No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Welfare Implications of the Gas Stunning of Pigs 2. Stress of Induction of Anaesthesia
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.
... 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. ...
Simple Summary: Animals must be stunned before slaughter to avoid fear, pain, and distress. In pigs, the most extensively used method is exposure to hypercapnia (high (>80%) concentrations of carbon dioxide (CO 2)). However, it produces irritation of the mucosa and a sense of breathlessness, reducing the welfare before slaughter. We investigated whether using hypercapnic-hypoxia (20% CO 2 and less than 2% O 2) reduced aversion and discomfort compared to hypercapnia, and whether the quality of the stunning was adequate, meaning that no animals regain conscious after stunning. Moreover, we compared the impact of both stunning gases for meat and carcass quality. Our results suggest that both gases provoked aversion and discomfort, but these were lower in pigs stunned with the N 2 mixture compared to high CO 2. On the other hand, the stun quality of the N 2 mixture was poorer than high CO 2 stunning, given that more animals regained consciousness before sticking with the N 2 gas mixture. The stunning quality of the N 2 mixture, however, was improved when oxygen concentration was below 2%. Meat quality was slightly poorer in N 2 stunning compared to high CO 2 , with a higher percentage of carcasses showing pale, soft, and exudative pork. Abstract: This study assessed aversion, stunning effectiveness, and product quality of nitrogen and carbon dioxide (CO 2) 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% CO 2 and less than 2% O 2 ; 20C2O) or hypercapnia (90% CO 2 ; 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 O 2 was above 2%, and a slightly poorer pork quality.
... 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. ...
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.
... 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. ...
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.
... 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. ...
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.
... 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. ...
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.
... 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]. ...
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.
... 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). ...
... 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). ...
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 on changes in electroencephalogram (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 346 s after which the corneal reflex and breathing were assessed for 1 min. 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 ± 6 s) than in 95C pigs (33 ± 7 s). Time to an iso-electric EEG was similar in 80C pigs (75 ± 23 s) and 95C pigs (64 ± 32 s). 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 behavioral 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 10 s 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.
... 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. ...
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.
... Moreover, it poses a low risk of errors by operators and ensures a dependable level of stunning effectiveness; when given sufficient exposure time, there is minimal chance of animals regaining consciousness [2,3]. Nonetheless, the method causes concerns regarding animal welfare because of the associated aversive behavior shown during exposure to the gas [4][5][6][7]. The reactions shown before the pig loses its posture (LOP) and thereby loses the ability to remain in a standing or sitting posture can be characterized as a set of conscious behavior patterns such as, e.g., excessive breathing and escape attempts. ...
... "Loss of posture" (LOP) was, in this study, defined as the point when the pig loses the ability to remain in a standing or sitting posture. LOP is used in this study, as in several other experimental studies, as an indicator of the transition to loss of consciousness [6]. It was possible to determine the pigs' first reaction and LOP for the first (sufficiently visible) pig and the last pig by manual observations of the recording. ...
During the CO2 stunning of pigs, a variation in their reaction to the gas and the duration of the induction period is observed. The stunning process can be affected by several conditions, such as stressful events and previous experiences, but the stocking density in the gondola may also have an impact. The objective was to investigate the effect of stocking density on the stunning process under commercial conditions. To quantify the pigs’ reactions under industrial settings with a stocking density of up to eight pigs pr. Gondola (3.91 m2), the activity level was measured using an AI solution. Compared with a simulation of the expected induction period, a significantly longer induction period was found in gondolas containing seven and eight pigs (p < 0.001) but not when the gondolas contained three or four pigs. Both high and mean activity levels were significantly higher when stocking density was increased from three or four pigs to seven or eight pigs. The stunning process was thus negatively affected when increasing the stocking density. More knowledge is needed to explain this effect and to make statements on optimal stocking density. The measured activity levels may be a useful tool for obtaining information under commercial conditions and for documenting animal welfare.
... 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%. ...
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.
... 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). ...
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.
... 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. ...
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.
... The advantages of CO2 stunning are that the modern systems allow the animals to stay in a group that is close to their natural behavior and minimize the incidence of hematomas and bone fractures [8][9][10]. However, the disadvantage is that its effect is not instant and during long stunning animals may become excited [11,12]. ...
