Terrestrial Animal Health Code

Contents | Index Chapter 7.6. Section 7. Chapter 7.6.

Chapter 7.6.


Killing of animals for
disease control purposes


Article 7.6.1.


General principles

These recommendations are based on the premise that a decision to kill the animals has been made, and address the need to ensure the welfare of the animals until they are dead.

  1. All personnel involved in the humane killing of animals should have the relevant skills and competencies. Competence may be gained through formal training and/or practical experience.

  2. As necessary, operational procedures should be adapted to the specific circumstances operating on the premises and should address, apart from animal welfare, aesthetics of the method of euthanasia, cost of the method, operator safety, biosecurity and environmental aspects.

  3. Following the decision to kill the animals, killing should be carried out as quickly as possible, and normal husbandry should be maintained until the animals are killed.

  4. The handling and movement of animals should be minimised and when done, it should be carried out in accordance with the recommendations described below.

  5. Animal restraint should be sufficient to facilitate effective killing, and in accordance with animal welfare and operator safety requirements; when restraint is required, killing should follow with minimal delay.

  6. When animals are killed for disease control purposes, methods used should result in immediate death or immediate loss of consciousness lasting until death; when loss of consciousness is not immediate, induction of unconsciousness should be non-aversive or the least aversive possible and should not cause avoidable anxiety, pain, distress or suffering in animals.

  7. For animal welfare considerations, young animals should be killed before older animals; for biosecurity considerations, infected animals should be killed first, followed by in-contact animals, and then the remaining animals.

  8. There should be continuous monitoring of the procedures by the Competent Authorities to ensure they are consistently effective with regard to animal welfare, operator safety and biosecurity.

  9. When the operational procedures are concluded, there should be a written report describing the practices adopted and their effect on animal welfare, operator safety and biosecurity.

  10. These general principles should also apply when animals need to be killed for other purposes such as after natural disasters or for culling animal populations.


Article 7.6.2.


Organisational structure

Disease control contingency plans should be in place at a national level and should contain details of management structure, disease control strategies and operational procedures; animal welfare considerations should be addressed within these disease control contingency plans. The plans should also include a strategy to ensure that an adequate number of personnel competent in the humane killing of animals is available. Local level plans should be based on national plans and be informed by local knowledge.

Disease control contingency plans should address the animal welfare issues that may result from animal movement controls.

The operational activities should be led by an official Veterinarian who has the authority to appoint the personnel in the specialist teams and ensure that they adhere to the required animal welfare and biosecurity standards. When appointing the personnel, he/she should ensure that the personnel involved have the required competencies.

The official Veterinarian should be responsible for all activities across one or more affected premises and should be supported by coordinators for planning (including communications), operations and logistics to facilitate efficient operations.

The official Veterinarian should provide overall guidance to personnel and logistic support for operations on all affected premises to ensure consistency in adherence to the OIE animal welfare and animal health recommendations.

A specialist team, led by a team leader answerable to the official Veterinarian, should be deployed to work on each affected premises. The team should consist of personnel with the competencies to conduct all required operations; in some situations, personnel may be required to fulfil more than one function. Each team should contain a veterinarian or have access to veterinary advice at all times.

In considering the animal welfare issues associated with killinganimals, the key personnel, their responsibilities and competencies required are described in Article 7.6.3.


Article 7.6.3.


Responsibilities and competencies of the specialist team

  1. Team leader

    1. Responsibilities

      i)
      plan overall operations on affected premises;

      ii)
      determine and address requirements for animal welfare, operator safety and biosecurity;

      iii)
      organise, brief and manage team of people to facilitate humane killing of the relevant animals on the premises in accordance with national regulations and these recommendations;

      iv)
      determine logistics required;

      v)
      monitor operations to ensure animal welfare, operator safety and biosecurity requirements are met;

      vi)
      report upwards on progress and problems;

      vii)
      provide a written report at the conclusion of the killing, describing the practices adopted and their effect on the animal welfare, operator safety and biosecurity outcomes.

    2. Competencies

      i)
      appreciation of normal animal husbandry practices;

      ii)
      appreciation of animal welfare and the underpinning behavioural, anatomical and physiological processes involved in the killing process;

      iii)
      skills to manage all activities on premises and deliver outcomes on time;

      iv)
      awareness of psychological effects on farmer, team members and general public;

      v)
      effective communication skills;

      vi)
      appreciation of the environmental impacts caused by their operation.

  2. Veterinarian

    1. Responsibilities

      i)
      determine and supervise the implementation of the most appropriate killing method to ensure that animals are killed without avoidable pain and distress;

      ii)
      determine and implement the additional requirements for animal welfare, including the order of killing;

      iii)
      ensure that confirmation of the death of the animals is carried out by competent persons at appropriate times after the killing procedure;

      iv)
      minimise the risk of disease spread within and from the premises through the supervision of biosecurity procedures;

      v)
      continuously monitor animal welfare and biosecurity procedures;

      vi)
      in cooperation with the leader, prepare a written report at the conclusion of the killing, describing the practices adopted and their effect on animal welfare.

    2. Competencies

      i)
      ability to assess animal welfare, especially the effectiveness of stunning and killing and to correct any deficiencies;

      ii)
      ability to assess biosecurity risks.

  3. Animal handlers

    1. Responsibilities

      i)
      review on-site facilities in terms of their appropriateness;

      ii)
      design and construct temporary animal handling facilities, when required;

      iii)
      move and restrain animals;

      iv)
      continuously monitor animal welfare and biosecurity procedures.

    2. Competencies

      i)
      animal handling in emergency situations and in close confinement is required;

      ii)
      an appreciation of biosecurity and containment principles.

  4. Animal killing personnel

    1. Responsibilities

      Humane killing of the animals through effective stunning and killing should be ensured.

    2. Competencies

      i)
      when required by regulations, licensed to use necessary equipment;

      ii)
      competent to use and maintain relevant equipment;

      iii)
      competent to use techniques for the species involved;

      iv)
      competent to assess effective stunning and killing.

  5. Carcass disposal personnel

    1. Responsibilities

      An efficient carcass disposal (to ensure killing operations are not hindered) should be ensured.

    2. Competencies

      The personnel should be competent to use and maintain available equipment and apply techniques for the species involved.

  6. Farmer/owner/manager

    1. Responsibilities

      i)
      assist when requested.

    2. Competencies

      i)
      specific knowledge of his/her animals and their environment.


