Article

Aversion to carbon dioxide stunning in pigs: Effect of carbon dioxide concentration and halothane genotype

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Abstract

Aversion to the dip-lift stunning system and to the inhalation of 70 and 90% carbon dioxide was assessed in 18 halothane-free (NN) and 14 heterozygous halothane (Nn) slaughter weight pigs using aversion learning techniques and behavioural studies in an experimental slaughterhouse. Pigs were subjected to the treatments individually. When the dip lift system contained atmospheric air, the proportion of pigs that entered the crate voluntarily increased on subsequent days, indicating that pigs habituate to the stunning system. Based on the number of attempted retreats, for the first descent into the well with atmospheric air, Nn pigs were more reactive than NN pigs. On repeating the descent, Nn pigs showed greater habituation to the procedure. When the pit contained (either 70 or 90%) carbon dioxide, the time taken to enter the crate and the incidence of pigs that attempted to retreat increased on subsequent days, indicating aversion to the carbon dioxide concentrations. The aversion was higher when the stunning system contained 90 as opposed to 70% carbon dioxide due possibly to increased irritation of the nasal mucosal membranes and more severe hyperventilation. Conversely, a decrease in the concentration of carbon dioxide increased the time to loss of posture and, therefore, lengthened the perception of the aversive stimulus till the animal lost consciousness. These results suggest that stunning with carbon dioxide is not free from pain or distress. The degree of aversion depends on the carbon dioxide concentration. Therefore, if higher concentrations of carbon dioxide are recommended for rapid induction of anaesthesia, it needs to be assumed that this may be more aversive to pigs.

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... It is known that when pigs are confronted with an unpleasant situation, such as the CO 2 stunning procedure, the first reaction is to back away (Dodman, 1977). Although no differences among diets and genotypes were found, the presence of retreat and escape attempts indicated aversion to the exposure of a high concentration of CO 2 (Raj & Gregory, 1995;Velarde et al., 2007). Furthermore, although gasping is not considered an expression of aversion, it may compromise animal welfare as it is a physiological reaction associated with breathlessness during the inhalation of the gas (Raj & Gregory 1996;Lambooij et al. 1999). ...
... Furthermore, although gasping is not considered an expression of aversion, it may compromise animal welfare as it is a physiological reaction associated with breathlessness during the inhalation of the gas (Raj & Gregory 1996;Lambooij et al. 1999). Velarde et al. (2007) stated that pigs carrying the halothane gene (Nn) were relatively more sensitive to exposure to CO 2 , showing a higher incidence of aversive behaviour than halothane negative pigs (NN). Although the present study was performed using halothane positive (nn) and free-gene halothane negative pigs (NN), no differences were observed between them. ...
... Our results indicated that the consciousness was lighter for the NN pigs than nn ones, so the probability of recovery from unconsciousness before death was higher in NN than in nn. In agreement with our results, Velarde et al. (2007) reported a reduction of the onset of unconsciousness in pigs containing the halothane gene (Nn) in comparison to NN. ...
Article
Sixty-one animals with different Halothane genes (homozygous halothane positive, n=34; and homozygous halothane negative, n=27) were fed with three diets (control group, with no supplement; magnesium (Mg) group with 1.28 g MgCO3/kg and tryptophan (Trp) group with 5 g l-Trp/kg) during the last 5 days before slaughter. Animals were submitted to minimal stress antemortem conditions. Pig behaviour was recorded at the experimental farm, raceway to the CO2 stunning system and during the stunning period. Corneal reflexes were recorded after stunning as well. There were no differences in feed intake among diets (P>0.05) during the 5 days of treatment. The halothane positive (nn) group had lower intake than the halothane negative (NN) group (P0.05) among treatments or halothane genotype. A significant (P
... It is generally believed that behaviors, such as heavy breathing, open-mouth breathing, squeals, and escape attempts, are signs of varying degrees of distress [6,13,14]. Importantly, it would be helpful to determine if these behaviors are also indicative of pain. In order to value one method of euthanasia over another, both pain and distress need to be assessed and alleviated. ...
... 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]. ...
... Escape attempts are considered evidence of stress or aversion in pigs during euthanasia [14,22]. In our study, pigs in the CO 2 treatment had 14 times more escape attempts than pigs in the N 2 O treatment. ...
Article
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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.
... The use of CO 2 is often recommended (AVMA, 2007). At the same time, CO 2 is criticized as being aversive to swine (Raj and Gregory, 1995;Velarde et al., 2007) and causes a profound sense of breathlessness in humans (Gregory et al., 1990). Furthermore, little is known about the reaction of neonatal piglets to CO 2 euthanasia. ...
... In Exp. 3, only compromised piglets destined to be euthanized by the Purdue University farm staff were used, with the justifi cation that this type of neonatal piglet represented the population of interest, as that is when morbidity and the need for euthanasia are greater in production settings. Piglets were not screened for their halothane genotype, which may infl uence their sensibility to gas changes (Velarde et al., 2007), although the proportion of halothane gene in this herd is expected to be low. ...
... The treatments were CO 2 (90%), N 2 O (60%) and CO 2 (30%), Ar (60%) and CO 2 (30%), and N 2 (60%) and CO 2 (30%). The treatments were chosen for these reasons: a standard recommendation for gas euthanasia is 80 to 90% CO 2 (AVMA, 2007) although it has been shown to be aversive based on previous research in mature swine (Raj and Gregory, 1995;Velarde et al., 2007). Therefore, 90% CO 2 was chosen as a basis of comparison for the aversiveness of the alternative gas mixtures. ...
Article
The search for alternative methods to euthanize piglets is critical to address the public's concern that current methods are not optimal. Scientific evidence support that blunt force trauma is humane when carried out correctly, but most people find it visually difficult to accept. The use of CO2 is often recommended, at the same time it is criticized as being aversive to pigs. This research sought to: 1) identify a method of scientifically determining if piglets find a gas aversive, using an approach-avoidance test which relies on the piglet's perspective, and 2) test different gas mixtures to determine if they are effective and humane for neonatal piglet euthanasia. Pigs were allowed to walk freely between 1 chamber filled with air and another chamber either gradually filled with gas mixtures (Experiment 1) or pre-filled with gas mixtures (Experiment 2). Experiment 1 tested CO2 (90%) and air (10%); N2O (60%) and CO2 (30%); Ar (60%) and CO2 (30%); and N2 (60%) and CO2 (30%). Since piglets had to be removed when they started to flail, the test was shortest (P < 0.01) for the pigs in the CO2 treatment compared with pigs in the N2O/CO2, Ar/CO2, and N2/CO2 treatments, 3.1 ± 0.2, 8.5 ± 0.6, 9.6 ± 0.4, and 9.9 ± 0.1 min, respectively. Nonetheless, all gas mixtures adversely affected the pigs, causing the pigs to leave the test chamber. In Experiment 2, piglets were allowed to enter a chamber pre-filled with N2/CO2 or N2O/CO2 (both 60%/30%). Pigs exposed to the pre-fill chambers started to flail in less than 20 s, much faster in comparison to the gradual fill method, which support that this method was more aversive. In Experiment 3, piglets were euthanized using a 2-step procedure. Pigs were first placed in a gradual fill chamber with 1 of 4 gas mixtures: 90% CO2, N2/CO2, N2O/CO2 or N2O/O2 (the last 3 mixtures at 60%/30%) followed by placement into a 90% CO2 pre-fill chamber when the pigs started to flail or were anesthetized. All 3 gas treatments that contained CO2 killed pigs more quickly than N2O/O2 (P < 0.05). However, N2O/O2 was the only treatment that anesthetized the pigs instead of causing squeals or flailing, although requiring about 12 min longer. Although longer, a 2-step procedure in which pigs are anesthetized with a mixture of N2O and O2 prior to being euthanized by immersion in CO2 may prove to be more humane than CO2 alone.
... In this study, the euthanasia process was separated into 2 phases, conscious and unconscious. In the present study, the transition from conscious to unconscious was determined by loss of posture, which has been identified in previous research as an indicator for loss of consciousness (Forslid, 1987;Raj and Gregory, 1996;Velarde et al., 2007). However, there is a transition phase before loss of posture during which a number of behaviors are typically observed, including open-mouth breathing, ataxia, and righting response. ...
... Behaviors chosen for welfare assessment included those associated with physiological distress, such as open-mouth breathing (Forslid, 1987;Martoft et al., 2002;Mota-Rojas et al., 2012), and psychological distress, such as escape (Blackshaw et al., 1988;Velarde et al., 2007), righting response (Grandin, 1998;Kohler et al., 1999;American Veterinary Medical Association [AVMA], 2013), defecation, and urination. Once unconscious, the point of interest shifted from welfare to efficacy; it is vital that the process be practical for on-farm implementation. ...