In our experiment, the effect of electrical and CO2 stunning on pork meat quality attributes was studied. A total of thirty PIC337 female pigs were allocated to two equal groups which were stunned electrically (50 Hz, 210 V, 2.6 A, 15 s) or by CO2 (85 V% CO2, 15 V% O2, 90 s) and slaughtered at a commercial slaughterhouse. For 24 h post mortem, the carcass m. gluteus medius (GM) was used to evaluate meat quality attributes such as pH, color, hardness, water holding capacity (WHC), and total pigment content, and meat classification was also carried out. The CO2 stunning resulted in muscle with significantly lower pH (p < 0.01) and poorer water holding capacity (p < 0.05) compared to electrical stunning. The GM of pigs stunned electrically showed significantly increased lightness (L*) and redness (a*) (p < 0.05) compared to CO2-stunned. The time course of development of rigor mortis was similar for both stunning methods. Pale, soft, exudative (PSE) or dark, firm, dry (DFD) meat defects were not observed. Based on total pigment content, stunning methods did not significantly affect the amount of removable blood.
... The basis of these concerns is the pain associated with CO 2 inhalation and the potentially associated aversive behaviours animals show on exposure. Previous studies have shown that high concentration of CO 2 is aversive in pigs, induces respiratory distress, and may elicit a fear response [3][4][5][6]. Exposed pigs often vocalize and have vigorous muscle activity before the loss of posture. Importantly, the time from CO 2 exposure to loss of consciousness is still undetermined. ...
... The basis of these concerns is the pain associated with CO 2 inhalation and the potentially associated aversive behaviours animals show on exposure. Previous studies have shown that high concentration of CO 2 is aversive in pigs, induces respiratory distress, and may elicit a fear response [3][4][5][6]. Exposed pigs often vocalize and have vigorous muscle activity before the loss of posture. Importantly, the time from CO 2 exposure to loss of consciousness is still undetermined. ...
Stunning by carbon dioxide (CO2) inhalation is controversial because it is associated with vigorous movements and behaviours which may or may not be conscious reactions. Furthermore, it is unknown whether some behaviours might indicate the transition into unconsciousness. Our study objective was to investigate the loss of consciousness during CO2 stunning by linking physiological variables (in particular pH, PaO2 and PaCO2) to the onset of observed behaviours. A total of 11 cross-bred pigs were studied. A tracheostomy tube, venous and arterial cannulae were placed under sevoflurane anaesthesia. After recovery from this, and a “wash out” period of at least 30 min, arterial blood samples were taken (and baseline values established) before 90–95% CO2 in medical air was administered through the tracheostomy tube. Subsequent behaviours were video-recorded and key physiological variables were evaluated using an anaesthetic monitor and the frequent sampling of arterial blood (albeit with inconsistent inter-sample intervals). After the study, behaviours were classified in an ethogram. At the onset of behaviours categorised as “vigorous movement extremities”, “opisthotonos” and “agonal gasping” pH values (range) were: 6.74–7.34; 6.66–6.96 and 6.65–6.87, while PaCO2 (kPa) was 4.6–42.2, 24.4–51.4 and 29.1–47.6. Based upon these values, we conclude that the pigs were probably unconscious at the onset of “opisthotonos” and “agonal gasping”, but some were probably conscious at the onset of “vigorous movements”.
... The use of carbon dioxide (CO 2 ) has been criticized as highly aversive and distressful to pigs (Raj & Gregory, 1996;Steiner et al., 2019), despite being an approved euthanasia and recommended depopulation method by the AVMA . ...