Article 7.6.4.


Considerations in planning the humane killing of animals

Many activities will need to be conducted on affected premises, including the humane killing of animals. The team leader should develop a plan for humanely killinganimals on the premises which should include consideration of:

  1. minimising handling and movement of animals;

  2. killing the animals on the affected premises; however, there may be circumstances where the animals may need to be moved to another location for killing; when the killing is conducted at an abattoir, the recommendations in Chapter 7.5. on the slaughter of animals should be followed;

  3. the species, number, age and size of animals to be killed, and the order of killing them;

  4. methods of killing the animals, and their cost;

  5. housing, husbandry, location of the animals as well as accessibility of the farm;

  6. the availability and effectiveness of equipment needed for killing of the animals, as well as the time necessary to kill the required number of animals using such methods;

  7. the facilities available on the premises that will assist with the killing including any additional facilities that may need to be brought on and then removed from the premises;

  8. biosecurity and environmental issues;

  9. the health and safety of personnel conducting the killing;

  10. any legal issues that may be involved, for example where restricted veterinary drugs or poisons may be used, or where the process may impact on the environment;

  11. the presence of other nearby premises holding animals;

  12. possibilities for removal, disposal and destruction of carcasses.

The plan should minimise the negative welfare impacts of the killing by taking into account the different phases of the procedures to be applied for killing (choice of the killing sites, killing methods, etc.) and the measures restricting the movements of the animals.

Competences and skills of the personnel handling and killinganimals.

In designing a killing plan, it is essential that the method chosen be consistently reliable to ensure that all animals are humanely and quickly killed.


Article 7.6.5.


Table summarising killing methods described in Articles 7.6.6.-7.6.18.

The methods are described in the order of mechanical, electrical and gaseous, not in an order of desirability from an animal welfare viewpoint.

Species Age rangeProcedureRestraint
necessary
Animal welfare concerns with inappropriate applicationArticle
reference
Cattleallfree bulletnonon-lethal woundingArticle 7.6.6.
all except neonatespenetrating captive bolt - followed by pithing or bleedingyesineffective stunningArticle 7.6.7.
adults onlynon-penetrating captive bolt, followed by bleedingyesineffective stunning, regaining of consciousness before killingArticle 7.6.8.
calves onlyelectrical, two-stage application yespain associated with cardiac arrest after ineffective stunning Article 7.6.10.
calves onlyelectrical, single application (method 1)yesineffective stunningArticle 7.6.11.
allinjection with barbiturates and other drugsyesnon-lethal dose, pain associated with injection siteArticle 7.6.15.
Sheep and goatsallfree bulletnonon-lethal woundingArticle 7.6.6.
all except neonates penetrating captive bolt, followed by pithing or bleedingyesineffective stunning, regaining of consciousness before deathArticle 7.6.7.
all except neonates non-penetrating captive bolt, followed by bleeding yesineffective stunning, regaining of consciousness before deathArticle 7.6.8.
neonatesnon-penetrating captive boltyesnon-lethal woundingArticle 7.6.8.
allelectrical, two-stage application yespain associated with cardiac arrest after ineffective stunningArticle 7.6.10.
allelectrical, single application (method 1)yesineffective stunningArticle 7.6.11.
neonates onlyCO2 / air mixtureyesslow induction of unconsciousness, aversiveness of induction Article 7.6.12.
neonates onlynitrogen and/or inert gas mixed with CO2yesslow induction of unconsciousness, aversiveness of inductionArticle 7.6.13.
neonates onlynitrogen and/or inert gasesyesslow induction of unconsciousnessArticle 7.6.14.
allinjection of barbiturates and other drugsyesnon-lethal dose, pain associated with injection siteArticle 7.6.15.
Pigsall, except neonatesfree bulletnonon-lethal woundingArticle 7.6.6.
all except neonatespenetrating captive bolt, followed by pithing or bleedingyesineffective stunning, regaining of consciousness before deathArticle 7.6.7.
neonates onlynon-penetrating captive bolt yesnon-lethal woundingArticle 7.6.8.
all1.electrical, two-stage application yespain associated with cardiac arrest after ineffective stunningArticle 7.6.10.
allelectrical, single application (method 1)yesineffective stunningArticle 7.6.11.
neonates onlyCO2 / air mixtureyesslow induction of unconsciousness,
aversiveness of induction
Article 7.6.12.
neonates onlynitrogen and/or inert gas mixed with CO2yesslow induction of unconsciousness,
aversiveness of induction
Article 7.6.13.
neonates onlynitrogen and/or inert gasesyesslow induction of unconsciousnessArticle 7.6.14.
allinjection with barbiturates and other yesnon-lethal dose, pain associated with injection siteArticle 7.6.15.
Poultryadults onlynon-penetrating captive bolt yesineffective stunningArticle 7.6.8.
day-olds and eggs onlymacerationnonon-lethal wounding, non- immediacyArticle 7.6.9.
adults onlyelectrical, single application (method 2)yesineffective stunningArticle 7.6.11.
adults onlyelectrical, single application, followed by killing (method 3)yesineffective stunning; regaining of consciousness before death Article 7.6.11.
allCO2 / air mixture
Method 1
Method 2
 
 
yes
no
slow induction of unconsciousness, aversiveness of inductionArticle 7.6.12.
allnitrogen and/or inert gas mixed with CO2yesslow induction of unconsciousness, aversiveness of inductionArticle 7.6.13.
allnitrogen and/or inert gasesyesslow induction of unconsciousnessArticle 7.6.14.
allinjection of barbiturates and other drugsyesnon-lethal dose, pain associated with injection siteArticle 7.6.15.
allcervical dislocationnoPoint 1 of 7.6.17.
alldecapitationnoPoint 2 of 7.6.17.
adults onlyaddition of anaesthetics to feed or water, followed by an appropriate killing methodnoineffective or slow induction of unconsciousnessArticle 7.6.16.

Article 7.6.6.


Free bullet

  1. Introduction

    1. A free bullet is a projectile fired from a shotgun, rifle, handgun or purpose-made humane killer.

    2. The most commonly used firearms for close range use are:

      i)
      humane killers (specially manufactured/adapted single-shot weapons);

      ii)
      shotguns (12, 16, 20, 28 bore and .410);

      iii)
      rifles (.22 rimfire);

      iv)
      handguns (various calibres from .32 to .45).