... There is evidence of capacity for direct sensation and perception of CO 2 gas though the trigeminal nerve in rats (Anton et al., 1991), humans (Anton et al., 1992), and chickens (McKeegan et al., 2005), but this has not been examined in pigs. Open-mouth breathing is a physiological reaction associated with dyspnea (Burki and Lee, 2010) and has been identified as an indicator of compromised welfare in the pig (Velarde et al., 2007). It is important to note other researchers have used hyperventilating (Martoft et al., 2002), respiratory distress (Raj and Gregory, 1996), and gasping (Rodríguez et al., 2008) when describing this behavior. ...
Article
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The objectives of this study were to assess efficacy and welfare implications of gas euthanasia when applied to weaned and neonate pigs. Parameters associated with welfare, which were measured before loss of consciousness, included open-mouth breathing, ataxia, righting response, and escape attempts. Two age groups (weaned and neonate) were assessed in 9 gas treatments arranged in a 2 × 4 factorial design, with 2 gas types (CO2 = 100% CO2 and 50:50 = 50:50 CO2:argon) and 4 flow rates (box volume exchange/min: slow = 20%; medium = 35%; fast = 50%; prefill = prefilled followed by 20%) and a control treatment in which ambient air was passed through the box. Pig pairs (10/treatment) were placed in a modified Euthanex AgPro system (Euthanex Corp., Palmer, PA). Behavioral and physiological responses were observed directly and from video recordings for latency, duration, prevalence (percent of pigs affected), and frequency (number of occurrences/pig). Data were analyzed as linear mixed models or with a Cox proportional hazard model as appropriate. Piglet pair was the experimental unit. For the weaned pig, welfare was superior with CO2 relative to 50:50 within 1 or more flow rates on the basis of reduced duration of open-mouth breathing, duration of ataxia, frequency of escape attempts, and duration and frequency of righting response (P < 0.05). No measured parameters indicated superior welfare with the use of 50:50, whereas latencies to loss of posture and last movement favored CO2 (P < 0.05). Faster flow rates were associated with reduced (P < 0.05) duration or frequency of open-mouth breathing, ataxia, and righting response, as well as superior (P < 0.05) indicators of efficacy, including latencies to loss of posture, gasping, and last movement, relative to slower flow rates. Weaned pigs were more likely to defecate (P < 0.01), display nasal discharge (P < 0.05), and display longer (P < 0.001) latencies to loss of posture and last movement than neonates. Duration of ataxia was the only parameter for which neonates were superior (P < 0.01) to weaned pigs during euthanasia. As such, a 50:50 CO2:argon gas mixture and slower flow rates should be avoided when euthanizing weaned or neonate pigs with gas methods. Neonate pigs succumb to the effects of gas euthanasia quicker than weaned pigs and display fewer signs of distress.
... No obstante, signos de aversión, como 'intentos de retirada' o 'escape' han sido reportados en cerdos durante el aturdimiento con CO 2 (Velarde et al., 2007), y sobre todo, demerita el bienestar de estos 5 segundos antes de completar un estado de anestesia . Es un hecho que éste tipo de comportamientos aversivos ya se encuentran contemplados en rastros dentro de los protocolos de aturdimiento con CO 2 . ...
... I Echado + § (Sadler et al., 2014b). II Intentos de escape + Respuesta aversiva ante altas concentraciones de CO 2 , es posiblemente debido a una alta estimulación de nociceptores al CO 2 ubicados en la mucosa nasal y en los pulmones (Velarde et al., 2007). II Cabeceo + Un 50% de cerdos expuestos a altas concentraciones de CO 2 (80-90%) muestran sacudir la cabeza y convulsiones durante la exposición al CO 2 . ...
... En relación a los resultados, al menos tres conductas están relacionados con aversión al CO 2 , tales como: 'intentos de retirada', 'pérdida de la postura', 'intentos para incorporarse' y 'contracciones musculares'. Otros estudios señalan que el uso de CO 2 bajo cualquier concentración, demerita la integridad fisiológica del cerdo permitiendo que se expresen indicadores conductuales propios de la aversión al gas, por ejemplo: 'intentos de retirada', 'intentos inspiratorios', 'pérdida de la postura', 'excitación muscular o contracciones musculares' (Dalmau et al., 2010;Llonch, 2012a,b), 'convulsiones', 'cerdos sentados' (Gerritzen et al., 2008), 'intentos de escape' (Velarde et al., 2007), 'salivación', 'defecación', 'vómito' (Sadler et al., 2014b), y 'saltos violentos' (Deiss et al., 2006, Terlouw et al., 2008. ...
Thesis
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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.
... No obstante, signos de aversión, como 'intentos de retirada' o 'escape' han sido reportados en cerdos durante el aturdimiento con CO 2 (Velarde et al., 2007), y sobre todo, demerita el bienestar de estos 5 segundos antes de completar un estado de anestesia . Es un hecho que éste tipo de comportamientos aversivos ya se encuentran contemplados en rastros dentro de los protocolos de aturdimiento con CO 2 . ...
... I Echado + § (Sadler et al., 2014b). II Intentos de escape + Respuesta aversiva ante altas concentraciones de CO 2 , es posiblemente debido a una alta estimulación de nociceptores al CO 2 ubicados en la mucosa nasal y en los pulmones (Velarde et al., 2007). II Cabeceo + Un 50% de cerdos expuestos a altas concentraciones de CO 2 (80-90%) muestran sacudir la cabeza y convulsiones durante la exposición al CO 2 . ...
... En relación a los resultados, al menos tres conductas están relacionados con aversión al CO 2 , tales como: 'intentos de retirada', 'pérdida de la postura', 'intentos para incorporarse' y 'contracciones musculares'. Otros estudios señalan que el uso de CO 2 bajo cualquier concentración, demerita la integridad fisiológica del cerdo permitiendo que se expresen indicadores conductuales propios de la aversión al gas, por ejemplo: 'intentos de retirada', 'intentos inspiratorios', 'pérdida de la postura', 'excitación muscular o contracciones musculares' (Dalmau et al., 2010;Llonch, 2012a,b), 'convulsiones', 'cerdos sentados' (Gerritzen et al., 2008), 'intentos de escape' (Velarde et al., 2007), 'salivación', 'defecación', 'vómito' (Sadler et al., 2014b), y 'saltos violentos' (Deiss et al., 2006, Terlouw et al., 2008. ...
... These reactions include convulsions (apparently involuntary muscle contractions), avoidance behaviours and difficult breathing (Forslid 1987;Dodman, 1977;Gerritzen et al., 2004). In pigs, the respiratory changes occur within seconds of immersion in CO 2 (Forslid 1987;Velarde et al., 2007). The aversive nature has been confirmed in humans, in whom CO 2 inhalation causes pain and a sensation of discomfort that increases with the concentration (Danneman et al., 1997;Hari et al., 1997;Hummel and Livermore, 2002). ...
... In this study, time to loss of the standing posture has not been evaluated (Box 5). In another study, 20% of the pigs showed muscle contractions before the loss of posture, 20% at the moment of loss of posture and 10 % thereafter (Velarde et al., 2007). Overall, the presence or not of involuntary muscle contractions before, during and after the loss of consciousness seems to differ between studies suggesting that their appearance may be context or animal dependent. ...
... Overall, the presence or not of involuntary muscle contractions before, during and after the loss of consciousness seems to differ between studies suggesting that their appearance may be context or animal dependent. For example, pig breeds differ in their reactions to exposure to CO 2 , which could partly explain the observed differences (Grandin, 1992;Channon et al., 2000;Velarde et al., 2007). This underlines the importance of taking into account the genetic type and individual differences when studying the sequential order of effects of CO 2 inhalation. ...
... However, it has been recognized that CO 2 gas at high concentration is acidic and can cause distress in pigs, mainly through irritation in the nasal mucosal membranes and lungs (Peppel & Anton, 1993). It also has been shown that carbon dioxide induces severe respiratory distress and a sense of breathlessness (Gregory, Raj, Audsley, & Daly, 1990;Velarde et al., 2007). ...
... Several studies have assessed the time to unconsciousness in experimental settings (e.g. (Llonch, Dalmau, Rodriguez, Manteca, & Velarde, 2012;Velarde et al., 2007;Verhoeven, Gerritzen, Velarde, Hellebrekers, & Kemp, 2016)), but only a few have studied conditions during routine slaughter (Atkinson, Larsen, Llonch, Velarde, & Algers, 2015). Furthermore, no studies have evaluated the stunning of sows under commercial conditions. ...
... An ethogram of all behaviors assessed within the framework of this study is available in Table S1. 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. ...
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.
... The CO 2 stunning method involves lowering groups of pigs in a gondola into a well that is pre-filled with a high concentration of CO 2 . According to European legislation, the CO 2 concentration should at least be 80%, but many slaughterhouses use 90% CO 2 or higher in attempts to increase throughput at the slaughter plant (Velarde et al., 2007;Council Regulation (EC) 1009, 2009). Rapid and deeper respiration induced by higher CO 2 concentrations increases the intake of CO 2 that shortens the induction period and time to loss of consciousness (Forslid, 1992). ...