Animal disease preparedness plans including depopulation guidelines are paramount to prevent the spread of emerging infectious diseases but difficult to implement for swine under field conditions. However, water‐based foam (WBF) is currently an approved and successfully deployed depopulation methodology in poultry. Therefore, the reliability of WBF as a depopulation method and the effectiveness and irreversibility of consciousness and consequential mortality in pigs of different ages was assessed across two trials. Trial 1 investigated the time to loss of consciousness and cessation of cardiac activity in nursery pigs (n = 72) at 6 different foam immersion time points (2.5, 5, 7.5, 10, 12.5, and 15 minutes) when placed in a 1.47m3 (1.2 × 1.2 × 1.02 m, length × width × height) plastic bulk container. One pig per replicate was implanted with an ECG bio‐logger. Irreversible loss of consciousness was observed after a 5‐minute immersion. The average (SD) time to development of a fatal arrhythmia from the initiation of the foam application was 7.3 min (1.82 s). Trial 2 aimed to validate the findings from trial 1 in 75 larger cull sows across 3 replicates (n = 25). Sows were loaded into a 41‐m3 sealed trailer (12.2 × 1.5 × 2.24 m), immersed in WBF, and left undisturbed for 5 minutes post foam‐filling completion. Six pigs in each replicate were implanted with an ECG bio‐logger. A 5‐minute dwell time resulted in irreversible loss of consciousness and subsequent mortality in all cull sows. The average time (SD) to cessation of movement and fatal arrhythmia post foam‐filling completion was 2.2 min (34.8 s) and 8.7 min (138.0 s), respectively. While a 5‐minute immersion in WBF induced irreversible loss of consciousness and death in both trials, a 7.5‐minute dwell time followed by observation for confirmation of death post WBF removal would be advisable for pigs of all sizes. This article is protected by copyright. All rights reserved
... 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. ...
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.
... 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]. ...
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.
... 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. ...
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.
... 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). ...
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.
... 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. ...
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.
... 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]. ...
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.
... 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- ...
... 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 ...
The EFSA Panel on Animal Health and Welfare (AHAW) was asked to deliver a scientific opinion on the use of high‐expansion foam for stunning and killing pigs and poultry. A dossier was provided by the applicant as the basis for an assessment of the extent to which the method is able to provide a level of animal welfare at least equivalent to that ensured by the currently allowed methods for pigs and poultry. According to legislation, to be approved in the EU, new stunning methods must ensure (1) the absence of pain, distress or suffering until the onset of unconsciousness, and (2) that the animal remains unconscious until death. An ad hoc Working Group set up by EFSA performed the assessment as follows: (1) The data provided were checked against the criteria laid down in the EFSA Guidance (EFSA, 2018), and was found to partially fulfil those criteria; (2) extensive literature search; (3) data extraction for quantitative assessment; (4) qualitative exercise based on non‐formal expert elicitation. The assessment led to conclude that it is more likely than not (certainty > 50%–100%) that high‐expansion foam for stunning and killing pigs and poultry, named NEFS in container (Nitrogen Expansion Foam Stunning in container), provides a level of welfare at least equivalent to one or more of the currently allowed methods listed in Annex I of Council Regulation (EC) No 1099/2009. The overall assessment of EFSA is valid only under the technical conditions described in this Opinion for laying hens, broiler chickens of all age and pigs weighing 15–41 kg in situations other than slaughter. The overall assessment of EFSA is that NEFS can be suitable for depopulation using containers for pig and poultry farms respecting the technical conditions and the categories and types of animals defined in this Scientific Opinion.
Infectious animal diseases can cause severe mortality on infected farms. An outbreak challenges the system and forces difficult decisions to stop the disease progression. We propose an ‘all-in-one’ concept of a mobile system for on-farm swine depopulation and pathogen inactivation. The system uses vaporized CO2 followed by heat treatment, broadening options for off-site carcass disposal and cleanup. A direct-fired heater supplies heat into the insulated trailer to reach and maintain the inactivation temperature for targeted pathogens. We developed a user-friendly model based on engineering principles for estimating site- and scenario-specific CO2 amounts and times required to inactivate targeted pathogens. Multipoint CO2 injection and improved distribution to animals follow the plug-flow reactor air replacement model. The model illustrates the depopulation and inactivation of two diseases, African swine fever (ASF) and the porcine reproductive and respiratory syndrome (PRRS) viruses. The model allows for dump trailer size, pig number, weights, and environmental conditions input. Model outputs provide users with practical information about the required CO2 injection rate, temperature setpoints, and times to effectively depopulate and inactivate pathogens in carcasses. The concept could be adopted for a routine or a mass depopulation/treatment/disposal with a single or fleet of ‘all-in-one’ units.