    3. The most commonly used firearms for long range use are rifles (.22, .243, .270 and .308).

    4. A free bullet used from long range should be aimed to penetrate the skull or soft tissue at the top of the neck of the animals (high neck shot) and to cause irreversible concussion and death and should only be used by properly trained and competent marksmen.

  2. Requirements for effective use

    1. The marksman should take account of human safety in the area in which he/she is operating. Appropriate vision and hearing protective devices should be worn by all personnel involved.

    2. The marksman should ensure that the animal is not moving and in the correct position to enable accurate targeting and the range should be as short as possible (5–50 cm for a shotgun) but the barrel should not be in contact with the head of the animals.

    3. The correct cartridge, calibre and type of bullet for the different species age and size should be used. Ideally, the ammunition should expand upon impact and dissipate its energy within the cranium.

    4. Shot animals should be checked to ensure the absence of brain stem reflexes.

  3. Advantages

    1. Used properly, a free bullet provides a quick and effective method for killing.

    2. It requires minimal or no restraint and can be use to kill from a distance by properly trained and competent marksmen.

    3. It is suitable for killing agitated animals in open spaces.

  4. Disadvantages

    1. The method is potentially dangerous to humans and other animals in the area.

    2. It has the potential for non-lethal wounding.

    3. Destruction of brain tissue may preclude diagnosis of some diseases.

    4. Leakage of bodily fluids may present a biosecurity risk.

    5. Legal requirements may preclude or restrict use.

    6. There is a limited availability of competent personnel.

  5. Conclusion

    The method is suitable for cattle, sheep, goats and pigs, including large animals in open spaces.

Figure 1. The optimum shooting position for cattle is at the intersection of two imaginary lines drawn from the rear of the eyes to the opposite horn buds.

image

Figure source: Humane Slaughter Association (2005) Guidance Notes No. 3: Humane Killing of Livestock Using Firearms. Published by the Humane Slaughter Association, The Old School, Brewhouse Hill, Wheathampstead, Hertfordshire AL4 8AN, United Kingdom (www.hsa.org.uk).

Figure 2. The optimum position for hornless sheep and goats is on the midline.

image

Figure source: Humane Slaughter Association (2005) Guidance Notes No. 3: Humane Killing of Livestock Using Firearms. Published by the Humane Slaughter Association, The Old School, Brewhouse Hill, Wheathampstead, Hertfordshire AL4 8AN, United Kingdom (www.hsa.org.uk).

Figure 3. The optimum shooting position for heavily horned sheep and horned goats is behind the poll aiming towards the angle of the jaw.

image

Figure Source: Humane Slaughter Association (2005) Guidance Notes No. 3: Humane Killing of Livestock Using Firearms. Published by the Humane Slaughter Association, The Old School, Brewhouse Hill, Wheathampstead, Hertfordshire AL4 8AN, United Kingdom (www.hsa.org.uk).

Figure 4. The optimum shooting position for pigs is just above eye level, with the shot directed down the line of the spinal cord.

image

Figure source: Humane Slaughter Association (2005) Guidance Notes No. 3: Humane Killing of Livestock Using Firearms. Published by the Humane Slaughter Association, The Old School, Brewhouse Hill, Wheathampstead, Hertfordshire AL4 8AN, United Kingdom (www.hsa.org.uk).


Article 7.6.7.


Penetrating captive bolt

  1. Introduction

    A penetrating captive bolt is fired from a gun powered by either compressed air or a blank cartridge. There is no free projectile.

    The captive bolt should be aimed on the skull in a position to penetrate the cortex and mid-brain of the animal. The impact of the bolt on the skull produces unconsciousness. Physical damage to the brain caused by penetration of the bolt may result in death; however, pithing or bleeding should be performed as soon as possible after the shot to ensure the death of the animal. Shooting poultry species with the captive bolts results in immediate destruction of the skull and brain, causing death. For a detailed description on the use of this method, see Chapter 7.5.

  2. Requirements for effective use

    1. For cartridge powered and compressed air guns, the bolt velocity and the length of the bolt should be appropriate to the species and type of animal, in accordance with the recommendations of the manufacturer.

    2. Captive bolt guns should be frequently cleaned and maintained in good working condition.

    3. More than one gun may be necessary to avoid overheating, and a back-up gun should be available in the event of an ineffective shot.

    4. Animals should be restrained; at a minimum, they should be penned for cartridge powered guns and in a race for compressed air guns.

    5. The operator should ensure that the head of the animal is accessible.

    6. The operator should fire the captive bolt at right angles to the skull in the optimal position (see figures 1, 3 & 4. The optimum shooting position for hornless sheep is on the highest point of the head, on the midline and aim towards the angle of the jaw).

    7. To ensure the death of the animal, pithing or bleeding should be performed as soon as possible after stunning.

    8. Animals should be monitored continuously after stunning until death to ensure the absence of brain stem reflexes.

  3. Advantages

    1. Mobility of cartridge powered equipment reduces the need to move animals.

    2. The method induces an immediate onset of a sustained period of unconsciousness.

  4. Disadvantages

    1. Poor gun maintenance and misfiring, and inaccurate gun positioning and orientation may result in poor animal welfare.

    2. Post stun convulsions may make pithing difficult and hazardous.

    3. The method is difficult to apply in agitated animals.

    4. Repeated use of a cartridge powered gun may result in over-heating.

    5. Leakage of bodily fluids may present a biosecurity risk.

    6. Destruction of brain tissue may preclude diagnosis of some diseases.

  5. Conclusions

    The method is suitable for poultry, cattle, sheep, goats and pigs (except neonates), when followed by pithing or bleeding.


Article 7.6.8.


Non-penetrating captive bolt

  1. Introduction

    A non-penetrating captive bolt is fired from a gun powered by either compressed air or a blank cartridge. There is no free projectile.

    The gun should be placed on the front of the skull to deliver a percussive blow which produces unconsciousness in cattle (adults only), sheep, goats and pigs, and death in poultry and neonate sheep, goats and pigs. Bleeding should be performed as soon as possible after the blow to ensure the death of the animal.

  2. Requirements for effective use

    1. For cartridge powered and compressed air guns, the bolt velocity should be appropriate to the species and type of animal, in accordance with the recommendations of the manufacturer.

    2. Captive bolt guns should be frequently cleaned and maintained in good working condition.

    3. More than one gun may be necessary to avoid overheating, and a back-up gun should be available in the event of an ineffective shot.