... (Velarde et al., 2000;EFSA, 2004). Before pigs lose consciousness, however, behaviour including excitement, retreat and escape attempts and respiratory changes (gasping) have been observed (Raj andGregory, 1995 and1996;Velarde et al., 2007;Terlouw et al., 2016). 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 (Manning and Schwartzstein, 1995;Raj, 2006). ...
... While changes in breathing pattern are generally associated with aversion, there is little consensus concerning the interpretation of the occurrence of convulsions or (involuntary) muscle contractions (Terlouw et al., 2016b). These muscle contractions have been observed both before (Velarde et al., 2007;Rodriguez et al., 2008) and after loss of consciousness (Hoenderken, 1983;Forslid, 1987;Velarde et al., 2007). The objective of the current study was to assess the relationship between behavioural measurements and onset of unconsciousness as identified by EEG activity during 80% CO 2 (80C) or 95% CO 2 (95C) stunning in pigs. ...
... Several gases are currently used to euthanise, stun or kill animals, including CO 2 and the inert gases, argon (Ar) and nitrogen [10][11][12][13]. Gaseous methods are routinely used for laboratory rodents, with CO 2 being the most commonly used agent because it is heavier than air and thus containable, cheap to obtain and relatively safe for human operators [14][15][16][17]. ...
... Gaseous methods are routinely used for laboratory rodents, with CO 2 being the most commonly used agent because it is heavier than air and thus containable, cheap to obtain and relatively safe for human operators [14][15][16][17]. The use of CO 2 is also common for stunning pigs in slaughter plants in the US and Europe [13]. High concentrations of CO 2 cause central nervous system depression leading to loss of consciousness and subsequent death. ...
... In contrast, 100% Ar appeared to have the least impact on welfare of the gas treatments. Escape behaviours, such as retreating, raising the forelegs against the sides of the chamber, and running or charging at the walls or lid of the chamber are considered evidence of stress or aversion in pigs exposed to hypoxic or hypercapnic atmospheres [13,24,32]. Escape behaviours were observed in response to all three gas treatments, but occurred sooner and for a longer duration in piglets exposed to 100% CO 2 than in those exposed to 100% Ar. ...
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.
... The CO2 stunning method involves lowering groups of pigs in a gondola into a well that is pre-filled with a high concentration of CO2. According to European legislation, the CO2 concentration should at least be 80%, but many slaughterhouses use 90% CO2 or higher in attempts to increase throughput at the slaughter plant (2,3). Rapid and deeper respiration induced by higher CO2 concentrations increases the intake of CO2 that shortens the induction period and time to loss of consciousness (4). ...
... 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). ...
... While changes in breathing pattern are generally associated with aversion, there is little consensus concerning the interpretation of the occurrence of convulsions or (involuntary) muscle contractions (13). These muscle contractions have been observed both before (3,9) and after loss of consciousness (3,23,24). The objective of the current study was to assess the relationship between behavioral measurements and onset of unconsciousness as identified by EEG activity during 80% CO2 (80C) or 95% CO2 (95C) stunning in pigs. ...
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.
... maintaining balance during transport). In pigs, lying behaviour is an important tool within behavioural thermoregulation, and therefore related to the EET (Velarde et al., 2007). Combining measurements of pigs' energy metabolism and animal behaviour has shown that the thermal neutral or comfort behaviour for pigs occurs when they are lying on their side and touching each other. ...
... In the presence of normal atmospheric air (absence of a high CO 2 concentration), the process of entering the cage and pigs being lowered into the pit or moved within the tunnel does not cause aversion (Velarde et al., 2007;Dalmau et al., 2010). Two main systems exist, the dip-lift system and the paternoster system. ...
... Pigs are immersed into a concentration gradient of the gas, such that, as the cage is lowered into the pit, the CO 2 concentration continues to rise until it reaches 80-90% at the bottom of the well (EFSA, 2004). Under commercial conditions, the concentration of CO 2 should be at least 80%, but more and more slaughterhouse use 90% or higher in an attempt to increase throughput rates (Velarde et al., 2007) and guarantee effective stun duration. ...
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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.
... CO2 stunning allows for pigs to be handled and stunned in small groups instead of individually, with minimized human-animal contact and reduced stress related to separation from conspecifics [3,4]. 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 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. ...
... Pigs exposed to high-concentration N2 gas in foam showed no gasping, which is considered an indicator of the onset of breathlessness [5] and is one of the well documented aversive responses to high concentration CO2 gas [6,17]. These results are in line with previous studies, which have shown that exposure to inert gases or mixtures with low CO2 concentrations reduces gasping in pigs before loss of consciousness compared to high concentrations of CO2 [11,18]. ...
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.
... This can reduce pre-slaughter handling stress in comparison to moving pigs in a single file and possibly using a restraining device (EFSA, 2004). The main disadvantage of CO 2 stunning is that it does not induce instantaneous insensibility, and exposure to CO 2 at concentrations high enough to induce insensibility has been shown to be aversive to pigs (Raj and Gregory, 1995;Velarde et al., 2007). There is also variation between individual pigs in the reaction to CO 2 , from no observable reaction to vocalisations and violent attempts to escape (EFSA, 2020). ...
... Gasping was relatively common, occurring in 63-82% of the pigs observed, respectively, and with little variation between abattoirs. Gasping is considered to occur at the onset of breathlessness (Velarde et al., 2007), and CO 2 is likely to lead to severe air hunger, which is reported to be the most unpleasant sensation of breathlessness (Beausoleil and Mellor, 2015). However, gasping has also been reported to persist beyond isoelectric EEG, and therefore may not necessarily be indicative of consciousness (Rault et al., 2020). ...
... Loss of posture is considered the first indicator of loss of consciousness (Raj andGregory, 1995, 1996;Velarde et al., 2007;Llonch et al., 2012) and is characterized by the inability of the animal to remain in a standing position. In the present study, pigs lost posture on average within 22.5 s of the time the gondola started lowering down, which is in accordance with the literature ( (Raj, 1999): 17 s at 90% CO 2 ; Velarde et al., 2007: 22.4 s at 80% CO 2; Verhoeven et al., 2016: 37 s at 80% and 23 s at 95%). ...
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.
... 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. ...
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.
... Allowing pigs to remain in groups during preslaughter handling and stunning also respects the natural herd instincts in pigs to remain in social contact with one another, thereby minimizing fear and stress caused by isolation and close human contact, often associated with electrical stunning. Close human contact and restraint of pigs individually during stunning has been associated with causing preslaughter handling stress and meat quality defects, such as pale, soft, and exudative (PSE) and blood splash [1,2]. ...
... The main animal welfare concern is that hypercapnia produces irritation of the nasal mucosal membranes, hyperventilation, and breathlessness (perceived as a sense of lack of air) [5,6]. 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. ...
... Llonch et al. [16] tested aversion responses in pigs exposed to a range of mixtures during stunning containing 15 to 30% CO 2 in a N 2 saturated atmosphere. Pigs showed behaviors that indicated the less aversive concentration of hypercapnic-hypoxia contained 80% N 2 and 20% CO 2 , which in that study as well as in other references from Llonch and colleagues was designated as 80N20C. However, in the present study, hypercapnic-hypoxia is referred to as 20C2O. ...
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.
... The justification of using this age is that this type of piglet represents the population of interest, as this is when morbidity and the need for euthanasia is greater in production settings. Piglets were not screened for their halothane genotype, which may influence their sensibility to gas changes [7], although the proportion of halothane gene in this herd is expected to be very low. An attempt was made to use only one piglet per sow to avoid bias; however, when two piglets were euthanized from the same sow they were subject to different treatments. ...
... More squeals may indicate an increased level of agitation, fear, or distress. Escape attempts and righting responses are also associated with distress [7,8]. Righting responses suggest an awareness of being physically impaired and can be distressing [18]. ...
Article
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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.
... Tonic seizures are followed by clonic seizures, which manifest as kicking or galloping movements (Berghaus and Troeger, 1998;Gregory, 1998). These convulsive movements will change to (Raj and Gregory, 1996;EFSA, 2004) Hyperventilation Excessive rate and depth of breathing (Raj and Gregory, 1996;EFSA, 2004) Head shaking Rapid shaking of the head, most times accompanied by stretching and/or withdrawal movements of the head (EFSA, 2004;Velarde et al., 2007) Figure 3: Two-step electrical killing with head-only application followed by ventricular fibrillation (source: DEFRA, 2003) paddling movements and relaxation and loss of muscle tone recognised by drooping ears and limp legs (EFSA AHAW Panel, 2013). Reflexes that would require brain control are also abolished. ...
... During exposure to gas mixtures, ABMs related to pain, fear and respiratory distress are head shaking, laboured breathing (gasping), escape attempts and high-pitched vocalisations (Raj and Gregory, 1996;Velarde et al., 2007;Terlouw et al., 2016;O'Malley et al., 2018). However, during the killing procedure, especially during killing for disease control, observations during containerised gassing are difficult or even not possible. ...
