Assessing the effect of water deprivation on the efficacy of on-farm euthanasia methods for broiler chickens

ABSTRACT

1. Moribund or diseased poultry requiring euthanasia are often dehydrated. To understand how dehydration influences the efficacy of various killing methods, this experiment investigated the effect of water deprivation (WD) on times to unconsciousness and death.

2. Broiler chickens (n = 179) were water-deprived for 0, 24, 48 or 72 hours to mimic dehydration, then killed via manual cervical dislocation, mechanical cervical dislocation (Koechner Euthanising Device (KED)), or non-penetrating captive bolt (Zephyr-EXL), at 8, 22, 36 or 50 d of age. Degree of WD was confirmed by skin turgor, packed cell volume and body weight loss. Method efficacy was evaluated by the time to unconsciousness and death using pupillary light (PUP), palpebral blink (PAL) and nictitating membrane (NIC) reflexes, feather erection (FE), cloacal winking (CW) and convulsions (CN). The extent of damage caused by each method was examined via radiography, gross pathology and histopathology. The main effects of WD time and euthanasia method were analysed by two-way analyses of variance (CRD, PROC MIXED, SAS 9.4) with a-priori contrasts to compare water-deprived versus non-water-deprived (NON) birds.

3. Skin turgor, packed cell volume and body weight loss had a quadratic relationship with WD, with highest values for those birds which were water-deprived for 72 h. WD level did not affect time to unconsciousness. Time to death was longer for WD birds than NON, with longer latencies to FE, CW and CN for water-deprived birds. WD only affected radiography or gross pathology scores on d 8, with the extent of subcutaneous haemorrhage within the neck decreasing as WD increased.

4. The shortest latency to PUP loss, at all ages, and to PAL and NIC loss, at 22 d, was with the Zephyr-EXL. KED had the longest time to unconsciousness (PUP, PAL and NIC), at all ages, and to death, at 36 and 50 d.

5. Overall, WD increased time to death, but did not affect the onset of unconsciousness, with no interaction between methods and WD level.

KEYWORDS:

• Poultry
• cull
• dehydration
• insensibility
• death

Acknowledgements

The authors would like to thank the 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. Funders were not involved in the study design, data collection, analysis or interpretation, writing or submitting of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Canadian Poultry Research Council [Project PWB079]; Natural Sciences and Engineering Research Council of Canada [CRDPJ 482074 - 2015]; Chicken Farmers of Saskatchewan [UofS417370]; Egg Farmers of Canada [UofS417630]; Poultry Industry Council [PROJ #326].