    4. Animals should be restrained; at a minimum mammals should be penned for cartridge powered guns and in a race for compressed air guns; birds should be restrained in cones, shackles, crushes or by hand.

    5. The operator should ensure that the head of the animal is accessible.

    6. The operator should fire the captive bolt at right angles to the skull in the optimal position (figures 1– 4).

    7. To ensure death in non-neonate mammals, bleeding should be performed as soon as possible after stunning.

    8. Animals should be monitored continuously after stunning until death to ensure the absence of brain stem reflexes.

  3. Advantages

    1. The method induces an immediate onset of unconsciousness, and death in birds and neonates.

    2. Mobility of equipment reduces the need to move animals.

  4. Disadvantages

    1. As consciousness can be regained quickly in non-neonate mammals, they should be bled as soon as possible after stunning.

    2. Laying hens in cages have to be removed from their cages and most birds have to be restrained.

    3. Poor gun maintenance and misfiring, and inaccurate gun positioning and orientation may result in poor animal welfare.

    4. Post stun convulsions may make bleeding difficult and hazardous.

    5. Difficult to apply in agitated animals; such animals may be sedated in advance of the killing procedure.

    6. Repeated use of a cartridge powered gun may result in over-heating.

    7. Bleeding may present a biosecurity risk.

  5. Conclusions

    The method is suitable for killing poultry, and neonate sheep, goats and pigs up to a maximum weight of 10 kg.


Article 7.6.9.


Maceration

  1. Introduction

    Maceration, utilising a mechanical apparatus with rotating blades or projections, causes immediate fragmentation and death in day-old poultry and embryonated eggs.

  2. Requirements

    1. Maceration requires specialised equipment which should be kept in excellent working order.

    2. The rate of introducing the birds should not allow the equipment to jam, birds to rebound from the blades or the birds to suffocate before they are macerated.

  3. Advantages

    1. Procedure results in immediate death.

    2. Large numbers can be killed quickly.

  4. Disadvantages

    1. Specialised equipment is required.

    2. Macerated tissues may present biosecurity or human health risks.

    3. The cleaning of the equipment can be a source of contamination.

  5. Conclusion

    The method is suitable for killing day-old poultry and embryonated eggs.


Article 7.6.10.


Electrical – two-stage application

  1. Introduction

    A two-stage application of electric current comprises firstly an application of current to the head by scissor-type tongs, immediately followed by an application of the tongs across the chest in a position that spans the heart.

    The application of sufficient electric current to the head will induce ‘tonic/clonic’ epilepsy and unconsciousness. Once the animal is unconscious, the second stage will induce ventricular fibrillation (cardiac arrest) resulting in death. The second stage (the application of low frequency current across the chest) should only be applied to unconscious animals to prevent unacceptable levels of pain.

  2. Requirements for effective use

    1. The stunner control device should generate a low frequency (AC sine wave 50 Hz) current with a minimum voltage and current as set out in the following table:

      AnimalMinimum voltage (V)Minimum current (A)
      Cattle2201.5
      Sheep2201.0
      Pigs over 6 weeks of age2201.3
      Pigs less than 6 weeks of age1250.5
    2. Appropriate protective clothing (including rubber gloves and boots) should be worn.

    3. Animals should be restrained, at a minimum free-standing in a pen, close to an electrical supply.

    4. Two team members are required, the first to apply the electrodes and the second to manipulate the position of the animal to allow the second application to be made.

    5. A stunning current should be applied via scissor-type stunning tongs in a position that spans the brain for a minimum of 3 seconds; immediately following the application to the head, the electrodes should be transferred to a position that spans the heart and the electrodes applied for a minimum of 3 seconds.

    6. Electrodes should be cleaned regularly and after use, to enable optimum electrical contact to be maintained.

    7. Animals should be monitored continuously after stunning until death to ensure the absence of brain stem reflexes.

    8. Electrodes should be applied firmly for the intended duration of time and pressure not released until the stun is complete.

  3. Advantages

    1. The application of the second stage minimises post-stun convulsions and therefore the method is particularly effective with pigs.

    2. Non-invasive technique minimises biosecurity risk.

  4. Disadvantages

    1. The method requires a reliable supply of electricity.


    2. The electrodes should be applied and maintained in the correct positions to produce an effective stun and kill.

    3. Most stunner control devices utilise low voltage impedance sensing as an electronic switch prior to the application of high voltages; in unshorn sheep, contact impedance may be too high to switch on the required high voltage (especially during stage two).

    4. The procedure may be physically demanding, leading to operator fatigue and poor electrode placement.

  5. Conclusion

    The method is suitable for calves, sheep and goats, and especially for pigs (over one week of age).

Figure 5. Scissor-type tongs.

image


Article 7.6.11.


Electrical – single application

  1. Method 1

    Method 1 comprises the single application of sufficient electrical current to the head and back, to simultaneously stun the animal and fibrillate the heart. Provided sufficient current is applied in a position that spans both the brain and heart, the animal will not recover consciousness.

    1. Requirements for effective use

      i)
      The stunner control device should generate a low frequency (30–60 Hz) current with a minimum voltage of 250 volts true RMS under load.

      ii)
      Appropriate protective clothing (including rubber gloves and boots) should be worn.

      iii)
      Animals should be individually and mechanically restrained close to an electrical supply as the maintenance of physical contact between the stunning electrodes and the animal is necessary for effective use.

      iv)
      The rear electrode should be applied to the back, above or behind the heart, and then the front electrode in a position that is forward of the eyes, with current applied for a minimum of 3 seconds.

      v)
      Electrodes should be cleaned regularly between animals and after use, to enable optimum electrical contact to be maintained.

      vi)
      Water or saline may be necessary to improve electrical contact with sheep.

      vii)
      An effective stun and kill should be verified by the absence of brain stem reflexes.

    2. Advantages

      i)
      Method 1 stuns and kills simultaneously.

      ii)
      It minimises post-stun convulsions and therefore is particularly effective with pigs.

      iii)
      A single team member only is required for the application.

      iv)
      Non-invasive technique minimises biosecurity risk.

    3. Disadvantages

      i)
      Method 1 requires individual mechanical animal restraint.

      ii)
      The electrodes should be applied and maintained in the correct positions to produce an effective stun and kill.

      iii)
      Method 1 requires a reliable supply of electricity.

    4. Conclusion

      Method 1 is suitable for calves, sheep, goats, and pigs (over one week of age).