Article
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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.
... However, most people find it visually difficult to accept and it can be emotionally disturbing for the person conducting the act. Carbon dioxide (CO 2 ) chambers have been widely adopted as an alternative, but CO 2 has received criticism as being aversive to swine [5][6][7], hence the search for a method of on-farm euthanasia that is humane, practical, economical and socially acceptable. ...
... Female piglets from Yorkshire × Landrace dams bred to Duroc × Hampshire sires were used, with no apparent health issues and visually well-fed. Piglets were not screened for their halothane genotype, which may influence their sensibility to gas changes [6], although the proportion of halothane gene in this herd is expected to be low because the farm has generated all of its replacement females for the last 10 years and all purchased sires have been blood tested and negative for the halothane gene. Experiments 1 and 2 used an approach-avoidance test developed and validated previously [7], and were performed in the same facilities as these previous experiments. ...
... In general, stunning with carbon dioxide is not considered a welfare friendly method, as this gas has side-effects for pigs (Velarde et al., 2007;Becerril-Herrera et al., 2009). In particular, Velarde et al. (2007) found that the degree of aversion is positively correlated with the carbon dioxide concentration. ...
... In general, stunning with carbon dioxide is not considered a welfare friendly method, as this gas has side-effects for pigs (Velarde et al., 2007;Becerril-Herrera et al., 2009). In particular, Velarde et al. (2007) found that the degree of aversion is positively correlated with the carbon dioxide concentration. Conversely, a decrease in the concentration increases the time to loss of consciousness. ...
... However, most people find it visually difficult to accept and it can be emotionally disturbing for the person conducting the act. Carbon dioxide (CO 2 ) chambers have been widely adopted as an alternative, but CO 2 has received criticism as being aversive to swine [5][6][7], hence the search for a method of on-farm euthanasia that is humane, practical, economical and socially acceptable. ...
... Female piglets from Yorkshire × Landrace dams bred to Duroc × Hampshire sires were used, with no apparent health issues and visually well-fed. Piglets were not screened for their halothane genotype, which may influence their sensibility to gas changes [6], although the proportion of halothane gene in this herd is expected to be low because the farm has generated all of its replacement females for the last 10 years and all purchased sires have been blood tested and negative for the halothane gene. Experiments 1 and 2 used an approach-avoidance test developed and validated previously [7], and were performed in the same facilities as these previous experiments. ...
... However, the use of carbon dioxide to stun rabbits for meat consumption is not allowed in the EU (Regulation 1009/2009) because of its aversion in other species, such as mice, rats or swine (Raj & Gregory 1995;Smith and Harrap, 1997;Leach et al., 2002;Conlee et al., 2005;Velarde et al., 2007;Dalmau et al., 2010a). Inhalation of CO 2 at high concentrations causes irritation of the nasal mucosal membranes and lungs in rats (Peppel & Anton, 1993), where the presence of chemoceptors acutely sensitive to this gas has been described (Manning & Schwartzstein, 1995). ...
... In all cases, before loss of posture, animals showed aversion to the gas, (vocalisations and nasal discomfort), behaviours not seen when the animals were exposed to atmospheric air. These behaviours are comparable to those studied in pigs as signs of aversion, such as vocalisations, retreat or escape attempts and gasping (Dodman, 1977;Raj and Gregory, 1996;Velarde et al., 2007;Rodriguez et al., 2008;Dalmau et al., 2010a;Llonch et al., 2012b), where high CO 2 concentrations are also used for stunning. Moreover, the time until loss of posture appears in pigs is also similar to that in rabbits, around 30s (Raj and Gregory, 1996;Llonch et al., 2012b). ...
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.
... Dit syndroom wordt gerelateerd aan verschillende symptomen, waaronder beven, spiercontracties en een verhoogde lichaamstemperatuur. PSS kan door de inhalatie van halothaan worden uitgelokt (Geers et al., 1992;Velarde et al., 2007). ...
Article
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De castratie van biggen staat bekend als een belangrijk economisch en welzijnsprobleem in de huidige varkenshouderij. De Belgische varkenssector staat onder druk om op korte termijn oplossingen voor dit dierenwelzijnprobleem te vinden. Een mogelijk alternatief is het castreren van biggen onder verdoving om de pijn tijdens de castratie te verminderen. Ook de berengeur in vlees kan er door gereduceerd worden, en het dierenwelzijn en de arbeidsomstandigheden kunnen er door verbeterd worden. Bovendien worden andere potentiële technieken om castratie te beperken, verder onderzocht. Bij castratie onder verdoving wordt de pijn tijdens de castratie weggenomen, maar analgetica blijven noodzakelijk voor de behandeling van napijnen.
... One area worth mentioning here that did not turn up in this search is the possibility of genetic differences in the response of pigs to CO 2 . Some pigs seem to have a calm induction to high-concentration CO 2 , while others have agitated responses with repeated escape attempts (Grandin, 1988;Velarde et al., 2007). Limited research has been done on this area, and genomic methods should be used to determine if specific genetic types do have milder reactions to high concentrations of CO 2 . ...
Article
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Using carbon dioxide (CO 2) for stunning pigs at slaughter is common in Europe. The use of group stunning is a major advantage with CO 2 , which is done without restraining the pigs and with minimized human contact. However , high concentrations of CO 2 have been known for decades to cause pain, fear and distress in pigs before loss of consciousness, and the stunning method is clearly associated with animal welfare concerns. This study reviewed the scientific literature to find recent developments or evaluations of alternative methods that could lead to the replacement of CO 2 for stunning pigs at slaughter. Potential alternative methods found in the literature were described and then assessed to identify specific research and development needs for their further development. Only 15 empirical studies were found in the search of peer-reviewed literature since 2004, which is less than one per year. Furthermore, half of the studies focused on evaluating methods to improve high-concentration CO 2 stunning rather than an alternative to CO 2. Since no clear alternative has emerged, nor a method to improve CO 2 stunning, there is obviously a strong need to focus research and development to find solutions for improving animal welfare when stunning pigs at slaughter.
... The day of slaughter consists of a chain of potential stressors such as regrouping and housing in pick-up facilities (a separate housing unit designed to obtain maximum protection against disease), loading, transport including stops during the journey, unloading, regrouping and housing in the lairage, stunning and killing (Barton Gade, 2004). Previous studies have investigated the effect of single potential stressors within this chain, such as repeated regrouping (Coutellier et al., 2007), handling during moving (Correa et al., 2010;Edwards et al., 2010b), exposure to an unknown environment Meat Science 103 (2015) 13-23 (Lewis, Hulbert, & McGlone, 2008), high stocking density (Warriss, 1998), high ambient temperature (Sutherland, McDonald, & McGlone, 2009) or CO 2 concentration at stunning (Nowak, Mueffling, & Hartung, 2007;Velarde et al., 2007). However, so far no animal welfare assessment approach has considered the accumulated effects of the different potential stressors pigs encounter from the pick-up facilities at the farm until killing at the slaughterhouse. ...
Article
Animal welfare on the day of slaughter is of increasing concern to the authorities and consumers alike, creating a need not only to optimize the welfare of the animals but also to document the level of welfare. The day of slaughter is composed of a variety of stages, initiated when the pigs leave the home pen and including pick-up facilities, transport, lairage, stunning and sticking. At each of these stages, the animals are exposed to different stressors that, both individually and in interaction with one another, can compromise welfare. As part of the initial work aiming to document the welfare of finishing pigs on the day of slaughter, this paper provides an overview of the individual stages including a discussion of potential stressors and potential welfare measurements. These measurements are discussed with regard to their relevance and suitability for documentation of animal welfare on the day of slaughter for development of on-site tools for continuous automatic monitoring of animal welfare.
... Carbon dioxide, being an acidic gas, is pungent to inhale both in high and low concentrations (B70% and 80%) and provokes aversion in pigs (Raj andGregory 1995, 1996). Recently, Velarde et al. (2007) reported that aversion was higher at 90 than at 70% CO 2 , possibly due to higher irritation of the nasal mucosa membranes and more severe hyperventilation. However, 90% CO 2 induced anaesthesia faster, as shown by the reduced latency to lose posture. ...
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.
... In the animals with genetic predisposition for myopathy a rapid course of glycogenolysis is initiated during slaughter, which leads to the accumulation of lactic acid in muscles and thus to a rapid decline in pH value [Koćwin--Podsiadła, 1998]. Velarde et al. [2007] in their comparative studies on the aversive response of livestock with a negative halothane reaction and of heterozygotes with the positive reaction stunned with CO 2 , observed that when the stunning chamber was filled with 90% carbon dioxide the pigs needed statistically significantly more time to enter the stunning gondola than these stunned with 70% CO 2 . In the case of stunning with 90% CO 2 , the number of animals trying to escape was twofold higher (77%) as compared to the stunning with CO 2 used in 70% concentration (36%). ...
