Dossier

Pig stunning and bleeding

Slaughter must legally spare animals any avoidable pain, distress or suffering. This implies that moving animals into the stunner and holding them there for the purpose of stunning must be done without causing undue fear and distress as may be shown by animals vocalising and trying to turn back or being reluctant to move. Stunning should apply proper electric current or CO2 concentrations such that animals rapidly lose consciousness and do not recover before they have been killed by bleeding.

Source photo: © A. Velarde, IRTA

This dossier aims to help Competent Authorities and other stakeholders with issues related to welfare of pigs at the time of stunning and killing. The dossier is updated periodically by the EURCAW-Pigs team. The text is meant to support Competent Authorities, and is not legally binding.

The dossier is based on EURCAW-Pigs’ “Review on pig welfare in slaughterhouses around the time of stunning and bleeding”. Three key areas relevant for pig welfare immediately related to stunning and killing are highlighted: (1) Handling, i.e. moving into the stunner and restraint for the purpose of stunning, (2) Stunning, i.e. electrical stunning and CO₂ stunning, for the purpose of rendering animals unconscious, and (3) bleeding, for the purpose of killing.

Each EURCAW-Pigs dossier addresses the following 5 items: ‘Legislation', ‘Welfare indicators’, ‘Knowledge’, 'Inspiring examples' and 'Training courses'. The dossier is updated periodically by the EURCAW-Pigs team.

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Council Regulation (EC) No 1099/2009 regulates legal requirements for pigs at the time of killing. The regulation has been in force in the European Union since 2013, and determines the animal welfare conditions under which livestock should be handled and slaughtered.

Enforcement of Council Regulation (EC) No 1099/2009:

The Member States provide mandatory guidelines for their competent authorities to ensure consistent enforcement of the Council Regulation and the national regulations. These guidelines are notified to the Commission. The Regulation addresses the business operator (BO) for assuring animal welfare in their slaughterhouses. The business operators shall apply guides of good practice developed by his/her own organisations to facilitate the implementation of the Council Regulation.

EURCAW-Pigs’ “Review on pig welfare in slaughterhouses at stunning and bleeding” describes the requirements in more detail.

During handling and moving towards the stunning area, pigs shall be handled according to their biology and to avoid pain and distress. This is because the latter results in pigs hesitating and halting, causing piling up, turning back, slipping or falling, and a suboptimal slaughter process. For each stage of the slaughter process, i.e. unloading from the vehicle, lairage, moving to the stunning area, stunning, possible hoisting, and debleeding, a specified SOP must be in place and applied. This is to be monitored by the Animal Welfare Officer.

Guidance

In EURCAW-Pigs’ “Review of pig welfare in slaughterhouses at stunning and bleeding”, suggestions for improved practices are provided to minimise welfare problems for each of three key areas relevant for pig welfare immediately related to stunning and killing:

Handling prior to stunning

During handling and moving towards the stunning area, pigs shall be handled according to their biology and to avoid pain and distress:

A factor that is extremely stressful is isolation for individual (manual) electrical stunning, or into a single file for automated electric stunning, especially with a high slaughter speed. For CO₂ stunning, pigs are driven in small groups into the stunner, which is less stressful.
The use of excessive pressure can be reduced using simple improvement measures, e.g., management of light and airflow encourages pigs to move into single files before stunning. Disturbing noises should be avoided, e.g. metal gates banging on metal (using rubber protection), noises from hydraulic slaughter apparatus and vocalisations of conspecifics, etc.

Stunning, i.e. electrical and CO₂ stunning

Electrical stunning involves passing an electric current through the brain of the pig to induce a generalised epilepsy and immediate loss of consciousness. Effective electrical stunning results, e.g., in:

Immediate loss of consciousness, collapse of the hind and tonic rigidity followed by tonic-clonic seizures.
Immediate loss of breathing and presence of breathing indicates an ineffective stun.
Recovery may start after 30 sec and de-bleeding takes 20-60 sec to result in cerebral hypoxia, so sticking should be done as fast as possible following stunning, i.e. during or towards the end of the tonic phase or at the very start of clonic activity, and preferably before hoisting of the body.

In Controlled Atmosphere Stunning (CAS) using CO₂small groups of pigs are exposed to a high concentration of CO₂ leading to depression of brain activity and loss of consciousness:

CO₂ (above 40%) is pungent and painful to inhale and leads to highly aversive responses indicative of fear, pain and respiratory distress (‘air hunger’). It takes approximately 15-20 sec before pigs lose consciousness (depending on the CO2 concentration).
Stunning effectiveness depends on e.g. the CO₂ concentration, duration of exposure, maximum stun-to-stick interval and the quality and temperature of the gas.
Devices must be in place displaying and recording the gas concentration and exposure time, and giving an alarm in case of insufficient gas concentration (< 80% CO₂).

Bleeding

Bleeding must be performed soon after stunning to avoid animals regaining consciousness before they die as a result of blood loss:

Slaughter pigs are usually killed by bleeding using a chest stick severing the common brachiocephalic trunk.
Before sticking, unconsciousness of the animals must be ascertained. Animals being conscious at sticking or regaining consciousness during bleeding are likely to have poor welfare, as the incision is painful.

In the next section on welfare indicators, examples of relevant clinical conditions and signs of physiological weaknesses will be listed (forthcoming).