  2. Method 2

    Method 2 stuns and kills by drawing inverted and shackled poultry through an electrified waterbath stunner. Electrical contact is made between the ‘live’ water and earthed shackle and, when sufficient current is applied, poultry will be simultaneously stunned and killed.

    1. Requirements for effective use

      i)
      A mobile waterbath stunner and a short loop of processing line are required.

      ii)
      A low frequency (50–60 Hz) current applied for a minimum of 3 seconds is necessary to stun and kill the birds.

      iii)
      Poultry need to be manually removed from their cage, house or yard, inverted and shackled onto a line which conveys them through a waterbath stunner with their heads fully immersed.

      iv)
      The required minimum currents to stun and kill dry birds are:

      • Quails – 100 mA/bird

      • Chickens – 160 mA/bird

      • Ducks & geese – 200 mA/bird

      • Turkeys – 250 mA/bird.

      A higher current is required for wet birds.

      v)
      An effective stun and kill should be verified by the absence of brain stem reflexes.

    2. Advantages

      i)
      Method 2 stuns and kills simultaneously.

      ii)
      It is capable of processing large numbers of birds reliably and effectively.

      iii)
      This non-invasive technique minimises biosecurity risk.

    3. Disadvantages

      i)
      Method 2 requires a reliable supply of electricity.

      ii)
      Handling, inversion and shackling of birds are required.

    4. Conclusion

      Method 2 is suitable for large numbers of poultry.

  3. Method 3

    Method 3 comprises the single application of sufficient electrical current to the head of poultry in a position that spans the brain, causing unconsciousness; this is followed by a killing method (see Article 7.6.17.).

    1. Requirements for effective use

      i)
      The stunner control device should generate sufficient current (more than 600 mA/duck and more than 300 mA/bird) to stun.

      ii)
      Appropriate protective clothing (including rubber gloves and boots) should be worn.

      iii)
      Birds should be restrained, at a minimum manually, close to an electrical supply.

      iv)
      Electrodes should be cleaned regularly and after use, to enable optimum electrical contact to be maintained.

      v)
      Birds should be monitored continuously after stunning until death to ensure the absence of brain stem reflexes.

    2. Advantages

      Non-invasive technique (when combined with cervical dislocation) minimises biosecurity risk.

    3. Disadvantages

      i)
      Method 3 requires a reliable supply of electricity and is not suitable for large-scale operations.

      ii)
      The electrodes should be applied and maintained in the correct position to produce an effective stun.

      iii)
      Birds should be individually restrained.

      iv)
      It should be followed by a killing method.

    4. Conclusion

      Method 3 is suitable for small numbers of poultry.


Article 7.6.12.


CO2 / air mixture

  1. Introduction

    Controlled atmosphere killing is performed by exposing animals to a predetermined gas mixture, either by placing them in a gas-filled container or apparatus (Method 1) or by placing transport modules or crates containing birds in a gas tight container and introducing a gas mixture (Method 2) or by the gas being introduced into a poultry house (Method 3). Method 3 should be used whenever possible, as it eliminates welfare issues resulting from the need to manually remove live birds. Although Method 2 requires handling and crating of the birds, it benefits bird welfare overall in comparison with Method 1 as it reduces the risk of death by smothering or suffocation.

    Inhalation of carbon dioxide (CO2) induces respiratory and metabolic acidosis and hence reduces the pH of cerebrospinal fluid (CSF) and neurones thereby causing unconsciousness and, after prolonged exposure, death. Exposure to carbon dioxide does not induce immediate loss of consciousness, therefore the aversive nature of gas mixtures containing high concentrations of CO2 and the respiratory distress occurring during the induction phase are important considerations for animal welfare.

  2. Method 1

    The animals are placed in a gas-filled container or apparatus.

    1. Requirements for effective use in a container or apparatus

      i)
      Containers or apparatus should allow the required gas concentration to be maintained and accurately measured.

      ii)
      When animals are exposed to the gas individually or in small groups in a container or apparatus, the equipment used should be designed, constructed, and maintained in such a way as to avoid injury to the animals and allow them to be observed.

      iii)
      Animals can also be introduced to low concentrations (as low concentrations are not aversive) and the concentration could be increased afterwards and the animals then held in the higher concentration until death is confirmed.

      iv)
      Team members should ensure that there is sufficient time allowed for each batch of animals to die before subsequent ones are introduced into the container or apparatus.

      v)
      Containers or apparatus should not be overcrowded and measures are needed to avoid animals suffocating by climbing on top of each other.

    2. Advantages

      i)
      CO2 is readily available.

      ii)
      Application methods are simple.

      iii)
      The volume of gas required can be readily calculated.

      iv)
      As the units are operated outdoor, the gas is dispersed quickly at the end of each cycle by opening the door, improving operator’s health and safety.

      v)
      The system uses skilled catching teams and equipment in daily use by the industry.

      vi)
      Metal containers can be readily cleansed and disinfected.

    3. Disadvantages

      i)
      The need for properly designed container or apparatus.

      ii)
      The aversive nature of high CO2 concentrations.

      iii)
      No immediate loss of consciousness.

      iv)
      The risk of suffocation due to overcrowding.

      v)
      Difficulty in verifying death while the animals are in the container or apparatus.

    4. Conclusion

      Method 1 is suitable for use in poultry, and neonatal sheep, goats and pigs.

  3. Method 2

    In this method, the crates or modules holding the birds are loaded into a chamber into which gas is introduced. As illustrated in the example below, a containerised gassing unit (CGU) typically comprises a gas-tight chamber designed to accommodate poultry transport crates or a single module. The chamber is fitted with gas lines and diffusers, with silencers that are connected via a system of manifolds and gas regulators to gas cylinders. There is a hole at the top to permit displaced air to escape when the container is filling with gas.

    The procedures for the operation of CGU include (a) position the container on level, solid, open ground; (b) connect the gas cylinder to the container (c) load birds into the container (d) shut and secure the door, (e) deliver the gas until a concentration of 45 percent by volume of carbon dioxide has been achieved at the top of the container, (f) allow time for the birds to become unconscious and die (g) open the door and allow gas to be dispersed in the air (h) remove the module (i) check each drawer for survivors (j) humanely kill any survivors; and (k) dispose of carcasses appropriately.