Article
The aim of the study was to analyse the effect of CO2 concentration in pharmacological stunning method of pigs on selected quality traits of meat. Investigations were carried out on 200 fatteners of mass population. Half the animals (n=100) were stunned with 92% and the other 100 fatteners were stunned with 88% CO2. The stunning effectiveness was evaluated by observing animals' response to CO2 concentration. In the group of the fatteners stunned with 92% CO2, all animals were stunned correctly, whereas in the group of the fatteners stunned with a lower concentration of CO2 (88%), the percentage of ineffectively stunned animals reached 17%. A statistically significant (p≤0.01) influence of carbon dioxide concentration in the pharmacological stunning method was noticed on pH24, lightness of meat - L* (p≤0.05) and b* value. A higher frequency of carcasses with PSE and DFD was observed among the fatteners stunned with 92% CO2 (respectively 16% and 7% vs. 9% and 1% reported for animals stunned with 88% CO2). © Copyright by Institute of Animal Reproduction and Food Research of the Polish Academy of Sciences.
... In both methods, exposure of pigs with normal respiration to a constant supply of 80% to 90% CO 2 for a minimum of 5 minutes is necessary for effective euthanasia. 211,214,251,[512][513][514][515][516][517][518] Carbon dioxide offers advantages for euthanasia, including that it is relatively inexpensive, nonflammable and nonexplosive, and clean (no blood loss). Drawbacks to the use of CO 2 are that it requires special equipment and training for efficient and safe application, and that there is little published research on appropriate techniques for euthanizing young (neonatal and growing) pigs. ...
... Dit syndroom wordt gerelateerd aan verschillende symptomen, waaronder beven, spiercontracties en een verhoogde lichaamstemperatuur. PSS kan door de inhalatie van halothaan worden uitgelokt (Geers et al., 1992;Velarde et al., 2007). ...
Article
De castratie van biggen staat bekend als een belangrijk economisch en welzijnsprobleem in de huidige varkenshouderij. De Belgische varkenssector staat onder druk om op korte termijn oplossingen voor dit dierenwelzijnprobleem te vinden. Een mogelijk alternatief is het castreren van biggen onder verdoving om de pijn tijdens de castratie te verminderen. Ook de berengeur in vlees kan er door gereduceerd worden, en het dierenwelzijn en de arbeidsomstandigheden kunnen er door verbeterd worden. Bovendien worden andere potentiële technieken om castratie te beperken, verder onderzocht. Bij castratie onder verdoving wordt de pijn tijdens de castratie weggenomen, maar analgetica blijven noodzakelijk voor de behandeling van napijnen.
... During movement to the stunner, the number of slipping or falling pigs (%) was counted. The CO 2 concentration (%) of the gas stunning was recorded and the stunning efficiency was evaluated by the corneal reflex method (Van de Perre, Ceustermans, Leyten, & Geers, 2010;Velarde et al., 2007). All pigs in this study were effectively stunned. ...
Article
This study investigates the relationship between sound levels, pre-slaughter handling during loading and pork quality. Pre-slaughter variables were investigated from loading till slaughter. A total of 3213 pigs were measured 30 min post-mortem for pH30LT (M. longissimus thoracis). First, a sound level model for the risk to develop PSE meat was established. The difference in maximum and mean sound level during loading, mean sound level during lairage and mean sound level prior to stunning remained significant within the model. This indicated that sound levels during loading had a significant added value to former sound models. Moreover, this study completed the global classification checklist (Vermeulen et al., 2015a) by developing a linear mixed model for pH30LT and PSE prevalence, with the difference in maximum and mean sound level measured during loading, the feed withdrawal period and the difference in temperature during loading and lairage. Hence, this study provided new insights over previous research where loading procedures were not included.
... Based on a previous experiment [20], we did not expect sex differences in response to the gasses but selected females to minimize potential variability in responses. Piglets were not screened for halothane genotype, which may influence their sensibility to gas changes [21], although the proportion of the halothane gene in Australian herds is expected to be low. The piglets were individually housed in 1.5 × 0.75 m pens, with a feeder in front and a nipple drinker on the side of the pen and fed ad libitum a commercial concentrated weaning diet. ...
Article
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Consciousness is central to animal welfare concerns. Its assessment is most often conducted based on behavior, with a poor understanding of the correspondence between behavior and the neurobiological processes that underlie the subjective experience of consciousness. Recording of brain electrical activity using electrodes placed under the skull improves EEG recording by minimizing artifacts from muscular or cardiac activities, and it can now be combined with wireless recording in free-moving animals. This experiment investigated the correspondence between wireless ‘under the skull’ epidural EEG and the behavior of 18 five-week-old female piglets undergoing nitrous oxide (N2O) or carbon dioxide (CO2) gradual fill gas euthanasia at 25% replacement rate per minute of the chamber volume. Piglets exposed to CO2 had a peak in EEG total power (‘Ptot’) during the flailing stage, whereas piglets exposed to N2O had a higher EEG 95% spectral edge frequency (‘F95’) during their initial explorative behavior phase and a drop in EEG median frequency (‘F50’) after loss of posture. Loss of posture without righting attempt, as the last behavioral state observed during euthanasia, preceded the onset of transitional EEG on average 0.9 and 3.1 min (for CO2 and N2O treatments, respectively), and the onset of isoelectric EEG by 4.5 and 6.2 min (for CO2 and N2O treatments, respectively). Paddling movements occurred shortly before and during transitional EEG but never during isoelectric EEG, whereas gasps persisted after the EEG had become isoelectric. The dynamics of EEG spectral changes were complex to interpret in relation to the degree of consciousness, but isoelectric EEG as an unequivocal indicator of unconsciousness appeared several minutes after loss of posture with no righting attempt. This leaves a window of uncertainty in regards to the potential for consciousness after loss of posture during gradual fill gas euthanasia in piglets.
... However, increased line speeds and automation can have negative impacts in terms of welfare. Examples include pre-stun shocks when the wings of poultry enter the waterbath before their heads (45), aversion to high concentrations of CO 2 prior to unconsciousness in pigs (46), and incomplete concussion following captive bolt stunning, due to incorrect marksmanship, gun/cartridge selection or inadequate equipment maintenance (47,48,49,50). ...
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This paper examines four examples of animal welfare issues, demonstrating the interactions between welfare and economic principles. Welfare issues associated with purebred companion animals are examined in terms of predicted inherited diseases, highlighting the power of supply and demand in perpetuating traits in pets that compromise their well-being. The livestock industry is presented from the point of view of pig production and the impact that a major disease (pleurisy) has on production and the animals’ welfare. The authors investigate the con icting and complementary demands of animal welfare and economic gains during the transport and slaughter of livestock and poultry. Finally, wildlife species are considered in terms of their prevalence as pests, and the different types of economic analysis that have been conducted to understand the losses caused by these organisms. Also included in this example are decisions made about cost effectiveness and opportunity costs, and regulatory and nancial barriers to the development of humane control agents. In conclusion, animal welfare is illustrated as a central factor in the bene ts that humans enjoy from the role played by animals in society. There are, however, trade- offs between optimal animal welfare and meeting the needs of modern human society.
... Initial CO 2 concentration and fill rate of the chamber have been reported as important factors for respiratory distress and time to loss of consciousness (Gerritzen, Lambooij, Hillebrand, Lankhaar, & Pieterse, 2000;Velarde et al., 2007). In this study, increased respiratory effort and heaving were observed before head recumbency in both groups, suggesting that there was a period of respiratory distress before loss of consciousness. ...
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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.
... However, increased line speeds and automation can have negative impacts in terms of welfare. Examples include pre-stun shocks when the wings of poultry enter the waterbath before their heads (45), aversion to high concentrations of CO 2 prior to unconsciousness in pigs (46), and incomplete concussion following captive bolt stunning, due to incorrect marksmanship, gun/cartridge selection or inadequate equipment maintenance (47,48,49,50). ...
... Neindre et al., 2009;Atkinson et al., 2012;Landa, 2012;Llonch et al., 2012aLlonch et al., , 2012bLlonch et al., , 2013 Postures and movements e.g. kicking, tail flicking, avoidance Jongman et al., 2000;EFSA, 2005;McKeegan et al., 2006;Gerritzen et al., 2007;Velarde et al., 2007;Kirkden et al., 2008;Svendsen et al., 2008;Dalmau et al., 2010;Atkinson et al., 2012;Landa, 2012;Llonch et al., 2012aLlonch et al., , 2012bLlonch et al., , 2013 Autonomic responses e.g. heart rate, blood pressure, respiratory rate, body temperature, dilatation of the pupil, sweating Martoft et al., 2001;EFSA 2005;Gerritzen et al., 2007;Rodriguez et al., 2008;Svendsen et al., 2008;Dalmau et al., 2010;Le Neindre et al., 2009;McKeegan et al., 2011;Atkinson et al., 2012;Landa, 2012;Llonch et al., 2012a Brain activity e.g. ...