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In addition to the resource and management-based parameters required by law (Regulation 1099/2009) like electrical settings in case of electrical stunning, (records of) gas concentrations in case of CO2 stunning and the stun-to-stick interval, inspectors should use animal-based indicators to assess proper and effective handling, stunning and bleeding. EURCAW-Pigs developed three factsheets, each combining several indicators, one related to handling and moving pigs to the stunner, and two related to monitoring of stunning and bleeding efficiency (see ‘Show more’).

Distress and fear behaviours: High levels of fear and distress when handled and moved to the stunning area can be assessed or scored by frequency of high pitch vocalisations, turning back or refusing to move, and slipping and falling.

Animal-based indicators are used to measure the effectiveness of stunning and bleeding. They should be tested with caution:

To test electrical stunning efficiency, pigs are preferably assessed immediately after ejection, after ca. 40 sec., and during bleeding / before further slaughtering. First observations after the ejection from the stunning box include a visual check of the presence of a tonic state, absence of directed movements, vocalisations, regular breathing or a spontaneous blinking. About 40 seconds after the end of the current flow through the head additional reflex tests such as the palpebral or corneal reflex tests and the pain reflex test can be performed.
Efficiency of CO2 stunning is monitored immediately after ejection, after sticking, and during bleeding / before further slaughtering. Signs of return of consciousness are recovery of breathing (incl. gasping), positive corneal reflexes, or spontaneous blinking of the eye lids. Signs of consciousness are a righting reflex, regular breathing, reproducible reactions to pain stimuli, corneal or palpebral reflex tests, and vocalisations.

Source photo: ©Brand Qualitätsfleisch

The PigStun project runs from January 2022 – May 2025 with the aim to improve animal welfare during the stunning process of pigs in slaughterhouses. In this European project researchers and slaughterhouses in Germany, Denmark, Spain and the Netherlands worked together to test alternative stunning methods for pigs to replace conventional CO2 stunning.

Read more about the PigStun project

For good practices of implementation of EU legislation, seen in a full systems context, inspiring examples and demonstrators are identified. The examples given here address some good practices regarding calm and attentive handling of the animals from unloading to death. Demonstration of good practices are excellent ways and proven methods of dissemination of knowledge, exchanging ideas, harmonizing assessments, and changing attitudes. Brand Qualitätsfleisch is a medium-sized slaughterhouse in Lohne, Germany, where transparency and animal welfare at slaughter play a particularly important role.

The management including the selection of farmers, short transport times, calm and attentive handling of the animals from unloading to stunning and bleeding are implemented in an exemplary manner at this abattoir. A calm atmosphere in the lairage and during driving the animals to the CO2-stunner, a continuously visible bleeding line and well-trained staff are reflected in calm animal behaviour, which for example means that little driving pressure has to be exerted. In addition, new future looking methods are constantly being tested, such as a new floor covering and lightning in the unloading and lairage area as well as automatic systems for bleeding control or recording vital signs on the bleeding line, which advance animal welfare.

Disclaimer: This is not an endorsement.

The slaughterhouse Thönes-Natur-Verbund in Wachtendonk, Germany, specializes in the slaughter of pigs that meet the quality requirements of the Naturverbund (organic and Thönes-Natur). The company has developed a special u-shaped raceway to the electrical stunner. On the one hand, the short drive aisle reduces the period of stressful singling/separation of the pigs, which is always necessary before electric stunning. On the other hand, the curved design gives the animals the feeling of moving back to the starting direction, i.e. back to the other pigs.

In addition, good illumination of the stunning device supports the animals' entry. Overall, this u-shaped system allows one person to calmly move pigs to the stunner with minimal use of driving tools and low stress, which in turn can have a positive impact on the stunning effectiveness.

Disclaimer: This is not an endorsement.

It may be helpful for Competent Authorities (CAs) and inspectors to get an impression of the possibilities to monitor animal-related measures in slaughterhouses through the application of sensor technology and artificial intelligence (AI). Sensor technology cannot yet replace a human during the meat inspection, but it has potential to play an important role in the future.

Currently it can already add value to the inspections and provide better insight into animal welfare issues than by human inspections alone (Voogt et al., 2023). This document provides several examples of digital technology systems to improve animal welfare.

Disclaimer: This is not an endorsement.

In collaboration with national training bodies and national reference centres on animal welfare, training guides are developed for the different welfare topics as standards for national training in EU Member States.

Learning goals

On the subject of stunning and bleeding:

Knowledge about the intention of the EU-legislation (Protection of animals at the time of killing).
Updated knowledge about handling of pigs when moved and restrained for stunning under different settings.
Updated knowledge about approved methods for stunning and bleeding.
Knowledge on key technical parameters to monitor when assessing the equipment used for the different methods for stunning (technical stunning parameters and operational capability).
Knowledge about animal based indicators to assess the stunning and bleeding process.
Practical training in using the EURCAW indicators and identifying failures in the processes.
Knowledge about necessary measures in case of failures (backup procedures, instructions for troubleshooting and optimization of stunning and bleeding).
Knowledge about challenges in relation to communication with abattoir workers during
inspection.

Inspection-driven welfare improvement

Additionally, EURCAW-Pigs provides examples of training plans and materials used in different Member States in English, to the extent possible, and training suggestions for improvement of communication skills and ways to support inspection-driven welfare improvement. This is presented on the training overview page.