    1. Requirements for effective use of containerised gassing units (CGU)

      i)
      The birds should be caught gently and placed in crates or modules of appropriate size and at appropriate stocking densities to allow all birds to sit down.

      ii)
      The crates or module full of birds should be placed inside the container and the door shut only when the operator is ready to administer the gas.

      iii)
      Ensure the container door is locked and administer the gas until a minimum concentration of 45 percent carbon dioxide is achieved at the top of the crates.

      iv)
      An appropriate gas meter should be used to ensure the appropriate concentration of carbon dioxide is achieved and maintained until it can be confirmed that the birds have been killed.

      v)
      Sufficient exposure time should be allowed for birds to die before the door is opened. In the absence of a viewing window that allows direct observation of birds during killing, cessation of vocalisation and convulsive wing flapping sounds, which can be listened to by standing near the container, can be used to determine that the birds are unconscious and that death is imminent. Remove the crates or modules from the container and leave them in the open air.

      vi)
      Each crate or module should be examined and birds checked to ensure they are dead. Dilated pupils and absence of breathing indicate death.

      vii)
      Any survivors should be humanely killed.

      viii)
      Ducks and geese are resilient to the effects of carbon dioxide and therefore require a minimum of 80 percent CO2 and a longer period of exposure to die.

    2. Advantages

      i)
      The gas is introduced quickly and quietly resulting in less turbulence and disturbance to the birds.

      ii)
      Gradual increase in the concentration of CO2 minimises the aversive nature of this method for inducing unconsciousness.

      iii)
      The use of transport crates or modules to move birds minimises handling. Birds should be handled by trained, experienced catching teams at the time of depopulation of the poultry house.

      iv)
      The modules are loaded mechanically into the CGU and a lethal mixture of gas is rapidly introduced into the chamber immediately after sealing.

      v)
      CO2 is readily available.

      vi)
      Birds are exposed to gas more uniformly and they do not smother each other when compared with Method 1.

      vii)
      The volume of gas required can be readily calculated.

      viii)
      As the units are operated outdoors, the gas is dispersed quickly at the end of each cycle by opening the door, improving operator’s health and safety.

      ix)
      The system uses skilled catching teams and equipment in daily use by the industry.

      x)
      Metal containers can be readily cleansed and disinfected.

    3. Disadvantages

      i)
      Requires trained operators, trained catchers, transport modules and fork lift. However, this equipment and suitable areas with hard surfaces are usually available.

      ii)
      The main limiting factors are speed of catching birds.

      iii)
      In the absence of a viewing window, visual confirmation of death while the birds are still in the container is difficult. However, cessation of vocalisation and convulsive wing flapping sounds can be used to determine onset of death.

    4. Conclusion

      i)
      Method 2 is suitable for use in a wide range of poultry systems, providing there is access to vehicles to carry the containers and equipment.

      ii)
      Birds should be introduced into the container or apparatus, which is then sealed and filled as quickly as possible with the required gas concentrations, i.e. more than 40 percent CO2. Birds are held in this atmosphere until death is confirmed.

      iii)
      Method 2 is suitable for use in poultry, and neonatal sheep, goats and pigs. However, CO2 is likely to cause a period of distress in the animals before they lose consciousness.

  4. Method 3

    The gas is introduced into a poultry house.

    1. Requirements for effective use in a poultry house

      i)
      Prior to introduction of the CO2, the poultry house should be appropriately sealed to allow control over the gas concentration. The interval between sealing and gas administration should be kept to the minimum so as to avoid overheating.

      Forced ventilation systems, where fitted, should only be switched off immediately prior to gas administration.

      The main water supply to the poultry house may have to be turned off and water drained to avoid freezing and bursting of water pipes.

      Feeders and water troughs should be lifted to avoid obstruction of the gas entry and prevent injury to birds.

      ii)
      Gas delivery pipes or lancets should be positioned appropriately such that birds are not hit directly by very cold gas delivered at high pressures. It may be necessary to exclude birds from the area in front of the delivery pipes, for a distance of about 20 meters, by partitioning the house with nets, wire mesh or similarly perforated materials.

      iii)
      The house should be gradually filled with CO2 so that all birds are exposed to a concentration of >40 percent until they are dead; a vaporiser may be required to prevent freezing.

      iv)
      Devices should be used to accurately measure the gas concentration at the maximum height accommodation of birds.

    2. Advantages

      i)
      Applying gas to birds in situ eliminates the need to manually remove live birds.

      ii)
      CO2 is readily available.

      iii)
      Gradual raising of CO2 concentration minimises the aversiveness of the induction of unconsciousness.

    3. Disadvantages

      i)
      It is difficult to determine volume of gas required to achieve adequate concentrations of CO2 in some poultry houses.

      ii)
      It is difficult to verify death while the birds are in the poultry house.

      The extremely low temperature of liquid CO2 entering the house and formation of solid CO2 (dry ice) may cause concern for bird welfare.

    4. Conclusion

      Method 3 is suitable for use in poultry in closed-environment sheds. This method could be developed for killing pigs. However, CO2 is likely to cause a period of distress in the birds before they lose consciousness.


Article 7.6.13.


Nitrogen and/or inert gas mixed with CO2

  1. Introduction

    CO2 may be mixed in various proportions with nitrogen or an inert gas (e.g. argon), and the inhalation of such mixtures leads to hypercapnic-hypoxia and death when the oxygen concentration by volume is <2 percent, or <5 percent for chickens. Various mixtures of CO2 and nitrogen or an inert gas can be administered to kill birds using Methods 1 and 2 described under Article 7.6.12. Whole house gassing with mixtures of CO2 and nitrogen, or an inert gas, has not been tested owing to the complex issues presented by mixing gases in large quantities. Such mixtures however do not induce immediate loss of consciousness, therefore the aversiveness of various gas mixtures containing high concentrations of CO2 and the respiratory distress occurring during the induction phase, are important animal welfare considerations.

    Pigs and poultry appear not to find low concentrations of CO2 strongly aversive, and a mixture of nitrogen or argon with <30 percent CO2 by volume and <2 percent O2 by volume can be used for killing poultry, neonatal sheep, goats and pigs.

  2. Method 1

    The animals are placed in a gas-filled container or apparatus.

