response did not increase in consecutive sessions.
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Stunning by inhalation of nitrogen (N2) and carbon dioxide (CO2) mixtures reduces aversion compared to high concentrations of CO2 in pigs and poultry. The objective of the study was to assess the aversion to 90% of CO2 (90C) and an alternative gas mixture of 80% N2 and 20% CO2 (80N20C) in commercial rabbits (Oryctolagus cuniculus). Sixty animals, divided into two groups, were used. During the first day, the rabbits of both groups were lowered in pairs into the pit with atmospheric air and their behaviour was recorded as control. During the second day, one group was exposed, again in pairs, to 90C and the other to 80N20C for 1 min. Exploratory behaviour and general activity were assessed 2 min before the exposure, during the exposure and for 2 min subsequently. During the exposure, signs of respiratory distress, loss of balance, muscle twitching and recovery of balance were also assessed. In the control sessions (atmospheric air), animals did not show respiratory distress or muscle twitching and were less active while the crate was descending than when gas treatments were applied. The percentage of animals with respiratory distress was higher in 90C (97%) than 80N20C (40%). Muscle twitching occurred earlier in 80N20C (97%; 23.9 s) than in 90C (17%; 37.4 s). A second phase of muscle twitching occurred only in 90C at 93.0 s. Mean latency of lost of balance and recovery were lower in 80N20C (24.2 and 98.6 s, respectively) than in 90C (28.2 and 110.2 s, respectively). It is concluded that rabbits showed less signs of respiratory distress to inhalation of 80N20C than 90C but more signs of aversion than when they were exposed to atmospheric air.
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Severely depressed pigs exhibit differences in a number of important parameters that may affect gas euthanasia, including decreased respiration rate and tidal volume. Hence, the objectives of this study were to assess the efficacy and animal welfare implications of gas euthanasia of suckling pigs with varied disease severity (severely depressed [DP] vs other [OT]). A 2 × 2 factorial design was utilised with two gas types (carbon dioxide [CO2]; argon [Ar]) and two flow rates (G = gradual, 35% box volume exchange per min [BVE min–1]; P = prefill + 20% BVE min–1). Sixty-two pigs were enrolled and tested as DP/OT pairs in each gas treatment combination. Pigs identified for euthanasia were assigned a subjective depression score (0 = normal to 3 = severely depressed). Pigs scored 3 and ≤ 1 were categorised as DP and OT, respectively. Significantly lower respiration, rectal temperature, pulse and weight were observed for the DP pigs relative to OT. Pigs were assessed for behavioural indicators of efficacy and welfare. No differences were observed between DP and OT when using P-CO2 or G-CO2. However in P-Ar, DP had greater latency to loss of consciousness relative to OT (212 [± 22] vs 77 [± 22] s), decreased latency to last limb movement (511 [± 72] vs 816 [± 72] s), greater duration of open-mouth breathing (151 [± 21] vs 69 [± 21] s), decreased duration ataxia (101 [± 42] vs 188 [± 42] s) and decreased righting response (27 [± 11] vs 63 [± 11] s). The G-Ar treatment was removed due to ethical concerns associated with prolonged induction. In conclusion, depression score did not affect pig responses to euthanasia with CO2 gas, but did affect responses to Ar. Furthermore, Ar was associated with a prolonged euthanasia process, including frequencies and durations of distress behaviours.
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The stability and uniformity of the following gas mixtures: 90% argon; 85% argon and 15% carbon dioxide (CO2); 70% argon and 30% CO2; 98% nitrogen (N2); 92% N2 and 8% CO2; 90% N2 and 10% CO2; 85% N2 and 15% CO2; 80% N2 and 20% CO2; 70% N2 and 30% CO2; and 90% CO2 by volume in atmospheric air were assessed in a commercial dip-lift stunning system when the cradle was either stationary or in motion. The gas mixtures of 90% argon, 85% argon and 15% CO2, 70% argon and 30% CO2, 85% N2 and 15% CO2, 80% N2 and 20% CO2, 70% N2 and 30% CO2 and 90% CO2 by volume in atmospheric air could be sustained in a commercial dip-lift stunning system. The stability of the gas mixtures 92% N2 and 8% CO2, and 90% N2 and 10% CO2 by volume in atmospheric air were lower than in the previous cases. On the other hand, an N2 concentration higher than 94% by volume in atmospheric air could not be sustained in the stunning system. In addition, gas mixtures of argon and CO2 showed a higher stability than gas mixtures of N2 and CO2. The uniformity at different levels inside the pit (defined as the capacity of the gas to maintain its concentration constant at different levels inside the pit) was higher in 90% argon, or argon and CO2 mixtures and N2 and CO2 mixtures than in 90% CO2. This fact ensures that for the whole time the animals are inside the pit, the same conditions are applied, which is not the case for 90% CO2.