This review investigates about most commonly adopted slaughtering techniques and their comparison with that of the technique, portrayed by Islam. The customary methods of animal slaughtering involve stunning. Ritual kosher which resembles with halal slaughtering method but do not include Tasmiyah, the other one is jhatka slaughtering method which obeys killing of animal by severing the head with single stroke of axe or sword. Whereas, the Islamic slaughtering manner, commonly known as Zabiha, obligates the cut of trachea, food pipe, carotid artery and jugular vein, while reciting the Holy name of Allah. The review framed the documentations of some researches, which clearly reveal that stunning, ritual kosher and jhatka slaughtering cause poor meat quality, highly prone to bacterial attacks, congestion of meat, reduction in shelf life, as well as more the suffering of animal which is clearly against the animal welfare as claimed by some antagonist lobbyists.
This chapter examines the science of conscious perception and death with emphasis on synaptic transmission, consciousness, unconsciousness and death. Furthermore, various methods used in assessing unconsciousness and death are discussed as well as the different commercially available methods of stunning. An understanding of the anatomy and neurophysiology of food animals is vital to understanding pain perception during slaughter, the significance of exsanguination in promoting death and the conversion of the carcass to meat. This chapter may be useful to veterinarians, animal welfare scientists, competent authorities, abattoir workers and religious authorities who have a collective interest of protecting animal welfare during slaughter.
This scientific opinion focuses on the welfare of pigs on farm, and is based on literature and expert opinion. All pig categories were assessed: gilts and dry sows, farrowing and lactating sows, suckling piglets, weaners, rearing pigs and boars. The most relevant husbandry systems used in Europe are described. For each system, highly relevant welfare consequences were identified, as well as related animal-based measures (ABMs), and hazards leading to the welfare consequences. Moreover, measures to prevent or correct the hazards and/or mitigate the welfare consequences are recommended. Recommendations are also provided on quantitative or qualitative criteria to answer specific questions on the welfare of pigs related to tail biting and related to the European Citizen's Initiative 'End the Cage Age'. For example, the AHAW Panel recommends how to mitigate group stress when dry sows and gilts are grouped immediately after weaning or in early pregnancy. Results of a comparative qualitative assessment suggested that long-stemmed or long-cut straw, hay or haylage is the most suitable material for nest-building. A period of time will be needed for staff and animals to adapt to housing lactating sows and their piglets in farrowing pens (as opposed to crates) before achieving stable welfare outcomes. The panel recommends a minimum available space to the lactating sow to ensure piglet welfare (measured by live-born piglet mortality). Among the main risk factors for tail biting are space allowance, types of flooring, air quality, health status and diet composition, while weaning age was not associated directly with tail biting in later life. The relationship between the availability of space and growth rate, lying behaviour and tail biting in rearing pigs is quantified and presented. Finally, the panel suggests a set of ABMs to use at slaughter for monitoring on-farm welfare of cull sows and rearing pigs.
Controlled atmosphere stunning (CAS) involves exposure of animals, including poultry, to either gas mixtures or decompression and the latter is also known as low atmospheric pressure system (LAPS). Gas mixtures, especially high concentrations of carbon dioxide (CO2) in air, are widely used to stun or kill pigs and poultry, and to a limited extent some species of farmed fish. Mixtures of argon (Ar) and nitrogen (N2) are used mainly to stun or kill poultry species. Research has shown that animals exhibit aversive reactions during exposure to high concentrations of carbon dioxide or LAPS, and very little or no aversion to atmosphere containing mixtures of argon, nitrogen and low concentrations of carbon dioxide. The relative animal welfare merits of gas mixtures are presented. Decompression, or LAPS, is used to kill chickens in North America and is approved in the European Union only for killing broiler chickens weighing up to 4 kg. Experiments with killing of pigs with LAPS revealed serious welfare concern associated with hypobaric barotrauma.
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.
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.
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.
