Abstract
We evaluated three models of non-penetrating captive bolt devices, Zephyr-E, Zephyr- EXL, and Turkey euthanasia device (TED) for time to loss of sensibility and degree of brain damage during euthanasia in four age groups of male and female layer chickens (10–11, 20–21, 30–35, 60–70 weeks respectively). Latencies to onset of insensibility and cardiac arrest were assessed to detect whether killing birds via these devices was humane and effective. Both gross and microscopic pathology evaluations were conducted to score skull and brain trauma post mortem. All three NPCB devices induced loss of breathing, pupillary reflex and nictitating membrane reflex within 5 s after application in most chickens. Latencies to loss of jaw tone and neck muscle tone were longer in 60–70 weeks old roosters (p < 0.05). Younger birds (10–21 week-old) demonstrated the longest time (p < 0.0001) to onset of tonic convulsions, time at last movement, cloacal relaxation and cessation of heart beat. A positive correlation (p < 0.0001) was found for all three devices between time of cardiac arrest and times to onset of tonic convulsions, last movement, and cloacal relaxation. More than 80% of birds had skin lacerations with external bleeding following application of all 3 devices. Device type did not affect the incidence of skull fractures but higher skull fracture scores were noted in 10–11 week-old birds compared to other ages. Regardless of device type and age, microscopic SDH was most apparent in the brain and proximal spinal cord of all birds. In summary, all three devices caused significant trauma to the midbrain and spinal cord. Results demonstrated that all three devices induce rapid insensibility after application and can be used as a single-step method that results in a humane death in all age groups of layer chickens.
Highlights
In the poultry industry, there are several reasons for killing birds during production: to prevent suffering from sickness or injury, for disease control, and for stock management
100% successful killing was observed for the Turkey euthanasia device (TED) with immediate and irreversible insensibility in all age groups
Results of the present study revealed longer time to loss of jaw tone and neck muscle tone for TED compared to the Zephyr devices, which corresponded to differences in parenchymal hemorrhage (PCH) scores in the hind brain between devices
Summary
There are several reasons for killing birds during production: to prevent suffering from sickness or injury, for disease control, and for stock management. Onfarm killing is a routine procedure on commercial poultry farms. Animal care guidelines for livestock and poultry require that the methods used for routine killing cause minimal pain and distress [1]. The killing method should result in rapid and irreversible loss of sensibility (or consciousness) to be considered humane [2]. The most common method for killing poultry on farms is manual cervical dislocation which involves stretching and separating the cervical vertebrae by hand. A NPCB device is commonly used to stun large mammals such as cattle, slaughter weight pigs and adult sheep, but is not recommended as a sole method of euthanasia for large animals, as it may not cause death as a one-step method of euthanasia and another method is not applied animals may return to sensibility [2, 7]
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