Article
This guidance defines the assessment process and the criteria that will be applied by the Animal Health and Welfare Panel to studies on known new or modified legal stunning interventions to determine their suitability for further assessment. The criteria that need to be fulfilled are eligibility criteria, reporting quality criteria and methodological quality criteria. The eligibility criteria are based upon the legislation and previously published scientific data. They focus on the intervention and the outcomes of interest, i.e. immediate onset of unconsciousness and insensibility or absence of avoidable pain, distress and suffering until the loss of consciousness and sensibility, and duration of the unconsciousness and insensibility (until death). If a study fulfils the eligibility criteria, it will be assessed regarding a set of reporting quality criteria that are based on the REFLECT and the STROBE statements. As a final step in this first assessment phase, the methodological quality of the submitted study will be assessed. If the criteria regarding eligibility, reporting quality and methodological quality are fulfilled, a full assessment of the animal welfare implications of the proposed alternative stunning intervention, including both pre-stunning and stunning phases, and an evaluation of the quality, strength and external validity of the evidence presented would be carried out at the next level of the assessment. In the case that the criteria regarding eligibility and reporting quality and methodological quality are not fulfilled, the assessment report of the panel will highlight the shortcomings and indicate where improvements are required before the study can be assessed further. In addition to the assessment criteria, the guidance also specifies general aspects applicable to studies on stunning interventions that should be considered when studying the effectiveness of stunning interventions.
Chapter
Veterinary anesthetists and anesthesiologists are uniquely positioned to contribute meaningfully to matters pertaining to the humane taking of animal life. Determining the humaneness of euthanasia, slaughter, or depopulation methods can be difficult because humans can never fully know or understand the subjective experiences of animals during loss of consciousness. Euthanasia, humane slaughter, and depopulation methods initially produce unconsciousness through three basic mechanisms: direct depression of neurons necessary for life functions; hypoxia; and physical disruption of brain activity. Measurements of brain electrical function, such as electroencephalogram (EEG), bispectral analysis (BIS), and visual and auditory evoked potentials (VEP, AEP), have been used to quantify the unconscious state. Fetal sentience during euthanasia of pregnant animals and ovariohysterectomy of pregnant dogs and cats has been extensively reviewed. Foam depopulation uses medium- or high-expansion foam-generating equipment to create a blanket of water-based foam to cover the animals.
Chapter
This chapter describes advances in pig welfare during lairage and slaughter. The main purpose of lairage is to have sufficient reserve of animal stock in the holding pen to avoid any interruption in the supply of livestock to the slaughter line. Furthermore, it permits animals to recover from the stress and activity resulting from transport and unloading, which can be beneficial to meat quality. However, lairage pigs in a novel environment with unfamiliar pigs might compromise animal welfare and the benefit of providing animals with a resting time can be lost. Moving animals forward to the stunning point can be a very important source of stress if not done properly. Pigs are usually bled by chest sticking. However, prior to the sticking, stunning is mandatory. The chapter covers the general principles of stunning and the main stunning methods, including the monitoring of welfare. The two main stunning systems used in pigs are electricity and gas and in both cases must ensure the animal not recovering the consciousness before death. The chapter also deals with killing for depopulation purposes and describes the available mechanical methods and lethal injections. Finally, the issue of training of the workers is addressed.