Full text pdf available from https://silsoelivestock.co.uk/?post_type=hubble_publications ------------------------------------------------------------------------------------------------------------
Low atmospheric pressure stunning (LAPS) is a slaughter technique which may be less stressful for pigs (Sus scrofa domestica) than current commercial stunning and slaughter methods. The main methods used currently for slaughtering pigs are electric and carbon dioxide stunning, both of which are widely recognised as stressful for pigs. There is currently no published research on the use of LAPS for stunning adult pigs, however there is a significant body of relevant experience from investigations into the effects of low pressure and hypoxia on humans, hypoxia for killing pigs and the use of LAPS for killing poultry, rats and piglets. In this paper, the basic physics and biology of LAPS is briefly reviewed and relevant experience from research with humans, poultry, rats and piglets is presented. On the basis of this information, some initial parameters for LAPS trials with pigs are proposed, potential welfare issues identified and an approach to achieving LAPS at a commercially viable speed is outlined. While the effects of LAPS on pigs is, at present, uncertain, the evidence from research with humans and other animals suggests that healthy, fasted pigs undergoing LAPS are unlikely to suffer from air hunger or from pain. Any pigs suffering from upper respiratory tract disease, tooth decay or excess gas in the alimentary canal may, however, experience pain. A total killing cycle is likely to require 9 to 14 min. To implement LAPS in a commercial, high throughput processing plant will require the use of multiple decompression cylinders. The evidence available suggests that LAPS could be commercially viable for pig slaughter and that for most pigs it will be less stressful than current commercial slaughter methods.
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.
In 1965 the Brambell Commission was formed to determine what components are essential to ensuring animal welfare in livestock species. In 1979, the Farm Animal Welfare Council revised the Brambell Commission recommendations and created the “five freedoms.” The “five freedoms” serve as the basis for many of the livestock welfare educational, assessment, and third‐party auditing programs and regulations globally. The five freedoms include the critical aspects of biological functioning, nature‐based measures, and affective states. When a veterinarian is assessing animal welfare, they will seek to determine if it is exhibiting normal behaviors. It is necessary to have a concept of what behaviors a feral or wild pig may choose to engage in and how this may be relevant to the domesticated pig. While the stress response is essential for animal survival and biological function, it can antagonize swine production goals such as feed efficiency, growth, carcass quality, and welfare.
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.
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.
The objectives of this research were to evaluate the effect of age and delivering method during carbon dioxide (CO2) euthanasia on the welfare of pigs (Sus scrofa). In Experiment 1, pigs aged 1, 2, 3, 4, 5 and 6 weeks (GRAD; n = 5 pigs per age) were placed in a chamber gradually filled with CO2 released at a flow rate of 20% chamber volume per min. In Experiment 2, three week old pigs were placed in a chamber pre-filled with 100% CO2 (PRE; n = 5). In both experiments, plasma cortisol concentrations were measured before and after exposure to CO2. Behaviours indicative of stress and insensibility were recorded continuously during gas exposure; panting, open-mouth breathing, righting response, escape attempts, loss of posture, muscular excitation and respiratory arrest. Cortisol concentrations were elevated in pigs after CO2 euthanasia, regardless of age or gas delivery method. The behavioural response to CO2 was not affected by pig age. Latency to display panting, righting response, escape attempts, loss of posture, muscular excitation and respiratory arrest were shorter for PRE than GRAD pigs, but, duration of escape attempts and the cortisol response to euthanasia were similar between PRE and GRAD pigs. However, pigs placed in a chamber pre-filled with CO2 spent a greater proportion of time prior to loss of posture displaying escape attempts. Regardless of age or induction method, exposure to CO2 causes behavioural changes indicative of stress prior to loss of consciousness, therefore there is a need to continue to evaluate alternative methods of euthanasia. © 2017 Universities Federation for Animal Welfare The Old School, Brewhouse Hill, Wheathampstead.
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.
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.
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
- Mohan Raj
- A B Audsley
- A 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
- R Hoenderken
- J G Van Logtestjin
- Sybesma Wand Spanjaard
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
- A Forslid
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 B Audsley
- 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
Kohlendioxid-Betaubung von Schlachtschweinen
- Hoenderken
Pre-slaughter CO2-anaesthesia in swine-NeurophysioIogical and ethical aspects
- A Forslid
Effect of CO2 on man
- Gregory