    1. Requirements for effective use

      i)
      Containers or apparatus should allow the required gas concentrations to be maintained, and the O2 and CO2 concentrations accurately measured during the killing procedure.

      ii)
      When animals are exposed to the gases individually or in small groups in a container or apparatus, the equipment used should be designed, constructed, and maintained in such a way as to avoid injury to the animals and allow them to be observed.

      iii)
      Animals should be introduced into the container or apparatus after it has been filled with the required gas concentrations (with <2 percent O2), and held in this atmosphere until death is confirmed.

      iv)
      Team members should ensure that there is sufficient time allowed for each batch of animals to die before subsequent ones are introduced into the container or apparatus.

      v)
      Containers or apparatus should not be overcrowded and measures are needed to avoid animals suffocating by climbing on top of each other.

    2. Advantages

      Low concentrations of CO2 cause little aversiveness and, in combination with nitrogen or an inert gas, produces a fast induction of unconsciousness.

    3. Disadvantages

      i)
      A properly designed container or apparatus is needed.

      ii)
      It is difficult to verify death while the animals are in the container or apparatus.

      iii)
      There is no immediate loss of consciousness.

      iv)
      Exposure times required to kill are considerable.

    4. Conclusion

      The method is suitable for poultry, and for neonatal sheep, goats and pigs.

  3. Method 2

    In this method, the crates or modules holding the birds are loaded into a container and gas is introduced into the container (refer to Figures under Article 7.6.12.). As shown in the example below, each containerised gassing unit (CGU) typically comprises a gas-tight chamber designed to accommodate poultry transport crates or a module. The container or chamber is fitted with gas lines and diffusers, with silencers, which in turn are connected via a system of manifolds and gas regulators to gas cylinders. There is a hole at the top of the unit to permit displaced air to escape when filling the container with gas.

    Procedures involved in the operation of CGU includes (a) position the container on a level, solid, open ground; (b) connect gas cylinder to the container (c) load a module of birds into the container, (d) shut and secure the door, (e) deliver the gas to the point where less than 2 percent by volume of oxygen is found at the top of the container, (f) allow time for the birds to become unconscious and die, (g) open the door and allow the gas to be dispersed in air, (h) remove the module, (i) check each drawer for survivors; (j) humanely kill survivors, if any; and (k) dispose carcasses appropriately.

    1. Requirements for effective use of containerised gassing units (CGU)

      i)
      The birds should be caught gently and placed in crates or modules of appropriate size and at appropriate stocking densities to allow all birds to sit down.

      ii)
      The crates or module of birds should be placed inside the container and the door shut only when the operator is ready to administer the gas mixture.

      iii)
      Ensure the container door is locked and administer the gas mixture until <2 percent residual oxygen is achieved at the top of the crates.

      iv)
      An appropriate gas meter should be used to ensure a concentration of oxygen <2 percent is achieved and maintained until it can be confirmed that the birds have been killed.

      v)
      Sufficient exposure time should be allowed for birds to die before the door is opened. In the absence of a viewing window, which allows direct observation of birds during killing, cessation of vocalisation and wing flapping sounds can be observed by standing close to the container and used to determine the onset of death in birds. Remove the crates or modules from the container and leave them in the open air.

      vi)
      Each crate or module should be examined and birds checked to ensure they are dead. Dilated pupils and absence of breathing movements indicate death.

      vii)
      Any survivors should be humanely killed.

      viii)
      Ducks and geese do not appear to be resilient to the effects of a mixture of 20 percent carbon dioxide and 80 percent nitrogen or argon.

    2. Advantages

      i)
      The gas mixture is introduced quickly and quietly resulting in less turbulence and disturbance to the birds.

      ii)
      The use of transport crates or modules to move birds minimises handling. Birds should be handled by trained, experienced catching teams at the time of depopulation of the poultry house.

      iii)
      The modules are loaded mechanically into the CGU and a lethal mixture of gas is rapidly introduced into the chamber immediately after sealing.

      iv)
      Mixtures containing up to 20 percent carbon dioxide in argon are readily available as welding gas cylinders.

      v)
      Birds are exposed to gas in a more uniform manner and they do not smother each other when compared with Method 1.

      vi)
      Two CGU can be operated in tandem and throughputs of up to 4,000 chickens per hour are possible.

      vii)
      The volume of gas required can be readily calculated.

      viii)
      As the units are operated outdoor the gas is dispersed quickly at the end of each cycle by opening the door, improving operators’ health and safety.

      ix)
      The system uses skilled catching teams and equipment in daily use by the industry.

      x)
      Metal containers can be readily cleansed and disinfected.

    3. Disadvantages

      i)
      Requires trained operators, trained catchers, transport modules and a fork lift. However, such equipment and suitable outdoor areas with a hard surface are usually available.

      ii)
      The main limiting factors are speed of catching birds and availability of gas mixtures.

      iii)
      In the absence of a viewing window, visual confirmation of death while the birds are still in the container is difficult. However, cessation of vocalisation and convulsive wing flapping can be used to determine the onset of death.

      iv)
      CGU could be used to kill poultry on small to medium farms, e.g. up to 25 thousand birds on a single farm.

    4. Conclusion

      i)
      Method 2 is suitable for use in poultry and in neonatal sheep, goats and pigs.

      ii)
      Method 2 is suitable for use in poultry in a wide range of poultry systems providing that these have access to vehicles to carry containers and equipment.

      iii)
      Animals should be introduced into the container or apparatus, which is then sealed and filled as quickly as possible with the gas mixture. A residual oxygen concentration of less than 2 percent should be achieved and maintained and birds should be held in this atmosphere until death is confirmed.

image

image

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Figure source: Department of Clinical Veterinary Science, University of Bristol, United Kingdom.


Article 7.6.14.


Nitrogen and/or inert gases

  1. Introduction

    This method involves the introduction of animals into a container or apparatus containing nitrogen or an inert gas such as argon. The controlled atmosphere produced leads to unconsciousness and death from hypoxia.

    Research has shown that hypoxia is not aversive to pigs and poultry, and it does not induce any signs of respiratory distress prior to loss of consciousness.

  2. Requirements for effective use

    1. Containers or apparatus should allow the required gas concentrations to be maintained, and the O2 concentration accurately measured.

    2. When animals are exposed to the gases individually or in small groups in a container or apparatus, the equipment used should be designed, constructed, and maintained in such a way as to avoid injury to the animals and allow them to be observed.

    3. Animals should be introduced into the container or apparatus after it has been filled with the required gas concentrations (with <2 percent O2), and held in this atmosphere until death is confirmed.

    4. Team members should ensure that there is sufficient time allowed for each batch of animals to die before subsequent ones are introduced into the container or apparatus.