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The Panel on Animal Health and Welfare was asked to deliver a scientific opinion on the use of carbon dioxide for stunning rabbits. Specifically, EFSA was asked to give its view on the findings of the study performed by the Polytechnic University of Valencia (Spain) and the Animal Technology Centre CITA-ITAVIA “Estudio sobre la valoración mediante parámetros técnicos y de manejo del sistema de aturdimiento con gas CO2”. As a first step, the type of study, critical variables, experimental design, data collection and analysis and reporting methods needed to supply scientific evidence that the use of CO2 is an acceptable alternative for the stunning of rabbits were defined. These criteria were then applied to the study. The submitted study is not adequate for a full welfare assessment of the alternative method studied because it does not fulfil the eligibility criteria and the reporting quality criteria defined in this opinion. The shortcomings of the study have been highlighted to indicate where improvements are required. To be considered for a full assessment of the welfare implications of the use of high concentrations of CO2 as a stunning method for rabbits, a study must meet the eligibility standards described herein. A full assessment of the welfare implications of the use of high concentrations of CO2 as a stunning method for rabbits would need to take into account the restraining methods, the pre-stunning, and the stunning phases of the slaughter process and the correlation of the study findings with the results of other scientific evidence.
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.
Article
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In accordance with the Austrian Animal Welfare Act, pigs with severe pain or suffering must be killed immediately if a therapy is impossible or economically unreasonable. Such situations occur regularly and each farm should be prepared for emergency killing, in terms both of know-how and of the necessary equipment. Veterinarians should assume a greater responsibility for ensuring the welfare of suffering animals and should contribute more actively to discussions on the emergency killing of moribund farm animals. The aim of this review is to provide specific information concerning the criteria and methods for emergency killing of pigs. Emergency killing must result in a humane and painless death in which the rapid loss of consciousness is followed by brain death, loss of breathing and cardiac arrest. Euthanasia performed by intravenous drug application by a veterinarian is seen as the method of choice for killing moribund pigs of all weight classes. However, the option is limited in farm animals due to its high costs and its availability. To prevent a delay in emergency killing, other proven methods must be applied by the stockman. Moribund suckling piglets may be killed by a manual blow to the head with a heavy instrument (blunt trauma) followed by exsanguination. As this method is not consistent and may be unpleasant for some handlers, the authors suggest the use of nonpenetrating captive bolt pistols specially developed for on-farm euthanasia of moribund suckling piglets. A penetrating captive bolt can be used to stun all pigs that have to be killed after the suckling period, followed by killing by physical destruction of the brain (pithing) or exsanguination. The decision when to euthanize a pig is difficult for the veterinarian but especially so for the handler. In contrast to the situation in Australia and North America, there are no published recommendations for emergency killing in Europe. The present paper provides scientific information on indications and decision- making for the euthanasia of pigs at the farm level. The authors hope that it will encourage animal health service bodies and associations of pig farmers to provide fact sheets and SOPs with recommendations for the euthanasia of pigs.
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The Panel on Animal Health and Welfare was asked to deliver a scientific opinion on two studies performed by IRTA: “Evaluation of the electrical stunning effectiveness in sheep with a current intensity lower than 1 Ampere” and “Evaluation of the electrical stunning effectiveness with electric currents lower than 1 A in lambs and kid goats”. To achieve this, the first step was to define the type of study, critical variables, experimental design, data collection and analysis and reporting needed to supply scientific evidence that a given electrical stunning protocol of small ruminants provides a level of animal welfare at least equivalent to that ensured by the use of a minimum current of 1 A. These criteria were then applied to the two IRTA studies. The submitted studies are not adequate for a full welfare assessment of the alternative method studied because they do not fulfil the eligibility criteria and the reporting quality criteria defined in this opinion. The shortcomings of the studies are identified to make clear where improvements are required. To be considered for a full assessment of the welfare implications of the use of minimum currents lower than 1 A for electrical stunning of small ruminants a study must meet the eligibility standards described herein. A full assessment of the welfare implications of the use of minimum currents lower than 1 A for electrical stunning of small ruminants would need to take into account the restraining methods, the pre-stunning, and the stunning phases of the slaughter process and the correlation of the study findings with the results of other scientific evidence.
Article
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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.
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.
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Humane slaughter implies that an animal experiences minimal pain and distress before it is killed. Stunning is commonly used to induce insensibility but can lead to variable results or be considered unsatisfactory by some religious groups. Microwave energy can induce insensibility in rats, and high power equipment has recently been developed for sheep and cattle. We examined the effectiveness of different settings for microwave energy delivery, power and duration, to induce insensibility based on electroencephalography (EEG) of anaesthetised cows, using the minimal anaesthesia model. All applications resulted in the appearance of seizure-like complexes in the EEG, a pattern considered incompatible with awareness. Shorter duration of application resulted in more rapid EEG changes, as quickly as 3 s. Higher power resulted in a longer duration of EEG suppression, at least 37 s and up to 162 s. Microwave energy can induce insensibility in cattle based on seizure-like complexes in the EEG.
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The objective of this study was to evaluate the effects of chamber stocking rate on facets of animal welfare and efficacy during gas euthanasia of young pigs (Sus scrofa domesticus). Crossbred pigs (390 neonatal and 270 weaned) designated for euthanasia at production farms were randomly assigned to group sizes of one, two, four, or six pigs. Gas euthanasia of each piglet group was performed in a Euthanex® AgPro chamber. The chamber air was gradually displaced with CO2 gas over 5 min to establish an in-chamber concentration of approximately 80% CO2. Pigs remained in that atmosphere for an additional dwell period of at least 5 min. Higher stocking rates were associated with higher CO2 concentrations after gradual fill for both age groups. While there was no evidence of an effect of stocking rate on latencies to loss of posture or last movement in neonatal pigs, there was evidence of an effect on all measured efficacy variables in weaned pigs, with grouped pigs faster to succumb than solitary pigs. This finding is consistent with expected consequences of higher CO2 concentration at increased stocking densities. Aversive states and behaviours of focal pigs in the chamber were scored from video. Weaned solitary pigs displayed a high incidence of pacing and may have experienced isolation distress. Escape attempts were absent in neonates and not linearly affected by stocking rate in weaned pigs. Although the risk of hazardous interactions was correlated with group size, this study provided no evidence that isolation during gas euthanasia would benefit animal welfare.
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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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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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The objective of this study was to assess the aversion to exposure of 90% argon, 70% N2/30% CO2 and 85% N2/15% CO2 by volume in atmospheric air in 24 halothane-free slaughter-weight pigs using aversion learning techniques and behavioural studies in an experimental slaughterhouse. Pigs were subjected to the treatments individually during 2 separate trials of 12 animals each. The time of exposure to the gases was 46 and 32 s, respectively. When the pit contained any of the 3 gas mixtures, the time taken to cross the raceway and enter the cradle (TCREC) increased compared with the training sessions (atmospheric air). The incidence of pigs showing retreat and escape attempts and gasps and the number of times that this behaviour was performed was lower in 90% argon than in the gas mixtures with N2 and CO2. On the other hand, the time to loss of posture was lower with 70% N2/30% CO2 than with argon. The second exposure to all gas mixtures was more aversive than the first and the loss of posture also occurred earlier in the second exposure. In conclusion, pigs showed more aversion to gas mixtures with N2 and either 15% or 30% CO2 by volume than 90% argon by volume.
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This guidance defines the process for handling applications on new or modified stunning methods and the parameters that will be assessed by the EFSA Animal Health and Welfare (AHAW) Panel. The applications, received through the European Commission, should contain administrative information, a checklist of data to be submitted and a technical dossier. The dossier should include two or more studies (in laboratory and slaughterhouse conditions) reporting all parameters and methodological aspects that are indicated in the guidance. The applications will first be scrutinised by the EFSA's Applications Desk (APDESK) Unit for verification of the completeness of the data submitted for the risk assessment of the stunning method. If the application is considered not valid, additional information may be requested from the applicant. If considered valid, it will be subjected to assessment phase 1 where the data related to parameters for the scientific evaluation of the stunning method will be examined by the AHAW Panel. Such parameters focus on the stunning method and the outcomes of interest, i.e. immediate onset of unconsciousness or the absence of avoidable pain, distress and suffering until the loss of consciousness and duration of the unconsciousness (until death). The applicant should also propose methodologies and results to assess the equivalence with existing stunning methods in terms of welfare outcomes. Applications passing assessment phase 1 will be subjected to the following phase 2 which will be carried out by the AHAW Panel and focuses on the animal welfare risk assessment. In this phase, the Panel will assess the outcomes, conclusions and discussion proposed by the applicant. The results of the assessment will be published in a scientific opinion.
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.
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.
