Assessment of unconsciousness during carbon dioxide stunning in pigs

Rodríguez, P.; Dalmau, Antoni; Ruiz-de-la-Torre, J.L.; Manteca, Xavier; Jensen, EW; Rodriguez, Bernardo E.; Litvan, H.; Velarde, Antonio

doi:10.1017/s0962728600027834

Cited by 48 publications

(10 citation statements)

References 22 publications

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“…An atmosphere with high concentrations of carbon dioxide (CO 2 ) (> 80% by volume in air) induces hypercapnic hypoxia in the dam and inhibits neurones through acidosis. During CO 2 inhalation, partial pressure of oxygen (pO 2 ) and oxygen saturation (SatO 2 ) in the blood decrease progressively (Rodriguez et al, 2008), and induces respiratory and metabolic acidosis, reduces the pH of cerebrospinal fluid (CSF), which bathes the brain and spinal cord and neurons, thereby exerting its neuronal inhibitory and anaesthetic effects (Woodbury and Karler, 1960). Consequently, the animal loses consciousness (Gregory, 1986).…”

Section: Gas Stunningmentioning

confidence: 99%

Animal welfare aspects in respect of the slaughter or killing of pregnant livestock animals (cattle, pigs, sheep, goats, horses)

More¹,

Bicout²,

Bøtner

et al. 2017

EFS2

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This scientific opinion addresses animal welfare aspects of slaughtering of livestock pregnant animals. Term of Reference (ToR) 1 requested assessment of the prevalence of animals slaughtered in a critical developmental stage of gestation when the livestock fetuses might experience negative affect. Limited data on European prevalence and related uncertainties necessitated a structured expert knowledge elicitation (EKE) exercise. Estimated median percentages of animals slaughtered in the last third of gestation are 3%, 1.5%, 0.5%, 0.8% and 0.2% (dairy cows, beef cattle, pigs, sheep and goats, respectively). Pregnant animals may be sent for slaughter for health, welfare, management and economic reasons (ToR2); there are also reasons for farmers not knowing that animals sent for slaughter are pregnant. Measures to reduce the incidence are listed. ToR3 asked whether livestock fetuses can experience pain and other negative affect. The available literature was reviewed and, at a second multidisciplinary EKE meeting, judgements and uncertainty were elicited. It is concluded that livestock fetuses in the last third of gestation have the anatomical and neurophysiological structures required to experience negative affect (with 90-100% likelihood). However, there are two different possibilities whether they perceive negative affect. It is more probable that the neurophysiological situation does not allow for conscious perception (with 66-99% likelihood) because of brain inhibitory mechanisms. There is also a less probable situation that livestock fetuses can experience negative affect (with 1-33% likelihood) arising from differences in the interpretation of the fetal electroencephalogram, observed responses to external stimuli and the possibility of fetal learning. Regarding methods to stun and kill livestock fetuses at slaughter (ToR4), sets of scenarios and respective actions take account of both the probable and less probable situation regarding fetal ability for conscious perception. Finally, information was collated on methods to establish the dam's gestational stage based on physical features of livestock fetuses (ToR5).

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Section: Gas Stunningmentioning

confidence: 99%

Animal welfare aspects in respect of the slaughter or killing of pregnant livestock animals (cattle, pigs, sheep, goats, horses)

More¹,

Bicout²,

Bøtner

et al. 2017

EFS2

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show abstract

“…For example, in the comparison described above, the new method may result in a faster loss of posture, but the animals show a higher level of escape attempts. In that case, a qualitative step is needed to evaluate the different measures in combination with each other: a 'weighting' of both measures is required to be able to compare their relative importance for animal welfare (Spoolder et al, 2003).…”

Section: Qualitative Approachesmentioning

confidence: 99%

“…For example, poor welfare outcomes such as 'gasping' during gas stunning can be compared qualitatively with 'wing flapping' during shackling associated with electrical stunning. Spoolder et al (2003) discussed different techniques for qualitative comparisons. Most commonly, the measure scores are linked to a range or step indicating 'severity', which can then be compared quantitatively.…”

Section: Qualitative Approachesmentioning

confidence: 99%

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Guidance on the assessment criteria for applications for new or modified stunning methods regarding animal protection at the time of killing

Bicout

Bøtner³

et al. 2018

EFS2

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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.

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“…Additionally, the circulatory system must supply sufficient oxygen. Such dependency justifies the use of arterial blood sampling in previous studies [2,9,18,19]. However, it is technically challenging not only to sample arterial blood from pigs in the stunning environment but to be able to reliably link samples with rapidly changing behavioural events.…”

Section: Introductionmentioning

confidence: 99%

CO2 Stunning in Pigs: Physiological Deviations at Onset of Excitatory Behaviour

Hognestad,

Digranes,

Opsund

et al. 2023

Animals

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Stunning by carbon dioxide (CO2) inhalation is controversial because it is associated with vigorous movements and behaviours which may or may not be conscious reactions. Furthermore, it is unknown whether some behaviours might indicate the transition into unconsciousness. Our study objective was to investigate the loss of consciousness during CO2 stunning by linking physiological variables (in particular pH, PaO2 and PaCO2) to the onset of observed behaviours. A total of 11 cross-bred pigs were studied. A tracheostomy tube, venous and arterial cannulae were placed under sevoflurane anaesthesia. After recovery from this, and a “wash out” period of at least 30 min, arterial blood samples were taken (and baseline values established) before 90–95% CO2 in medical air was administered through the tracheostomy tube. Subsequent behaviours were video-recorded and key physiological variables were evaluated using an anaesthetic monitor and the frequent sampling of arterial blood (albeit with inconsistent inter-sample intervals). After the study, behaviours were classified in an ethogram. At the onset of behaviours categorised as “vigorous movement extremities”, “opisthotonos” and “agonal gasping” pH values (range) were: 6.74–7.34; 6.66–6.96 and 6.65–6.87, while PaCO2 (kPa) was 4.6–42.2, 24.4–51.4 and 29.1–47.6. Based upon these values, we conclude that the pigs were probably unconscious at the onset of “opisthotonos” and “agonal gasping”, but some were probably conscious at the onset of “vigorous movements”.

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Assessment of unconsciousness during carbon dioxide stunning in pigs

Cited by 48 publications

References 22 publications

Animal welfare aspects in respect of the slaughter or killing of pregnant livestock animals (cattle, pigs, sheep, goats, horses)

Animal welfare aspects in respect of the slaughter or killing of pregnant livestock animals (cattle, pigs, sheep, goats, horses)

Guidance on the assessment criteria for applications for new or modified stunning methods regarding animal protection at the time of killing

CO2 Stunning in Pigs: Physiological Deviations at Onset of Excitatory Behaviour

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