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This dissertation explores the different slaughter methods considered humane, which are used and required by law to kill pigs raised for human consumption in the European Union. The main points covered are - the methods required by current EU Regulation 1099/2009 on the protection of animals at the time of killing which include; electrical stunning (head-only and head-body) and gas stunning (carbon dioxide gas and inert gas mixtures). The advantages and disadvantages of these methods are discussed, using results found online from studies and research conducted on the topic, including a list of other methods studied which are not permitted by law but are being looked into and possibly developed as potential alternative stunning methods. The enforcement of this Regulation and the surrounding issues is also touched upon towards the end of the dissertation. In the conclusion, the question of whether any of these methods can be considered truly humane is explored, based on the true definition of the word humane and the results of the studies discussed.
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The aim of the paper was a review of the scientific achievements in physiological stunning and slaughtering mechanisms, control methods of consciousness and their effect on meat quality. Special attention was paid to neurophysiologic phenomena that accompany the process of depriving consciousness before animal deaths using mechanical, electrical and gas stunning methods. These mechanisms are associated with cerebral hypoxia or ischemia or depolarization, acidification and the destruction of cerebral neurons. Such effects can be caused by shock waves, bleeding, electric fields, reduction or arrest of the circulation of blood in the brain, high CO 2 level or low O 2 level in inhaled air or by the mechanical damage of neurons. Some of the stunning methods cause immediate and some gradual consciousness loss. Important factor in the animals’ slaughtering process is the estimation of their consciousness level before bleeding. The indicators of consciousness during mechanical, electrical and gas stunning are discussed within this paper. It is pointed out that at least 2 indicators should be used when estimating animals’ consciousness after stunning e.g. phonic and clonic limb movements and lack of breathing. Ten indicators to control the consciousness were described. The effect of stunning on meat quality is also discussed. It was found that the impact of this process on the quality is not clear. However, the prevailing view is that electric stunning causes effusions and blood haemorrhages in meat. Whereas gas stunning with a CO 2 mixture diminishes the risk of PSE meat. Despite numerous scientific research on the slaughter process there is still deficiency in knowledge on losing consciousness mechanisms and feeling pain. It might be useful to extend the knowledge concerning neurotransmitters and use of magnetic resonance in future studies.
Chapter
This chapter provides an account of the responses of animals to short-term disturbances. The measures of welfare that are used when an individual encounters problems over a timescale of minutes or hours are somewhat different from those used when problems last for days, weeks or years. People may experience and express delight or dismay at experiences lasting for only a few seconds or minutes and these may be important in life or relatively trivial. The situation is the same for other species. Animals respond to handling, transport or painful treatment and their responses can be measured. Some measures are of behaviour while many are of physiology. All are discussed in detail in this chapter. The concept of the magnitude of good or poor welfare, considering both intensity and duration of effect on the individual, is introduced.
Article
The present study used thirty-one pigs to investigate induction of unconsciousness and behavioural reactions in different gas mixtures: 80% CO2/air, 90 s; 40% CO2/30% O2/air, 180 s; 70% N2O/30% CO2, 90 s. All pigs lost consciousness. All presented respiratory difficulties and most pigs involuntary muscle contractions, often before loss of standing posture. Between mixtures, average latencies of certain behaviours and delays between behaviours differed. Following immersion, blood pH was lower than normal. The low pH induced by the CO2/O2/air mixture was physiologically associated with hyperoxemia. Relationships between blood gases, different behavioural and heart rate responses are discussed. In conclusion, all mixtures caused discomfort due to respiratory difficulties and the addition of O2 or N2O to the CO2 mixture did not present an advantage.
Article
Current European Union regulation explicitly states that farmed fish should be spared any avoidable pain, distress or suffering at the time of slaughter. It has been shown that fish suffer when they are killed in an ice slurry, the most common method of killing farmed fish in the Mediterranean. Thus, it is necessary to find a method of slaughtering Mediterranean fish that is, (1) efficient in inducing unconsciousness with minimal pain and distress, (2) practical to be applied to a large group of animals at the same time, and (3) feasible to be used at sea. The present study assesses the welfare of Gilthead seabream (Sparus aurata) stunned by two different gas mixtures authorised for stunning other farmed species. To achieve this objective, commercial sized seabream were stunned and/or sacrificed under different protocols: a) killed directly in ice slurry, b) exposed to a mixture of 30% CO2 + 70% N2, and then moved to ice slurry and c) exposed to a mixture of 40% CO2 + 30% N2 + 30% O2 and then moved to ice slurry. Electroencephalograms (EEG) were recorded to evaluate the state of consciousness of seabream during stunning, while blood and brains were sampled to obtain acute stress indicators and relative gene expression, respectively. Additionally, dead fish were kept for in situ meat quality evaluation. When exposed to the gas mixtures, fish lost balance at 1 min 23 s ± 31 s with CO2 + N2 and 1 min 12 s ± 32 s, with CO2 + N2 + O2, respectively. Cortisol, lactate and glucose levels were significantly lower in all fish exposed to gas prior to ice slurry than in fish slaughtered directly in ice slurry (p < 0.05). Electroencephalogram records indicated that fish started to lose consciousness when they lost balance and sank to the bottom of the tank. No differences were found in the meat quality (pH and rigor mortis) among the three treatments. Altogether, the study concludes that the use of carbon dioxide together with nitrogen prior to immersion in ice slurry is more humane than ice slurry alone.