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A test widely used to assess fear and novelty responses in domestic species is the open field. The aim of this study was to investigate the effect of RYR(1) genotype on open field behavior in growing pigs. The study subjected 15 heterozygous (Nn) and 15 RYR(1)-free (NN) gilts of 19 weeks of age to 3 replicates of an open field test 2 days apart from each other. The study measured the number of grid lines crossed and defecation score in the test arena. There was a significant individual correlation among the 3 replicates of the test, both for number of grid lines crossed and defecation score (p <.05). RYR(1) genotype had a significant effect on number of grid lines crossed, with NN gilts showing more overall activity than Nn gilts (p <.05). The study observed no significant differences in defecation score between genotypes. This result suggests that the RYR(1) genotype may have an effect on the appraisal of novelty. Thus, it would be interesting to take this factor into account when using this methodology to assess fear responses in pigs and in interpreting the results with respect to welfare.
Article
The effect of the halothane gene on certain growth and meat quality characteristics were investigated by comparing the three known halothane genotypes (NN, Nn, nn). Fifty nine Landrace × Large White pigs (gilts = 25, castrates = 34; NN = 31, Nn = 17, nn = 11) were reared from 27 to 86 kg liveweight, whereafter the pigs were slaughtered and meat and carcass quality characteristics measured. Average daily gain (ADG), days to slaughter and carcass length showed significant genotype × sex interaction. The nn pigs showed the highest ADG and least days to slaughter, followed by the NN and then the Nn pigs. The castrates grew significantly faster with a higher ADG (p < 0.05) and fewer days to slaughter (p < 0.001). Carcass length did not differ for different genotypes or sexes. NN pigs had the highest meat depth, predicted lean meat percentage (LMP) and lowest fat thickness, followed by the Nn and nn pigs. The castrates had a higher fat thickness (p < 0.05) with a resultant lower LMP (p < 0.05) compared to gilts. None of the genotypes or sexes showed differences in chilling loss, but drip loss differed between genotypes (p < 0.05) and sexes (p < 0.001), with nn pigs having the lowest drip loss. The pH 1 values differed (p < 0.05) between genotypes, with NN the highest and nn the lowest. No differences in pH 24 were observed between genotypes. The pH 1 and pH 24 values did not differ between sexes. Although the presence of the halothane gene positively affected growth rate, this increase in growth rate was largely due to undesirable fat deposition. Furthermore, the gene did not positively affect meat quality (pH 1) or carcass quality (LMP). Therefore, the intentional use of the halothane gene is discouraged.
Article
Thirty-six Merino wethers were forced along a sheep race and were either electro-immobilized using a commercially-available instrument, restrained with the electro-immobilizer electrodes attached, physically restrained in a sheep-handling machine or allowed to run freely through the race. The degree of aversion shown to the place where the treatment occurred was measured by the time taken by the sheep to run through the race on a subsequent occasion (“transit time”) and the push-up time required. All forms of restraint increased the push-up and transit times. Sheep that had been electro-immobilized had a greater average transit time after four treatments and a greater average push-up time after two treatments than sheep that were physically restrained, with or without the electrodes attached. These results suggest that sheep find electro-immobilization more aversive than physical restraint. Push-up time was increased if a high current was used, but was unrelated to the duration of electro-immobilization (up to 3 min). Increasing the current increased the time required by the sheep to recover breathing, which was strongly and positively related to subsequent push-up time. The degree of aversion shown decreases with experience of electro-immobilization.
Article
A stunning method that will reliably render an animal insensible to pain and sensation prior to hoisting and bleeding is essential to prevent suffering. Cardiac arrest stunning is more effective than conventional electric stunning. In cardiac arrest stunning, an electric current is passed through both the brain and the heart to produce permanent insensibility. Since the animal is killed by the electricity it cannot revive during hoisting, bleeding, or slaughtering procedures. In contrast, conventional electrical stunning induces reversible insensibility for a short period of time (Hoenderken 1978a; Grandin 1980a; Warrington 1974; Lambooy and Spanjaard 1982; Blackmore and Newhook 1981).
Article
Two methods widely accepted for measuring muscle/meat pH are: (1) homogenizing muscle tissue in 5 mM iodoacetate and (2) spear-tip penetrating probe electrode. These two methods were compared with a third method to evaluate the precision of these methods for measuring muscle pH. The third method involved homogenizing tissue in deionized water and measuring pH within 3–5 set of homogenization. It was verified that pH values measured within 3–5 set of homogenization using deionized water were statistically equivalent (P>0.O5) to those measured using the iodoacetate procedure or a spear-tip probe electrode.
Article
Measurements of light scattering and electrical conductivity were made in the Longissimus dorsi (LD) and Semimembranosus (SM) muscles using the Fibre Optic Probe (FOP) and Quality Meter (QM), respectively, to assess their ability to estimate pig meat quality, particularly the occurrence of PSE meat. One-hundred-and-fifty-three gilt carcasses were measured on three occasions post mortem (pm): 45 min (FOP(45) and QM(45)), 2h (FOP(2) and QM(2) and 24 h (FOP(u) and QM(u)). Measurements of pH were taken in the same anatomical position and at the same times. At 24 h pm muscle reflectance (GOFO value) and subjective colour assessments were made on the cut surface of the LD at the level of the last rib. Water-holding capacity (WHC) was estimated in a sample taken from the exposed surface of the LD by the solubility of sarcoplasmic and myofibrillar proteins. The FOP(45) predicted most accurately the WHC (R(2) = 0·49). Neither of the other quality measurements improved the prediction at 45 min pm. However, at 2h, adding QM(2) as a second independent variable improved prediction of WHC (R(2) = 0.58). At 24 h the combination of FOPu, QMu and GOFO did not improve the prediction of WHC (R(2) = 0.58). The best prediction used measurements of FOP(45), QM(2) and GOFO (R(2) = 0·62). The best relationship between subjective colour scores and the quantitative measurements of meat quality using discriminant analysis was obtained with the FOPu with an error-count estimate of 15·1% followed by FOP(2) (17%), GOFO value (18·7%), pH(2) (19·7%) and QMu (20·2%). With combination measurements of two instruments, pH(2) and FOP(2) had the lowest error-count estimate (10·9%). No further precision was obtained with combinations of three instruments. These results suggest that FOP and QM can be used to predict PSE and normal pig meat at different times pm and can replace traditional pH muscle measurements.
Article
The relation between the intrinsic carcass and meat quality and the organoleptical characteristics of three genotypes of pigs was studied. In total 411 pigs, consisting of 121 BL-genotype pigs, 115 hybrids (Seghers Hybrid) and 175 Large White-genotype pigs, were screened. Slaughter day and genetic background had a great impact on the intrinsic meat quality parameters. The factor 'slaughter day' implies the stunning method besides the total specific transport and slaughter conditions. Whatever the genetic background is, halothane susceptibility is obviously the crucial factor. Selection against the halothane gene positively influences the intrinsic and sensory meat quality parameters. This study also suggests that an increase in the intramuscular fat content, if desirable in the interest of the sensory meat quality, can be achieved without deterioration of the zoo-technical performance and the carcass quality of the pigs.
Article
Two commercial pig abattoirs (A and B) equipped with a head-only and head-to-chest electrical stunning systems, and two (C and D) equipped with compact carbon dioxide (CO(2)) stunning systems, were visited during 3 days to evaluate the effects of the stunning system on meat quality and haemorrhages. Meat quality was evaluated by measuring muscle electrical conductivity (PQM) and colour (Minolta Chromameter) at 2 and 7 h post mortem (abattoirs A and C, and B and D, respectively). PQM and colour were measured in 2486 and 2321 loins respectively. Also ultimate pH (pHu) was measured in 2395 loins at 24 h post mortem. Haemorrhages were evaluated by recording the incidence of petechiae, ecchymosis and haematomas, bone fractures were also recorded. A total of 1980 shoulders, 3943 loins, and 5438 hams were inspected. In the abattoirs equipped with the electrical stunning systems, a higher (P<0.05) incidence of potentially PSE meat (PQM>6) was found compared with the abattoirs equipped with CO(2) stunning. Likewise, the loins from electrically stunned pigs were paler than those from CO(2) stunned pigs (P<0.05). Electrical stunning increased the incidence of petechiae in the loin and the ham (P<0.05). No shoulder, loin or ham with bone fractures was found in the abattoirs studied. Therefore, CO(2) stunning reduces the incidence of PSE meat and of petechiae on muscle fascia of loins and hams, compared with electrical stunning. However, petechiae are not of great importance because they can be removed from the affected commercial cuts.
