The efficacy of three on-farm euthanasia methods for broiler chickens throughout the production cycle

ABSTRACT

1. There is a need to humanely kill moribund or injured broiler birds on-farm with no reasonable chance of recovery. Two experiments evaluated the efficacy of three commercially applicable killing methods; manual cervical dislocation (CD), mechanical cervical dislocation with the Koechner Euthanising Device (KED) and a non-penetrative captive bolt device (Zephyr-EXL; ZEXL), at 7, 21 or 35 d of age, on their ability to induce insensibility (unconsciousness and loss of brain stem reflexes) and death.

2. Experiment one assessed the damage to the cranial-cervical region resulting from the methods applied to cadavers of cull birds (n = 180) by radiography and gross pathology observation.

3. Experiment two evaluated the latency to insensibility and death when cull broiler birds (n = 240) were killed by CD, KED or ZEXL, using behavioural and reflexive indicators. Insensibility and death were measured by the absence of pupillary light, palpebral blink and nictitating membrane reflexes and cessation of rhythmic breathing, cloacal winking and convulsions. Analysis of variance for the main effect of the method was performed to determine the differences.

4. In experiment one, only the Zephyr resulted in skull fractures. A higher number of vertebral fractures occurred with KED application compared to CD, at 21 and 35 d.

5. In experiment two, indicators of sensibility were absent earliest with the ZEXL (μ < 2 s); then,CD (μ = 28 s) and were longest with KED (μ = 47 s), at 21 and 35 d. Cloacal winking and convulsions ceased earlier after CD (88 s), compared to either KED (124 s) or Zephyr (118 s). Death after a single application occurred 100%, 100% and 98% of time for CD, KED and ZEXL, respectively.

6. Overall, all methods were efficacious at inducing insensibility and death. Insensibility occurred earliest with ZEXL, whilst death occurred earliest with CD. KED resulted in the longest time to insensibility and death.

KEYWORDS:

• Husbandry
• cervical dislocation
• non-penetrative captive bolt
• brainstem reflexes
• brain death
• cull
• unconsciousness

Acknowledgments

The authors would like to thank the Saskatchewan producers that participated in the study, as well as, Dorien Brosnihan, Chicken Farmers of Saskatchewan, Poultry Industry Council, Canadian Poultry Research Council, Egg Farmers of Canada, Hybrid Turkeys, the Ontario Ministry of Agriculture, Food and Rural Affairs, and Natural Sciences and Engineering Research Council for funding this study. None of the funders were involved in study design, data collection, analysis or interpretation, writing or submitting of the manuscript. The authors wish to thank veterinary pathologist Dr. P.V. Turner at the University of Guelph for post mortem haemorrhage examination of the cadavers.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Canadian Poultry Research Council [417630]; Natural Sciences and Engineering Research Council of Canada [CRDPJ482074 2015]; Chicken Farmers of Saskatchewan [417370]; Poultry Industry Council [052509].