    5. Containers or apparatus should not be overcrowded, and measures are needed to avoid animals suffocating by climbing on top of each other.

  3. Advantages

    Animals are unable to detect nitrogen or inert gases, and the induction of hypoxia by this method is not aversive to animals.

  4. Disadvantages

    1. A properly designed container or apparatus is needed.

    2. It is difficult to verify death while the animals are in the container or apparatus.

    3. There is no immediate loss of consciousness.

    4. Exposure times required to kill are considerable.

  5. Conclusion

    The method is suitable for poultry and neonatal sheep, goats and pigs.


Article 7.6.15.


Lethal injection

  1. Introduction

    A lethal injection using high doses of anaesthetic and sedative drugs causes CNS depression, unconsciousness and death. In practice, barbiturates in combination with other drugs are commonly used.

  2. Requirements for effective use

    1. Doses and routes of administration that cause rapid loss of consciousness followed by death should be used.

    2. Prior sedation may be necessary for some animals.

    3. Intravenous administration is preferred, but intraperitoneal or intramuscular administration may be appropriate, especially if the agent is non-irritating.

    4. Animals should be restrained to allow effective administration.

    5. Animals should be monitored to ensure the absence of brain stem reflexes.

  3. Advantages

    1. The method can be used in all species.

    2. Death can be induced smoothly.

  4. Disadvantages

    1. Restraint and/or sedation may be necessary prior to injection.

    2. Some combinations of drug type and route of administration may be painful, and should only be used in unconscious animals.

    3. Legal requirements and skill/training required may restrict use to veterinarians.

    4. Contaminated carcasses may present a risk to other wild animals or domestic animals.

  5. Conclusion

    The method is suitable for killing small numbers of cattle, sheep, goats, pigs and poultry.


Article 7.6.16.


Addition of anaesthetics to feed or water

  1. Introduction

    An anaesthetic agent which can be mixed with poultry feed or water may be used to kill poultry in houses. Poultry which are only anaesthetised need to be killed by another method such as cervical dislocation.

  2. Requirements for effective use

    1. Sufficient quantities of anaesthetic need to be ingested rapidly for effective response.

    2. Intake of sufficient quantities is facilitated if the birds are fasted or water is withheld.

    3. Should be followed by killing (see Article 7.6.17.) if birds are anaesthetised only.

  3. Advantages

    1. Handling is not required until birds are anaesthetised.

    2. There may be biosecurity advantages in the case of large numbers of diseased birds.

  4. Disadvantages

    1. Non-target animals may accidentally access the medicated feed or water when provided in an open environment.

    2. Dose taken is unable to be regulated and variable results may be obtained.

    3. Animals may reject adulterated feed or water due to illness or adverse flavour.

    4. The method may need to be followed by killing.

    5. Care is essential in the preparation and provision of treated feed or water, and in the disposal of uneaten treated feed/water and contaminated carcasses.

  5. Conclusion

    The method is suitable for killing large numbers of poultry in houses. However, a back-up method should be available to kill birds that are anaesthetized but not killed.


Article 7.6.17.


Cervical dislocation and decapitation

  1. Cervical dislocation (manual and mechanical)

    1. Introduction

      Unconscious poultry may be killed by either manual or mechanical cervical dislocation (stretching the neck). This method results in death from cerebral anoxia due to cessation of breathing and/or blood supply to the brain.

      When the number of birds to be killed is small, and other methods of killing are not available, conscious birds of less than 3 kilograms may be killed using cervical dislocation in such a way that the blood vessels of the neck are severed and death is instantaneous.

    2. Requirements for effective use

      i)
      Killing should be performed either by manually or mechanically stretching the neck to sever the spinal cord with consequent major damage to the spinal cord.

      ii)
      Consistent results require strength and skill so team members should be rested regularly to ensure consistently reliable results.

      iii)
      Birds should be monitored continuously until death to ensure the absence of brain stem reflexes.

    3. Advantages

      i)
      It is a non-invasive killing method.

      ii)
      It can be performed manually on small birds.

    4. Disadvantages

      i)
      Operator fatigue.

      ii)
      The method is more difficult in larger birds.

      iii)
      Requires trained personnel to perform humanely.

      iv)
      Human health and safety concerns due to handling of the birds.

      v)
      Additional stress to the animals from handling.

  2. Decapitation

    1. Introduction

      Decapitation results in death by cerebral ischaemia using a guillotine or knife.

    2. Requirements for effective use

      The required equipment should be kept in good working order.

    3. Advantages

      The technique is effective and does not require monitoring.

    4. Disadvantages

      i)
      The working area is contaminated with body fluids, which increases biosecurity risks.

      ii)
      Pain if consciousness is not lost immediately.


Article 7.6.18.


Pithing and bleeding

  1. Pithing

    1. Introduction

      Pithing is a method of killinganimals which have been stunned by a penetrating captive bolt, without immediate death. Pithing results in the physical destruction of the brain and upper regions of the spinal cord, through the insertion of a rod or cane through the bolt hole.

    2. Requirements for effective use

      i)
      Pithing cane or rod is required.

      ii)
      An access to the head of the animal and to the brain through the skull is required.

      iii)
      Animals should be monitored continuously until death to ensure the absence of brain stem reflexes.

    3. Advantages

      The technique is effective in producing immediate death.

    4. Disadvantages

      i)
      A delayed and/or ineffective pithing due to convulsions may occur.

      ii)
      The working area is contaminated with body fluids, which increases biosecurity risks.

  2. Bleeding

    1. Introduction

      Bleeding is a method of killinganimals through the severance of the major blood vessels in the neck or chest that results in a rapid fall in blood pressure, leading to cerebral ischaemia and death.

    2. Requirements for effective use

      i)
      A sharp knife is required.

      ii)
      An access to the neck or chest of the animal is required.

      iii)
      Animals should be monitored continuously until death to ensure the absence of brain stem reflexes.

    3. Advantages

      The technique is effective in producing death after an effective stunning method which does not permit pithing.

    4. Disadvantages

      i)
      A delayed and/or ineffective bleeding due to convulsions may occur.

      ii)
      The working area is contaminated with body fluids, which increases biosecurity risks.


  1. The only preclusion against the use of this method for neonates is the design of the stunning tongs that may not facilitate their application across such a small-sized head/body.

2013 ©OIE - Terrestrial Animal Health Code

Contents | Index Chapter 7.6. Chapter 7.6.