Article
The effects of halothane genotype on muscle metabolism at slaughter and its relationship with meat quality were studied within 16 litters. Heterozygous boars and sows were mated and the offspring were halothane tested and bloodtyped to reveal the halothane (Hal) genotype of the 120 animals used (NN, Nn or nn). Following slaughter at 100kg live weight, muscle samples from M. longissimus dorsi (LD) and M. quadriceps (Qu) were taken immediately after exsanguination and analysed for glycogen, glucose-6-phosphate, lactate, creatine phosphate (CP), and adenosine triphosphate (ATP), as well as for enzyme activities representing both the oxidative and glycolytic pathways. The enzyme activities were similar for all genotypes. All muscle metabolites differed significantly between samples from NN and nn animals, with higher lactate and glucose-6-phosphate and lower glycogen, CP and ATP in the nn muscles. The heterozygote animals were intermediate or close to either of the homozygotes. Meat quality characteristics (drip loss, surface and internal reflectance and dielectric loss factor) were studied only in the LD muscle. Meat quality of the muscle from the heterozygote (Nn) animals was inferior to that from NN animals (no difference for internal reflectance) but better than that from nn animals. When reflectance and drip loss were combined into an index, very few values from the nn-animals were better than the total mean. Indexes from the dominant homozygotes were generally better than the mean and those of heterozygotes were approximately normally distributed around the mean.
Article
Groups of pigs were anaesthetized on a number of occasions with concentrations of CO2 ranging from 50%–80%. In all cases the exposure time was 45 seconds. Behavioural effects before loss of consciousness and recovery time after exposure to the varying concentrations of CO2 were noted. In some pigs electrocardiograph recordings were made during recovery and in others arterial or venous blood samples were taken for blood gas analysis. The results indicate that at the concentrations of CO2 which are used commercially for stunning, that is 66%–70%, approximately half of the pigs were standing within one minute of their return to atmospheric air. Some degree of excitement was seen at all CO2 concentrations but it was difficult to assess whether this was more marked at higher concentrations. Certain individual pigs, however, reacted violently whatever the concentration. With concentrations of CO2 ranging from 76%–80% all the pigs in this trial remained in lateral recumbency for at least a minute after their removal from the CO2 chamber and in some cases they remained recumbent for over two minutes. In all cases where the electrocardiogram was recorded the pigs had paroxysmal ventricular tachycardia immediately before standing. The blood gas results show that all the pigs had some degree of hypoxaemia and that they all had metabolic and respiratory acidosis.
Article
Sheep were repeatedly chased down a race and were then either subjected to the noise of a shearing handpiece or had wool shaved off. An increase in the time that had to be spent pushing the sheep down the race indicated that the latter treatment was aversive. Similar results were obtained when the sheep were subjected to the same two treatments while electro-immobilised. This throws doubt on the analgesic effectiveness of electro-immobilisation.
Article
The open field test (OFT) was carried out on Wistar and Sprague-Dawley rats between the ages of 3 to 20 weeks. At that time, the behavior of each naive rat was observed for two 3-minute periods separated by an interval of 24 h (Day). The OFT scores varied depending on the day and the age. Comparatively higher activity was observed in the extent of ambulation and rearing at 5 weeks old, rearing and preening at 7 weeks old, and preening and defecation at 11 weeks old in the Sprague-Dawley rats compared with the Wistar rats.
Article
In the laboratory rat, inhalation (30 s) of high (> 70%) CO2 concentrations resulted in short-term (1-3 min) anesthesia, followed by a prolonged (up to 60 min) mild antinociception. Exposure to 100% CO2 resulted in significant thermal (hot-plate, 52 degrees, and tail-flick) and mechanical (tail-pinch, 886 g force) antinociception. Control animals, placed in the same chamber filled with air, showed no such effects. Rats exposed to 70% CO2 exhibited effects on the hot plate comparable to those seen after inhalation of 100% CO2, indicating that the response is not due to CO2-induced hypoxia. Additionally, recovery from halothane-induced anesthesia of comparable duration did not result in antinociception, confirming that anesthesia alone is not sufficient to produce the effect. Pretreatment with the opiate antagonist naltrexone (0.1-10 mg/kg i.p.) did not diminish the CO2-induced antinociception, suggesting that endogenous opioids are not obligatory in the mechanism of this response. Furthermore, hypophysectomy abolished hot-plate antinociception in animals exposed to 100% CO2 while sham-treated controls exhibited a pattern of hot-plate responses similar to that reported above. Taken together, these findings show that: (1) recovery from CO2-induced anesthesia results in a prolonged mild antinociception, detectable with thermal and mechanical nociceptive tests; and (2) this response may represent a novel from of environmentally induced antinociception, mediated by a non-opiate hormonal substance.
Article
1. Most quantitative examinations of nociception are performed with thermal or mechanical stimuli. Because nociceptive processing mechanisms may depend on the modality of the stimuli, comparable studies on chemonociception are necessary. 2. We examined the activity of chemonociceptive medullary dorsal horn neurons in halothane-anesthetized rats. For controlled noxious chemical stimulation, defined CO2 pulses were applied to the nasal mucosa. The effects of stimulus intensity, duration, and interstimulus interval (ISI) were tested by performing three different CO2 stimulation protocols (see below). 3. The recorded neurons were characterized by intranasal and facial stimuli of different modalities. The cells received input from intranasal A delta- and/or C-fibers. All tested neurons also responded to other intranasally applied irritants, e.g., mustard oil. Furthermore, the units were sensitive to intranasal high-threshold mechanical stimulation and to facial mechanical stimulation. According to the properties of their facial mechanoreceptive fields, the units were classified as wide dynamic range (WDR) or nociceptive specific (NS) neurons. The majority of the cells also responded to facially applied noxious heat stimuli, so that most of the recorded neurons were found to be multimodal. Some of the neurons, in addition, had convergent input from primary afferents innervating the maxillary tooth pulps or the cornea and periorbital structures. 4. In the first stimulation protocol we presented four different CO2 concentrations (25, 50, 75, and 100%; stimulus duration 2 s). In total, each concentration was applied 10 times (2 trains of 5 stimuli). Stimulus response functions (SRFs) were computed with average responses to identical stimuli. All but 2 of the 23 tested neurons displayed enhanced responses after stimulation with increasing intensities. In general, WDR cells (n = 15) discharged more vigorously to the same CO2 concentration than NS cells (n = 8). WDR neurons discriminated more reliably between stimulus intensities in the low to moderate range (25-50% CO2) than NS cells. Both categories of neurons, however, discriminated equally well in the moderate- to high-intensity range (50-75% CO2). The discriminatory capacity of WDR and NS neurons was reduced in the highest concentration range (75-100% CO2). The proportion of NS neurons significantly discriminating between these intensities tended to be higher compared with WDR neurons when stimuli were applied with long ISIs (120 s). 5. To examine the effects of the duration of the ISI, identical test sequences were performed with ISIs of 30 and 120 s. (ABSTRACT TRUNCATED AT 400 WORDS)
Article
This lab previously showed that brief inhalation of high concentrations of CO2 results in a prolonged, moderate antinociception with characteristics of a nonopiate, hormonal mechanism. To further characterize and optimize this response, the effect of a variety of methodological, biological, and stress-related manipulations were studied. No significant differences were found in the CO2-induced response between animals that were tested during different portions of their diurnal cycles, in rats that were unhandled or habituated to nociceptive testing conditions, in male vs. female rats, or in animals of differing weights. Additionally, restraining animals prior to CO2 exposure induced a hot plate antinociceptive response that was not different from the response produced by CO2 alone. In contrast, on the tail flick test, a CO2 -restraint interaction both increased and decreased the response at different times. The present findings show that CO2 antinociception: a) is a reliable phenomenon not altered by a variety of methodological and biological conditions, and b) has characteristics of a novel, stress-mediated antinociceptive response.
Article
Using aversion learning techniques, the relative aversiveness of CO(2) to pigs in comparison to a shock with an electric prodder, and the aversiveness of a CO(2)-stunner crate in comparison to the aversiveness of a V-belt restrainer used for electric stunning were examined. The results showed that 90% CO(2) was considerably less aversive than an electric shock with a prodder. However, during exposure to 90% CO(2) all pigs lost conscious, which may have affected their memory of the procedure. The pigs remained conscious after exposure to 60% CO(2) and again showed virtually no aversion towards the stunner crate, while an electric shock with a prodder appeared highly aversive. The aversion to the V-restrainer belt and the CO(2) crate were similar.
Physiology of stress, distress, stunning and slaughter
  • N G Gregory
Gregory, N. G. (1998). Physiology of stress, distress, stunning and slaughter. In N. G. Gregory, & T. Grandin, Animal welfare and meat science (pp. 64±92). Willingford, UK: CAB International.
Performance and carcass characteristics of pigs with known genotypes for halothane susceptibility
  • P Jensen
  • P A Barton-Gade
Jensen, P., & Barton-Gade, P. A. (1985). Performance and carcass characteristics of pigs with known genotypes for halothane susceptibility. In J. B. Ludvigsen, Stress susceptibility and meat quality in pigs (pp. 80±87). European Association of Animal Production Publication no 33.
Stunning of animals for slaughter (pp. 73±81). The Hague
  • G In
  • Eikelenboom
In G. Eikelenboom, Stunning of animals for slaughter (pp. 73±81). The Hague, The Netherlands: Martinus Nijho€.
Stunning of animals for slaughter
  • In G Eikelenboom
In G. Eikelenboom, Stunning of animals for slaughter (pp. 73±81). The Hague, The Netherlands: Martinus Nijho.