Chickens in the meat industry are sometimes required to be euthanased on-farm if they are weak, sick, injured or unable to walk and will not recover with treatment.
As with all euthanasia of animals, it is important that the method used is humane, meaning the method chosen either kills the animal immediately or renders them insensible until death without causing pain, suffering or distress. For sick and injured animals, it is important that they are killed without delay, to prevent further stress or suffering.
What is cervical dislocation?
Currently, the main method of on-farm euthanasia for meat chickens is ‘cervical dislocation’, where the bird’s neck is quickly stretched to dislocate the first cervical vertebrae from the skull, which then severs the spinal cord and carotid arteries. When carried out by a trained and competent person, this method results in death by stopping the flow of blood to the brain [1].
The scientific evidence indicates that cervical dislocation does not cause immediate insensibility (loss of consciousness) in birds, therefore there may be a short period of time when birds experience pain prior to death. In large birds, the correct technique of cervical dislocation is very difficult to achieve making it an ineffective method of euthanasia for large birds. For this reason, cervical dislocation should only be used for birds <3kgs [1].
What are some alternative methods?
Two potential alternatives to cervical dislocation are non-penetrating captive-bolt or gas killing.
Non-penetrating captive bolt devices have been specifically developed for birds. These devices, when applied correctly, cause irreversible brain damage resulting in immediate insensibility followed by death [2, 3].
Carbon dioxide is commonly used for gas killing of poultry at abattoirs as well as on-farm. High concentrations of carbon dioxide gas have been shown to be aversive (unpleasant) to poultry. Therefore, gas killing should be done using at least a two-phase method whereby non-aversive carbon dioxide concentrations are used until birds have lost consciousness and followed by high concentrations to ensure death [1].
Non-penetrating captive bolt and gas killing offer more humane options for on-farm euthanasia especially in larger birds where cervical dislocation is ineffective. Current barriers to the adoption of alternative on-farm euthanasia methods include access to the technology, portability, concerns about worker health and safety, and training required on farm. These barriers must be urgently overcome to ensure poultry euthanasia is carried out according to current best practice.
References
[1] EFSA (2019) Scientific opinion: killing for purposes other than slaughter – poultry. EFSA Journal 17(11):5850.
[2] HSA (2017) Killing poultry: mechanical methods – non-penetrative captive-bolt.
[3] Bandara RMAS, Torrey S, Turner P et al (2019) Anatomical pathology, behavioural, and physiological responses induced by application of non-penetrating captive bolt devices in layer chickens. Frontiers in Veterinary Science 6:89.