Article
Meagher, R., Bechard, A., Palme, R., Diez-Leon, M., Hunter, D. B. and Mason, G. 2012. Decreased litter size in inactive female mink (Neovison vison): Mediating variables and implications for overall productivity. Can J. Anim. Sci. 92: 131-141. Farmed mink vary dramatically in activity: very inactive individuals rarely leave the nest-box, while others spend hours active daily, often performing stereotypic behaviour (SB). SB typically correlates with increased reproductive output, and inactivity, with decreased output. Our objectives were to determine whether SB or inactivity best predicted litter size (LS), and to test three hypothesized reasons for inactive dams' reduced LS: HI, excess fat; H2, chronic stress (potentially underlying inactivity because fear motivates hiding); and H3, health problems. We assessed time budgets pre-breeding, scored body condition visually, conducted health exams, and assessed stress using faecal cortisol metabolites (FCM) and "glove tests" for fear. Results did not support H2 and H3: inactive females were no more fearful than active females (P>0.10), they excreted lower levels of FCM (P=0.033), and were considered healthy. As predicted by HI, inactive females had higher body condition scores (P<0.0001), which predicted decreased LS (P=0.040). However, path analysis determined this was unlikely to mediate the inactivity LS relationship. Compared with SB, inactivity more consistently predicted both LS (negatively, P<0.038) and kit weight (positively, P<0.037). Therefore, decreasing inactivity in farmed mink, rather than increasing their SB or decreasing their body condition should most improve productivity.
Article
The aversive effects of 90 per cent argon in air, 30 per cent carbon dioxide in air or 90 per cent carbon dioxide in air were investigated in slaughter weight pigs. A version was assessed from their reluctance to enter the three gaseous atmospheres to obtain a reward (apples). The pigs did not show any aversion to the inhalation of 90 per cent argon in air. The majority of the pigs did not show aversion to the presence of 30 per cent carbon dioxide in air. By contrast, the inhalation of 90 per cent carbon dioxide was aversive to the majority of the pigs. Fasting them for up to 24h prior to testing did not overcome the pigs' reluctance to enter an atmosphere containing 90 per cent carbon dioxide.
  • N G Gregory
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Gregory N G, Mohan Raj A B, Audsley A R S and Daly C C 1990 Effect of CO2 on man. Fleischwirtschaft 70: 1173-1174
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Hoenderken R, Van Logtestjin J G, Sybesma Wand Spanjaard W J M 1979 Kohlendioxid-Betaubung von Schlachtschweinen. Fleischwirtschaft 59: 1572-1578
Germany Forslid A 1992 Muscle spasms during pre-slaughter CO2-anaesthesia in pigs
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Forslid A 1991 Pre-slaughter CO2-anaesthesia in swine-Neurophysiological and ethical aspects. In: Proceedings of 37th International Congress of Meat Science and Technology pp 242-244. Kulmbach. Germany Forslid A 1992 Muscle spasms during pre-slaughter CO2-anaesthesia in pigs. Ethical considerations. Fleischwirtschaft 72: 167-168
Effect of CO2 on man
  • N G Gregory
  • Mohan Raj
  • A Audsley
  • C C Daly
Gregory N G, Mohan Raj A B, Audsley A R S and Daly C C 1990 Effect of CO2 on man. Fleischwirtschaft 70: 1173-1174