In Europe, the welfare of animals, including poultry, at the time of killing is protected by Regulation (EC) 1099/2009. This regulation requires the use of approved stunning methods for poultry in the European Union (EU) and extends to slaughterhouses in third countries exporting meat to the EU.
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Electric water bath system
In this method of killing, conscious birds are hung by their feet upside down on a line of moving metal shackles, and their heads are passed through electrified water before their throats are slit (Hindle et al., 2010).
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Gas stunning
This works by exposing broilers to either a mixture of inert gases (nitrogen and argon) or concentrations of carbon dioxide (CO2), causing a reduction in available oxygen (O2), thus inducing unconsciousness in the birds.
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Stunning at low atmospheric pressure
It kills birds with a slow, continuous and controlled decompression, causing a gradual reduction in oxygen tension in the chamber, leading to progressive hypoxia.
Details of how broiler chickens are killed in the EU
Electric water bath system
80% of broilers in the EU are killed in an electric water bath system (Berg and Raj, 2015). Waterbath stunning was developed to allow quick processing of birds. However, there are several welfare issues associated with this stunning system.
Birds’ feet are compressed during shackling, causing pain (Gentle & Tilston, 2000), especially in birds with thicker feet or suffering from painful lameness due to foot disorders, bone dislocations or fractures. Inverting birds increases the stress levels that poultry are subjected to during the shackling process. Electrical shocks can occur prior to stunning if the bird’s wings contact the water bath prior to head entry (Raj, 1998; Berg & Raj, 2015; Shields & Raj, 2010). Electrical stunning has not been shown to be completely effective. Occasionally, some birds are not properly stunned because they avoid the stunning effect by raising their heads and missing the water (Raj & Tserveni-Gousi, 2000), or their heads enter the water bath but the currents are too low to induce unconsciousness (Hindle et al., 2010, Devos et al., 2018).
Controlled atmosphere or gas stunning
It has become increasingly common in the last 20 years in Northern Europe, mainly due to animal welfare and product quality advantages over water-bath stunning (Berg and Raj, 2015).
It works by exposing broilers either to a mixture of inert gases (nitrogen and argon) or to concentrations of carbon dioxide (CO2), causing a reduction in available oxygen (O2), thereby inducing loss of consciousness in the birds. Compared to electric water bath stunning, a major advantage of controlled-atmosphere stunning is that the locking and shackling of live poultry can be completely eliminated, thus avoiding the fear, anxiety, distress, suffering, distress and pain induced by handling prior to killing (Shields & Raj, 2010).
However, carbon dioxide is an acid gas, causing birds to experience some discomfort and distress before unconsciousness if inhaled at high concentrations (Raj, 1998). In multi-phased stunning systems, birds are first exposed to relatively low concentrations of CO2 (<40%) to be less aversive, and then, once birds are unconscious, they are exposed to a higher concentration (80%-90%), which is sufficient to induce a deeper state of unconsciousness or death (Berg & Raj, 2015; Gerritzen et al., 2013).
Low Atmospheric Pressure Stunning (LAPS)
It is a recently approved method of killing poultry in accordance with EU legislation. It kills birds with a slow, continuous and controlled decompression, causing a gradual reduction in oxygen tension in the chamber, leading to progressive hypoxia (EFSA Panel on Animal Health and Welfare et al., 2017; McKeegan et al., 2013). Loss of posture, considered a behavioural cue for loss of consciousness, occurs on average every 80 seconds (Mackie, N. & McKeegan, 2016).
The major welfare benefits of low atmospheric pressure stunning over electric waterbath stunning systems include no handling of live birds and no shackling (as the birds are nested in the modules used to transport them), no risk of pre-shock and no risk of inefficient stunning as low atmospheric pressure stunning reliably and irreversibly stuns all birds (Mackie, N. & McKeegan, 2016).
Some researchers consider low atmospheric pressure stunning to be superior to controlled atmospheric stunning because low atmospheric pressure stunning does not use any gas during the stunning process and is considered a safer method for both humans in the area and less aversive to the animals. There is also the potential for small slaughterhouses to adapt to this system more easily than controlled atmosphere stunning (Vizzier-Thaxton et al., 2010).
Surse
- Berg, C., & Raj, M. (2015). A review of different stunning methods for poultry—Animal welfare aspects (stunning methods for poultry). Animals, 5(4), 1207-1219.
- Devos, G., Moons, C. P. H., & Houf, K. (2018). Diversity, not uniformity: slaughter and electrical waterbath stunning procedures in Belgian slaughterhouses. Poultry science, 97(9), 3369-3379.
- EFSA Panel on Animal Health and Welfare (AHAW), More, S., Bicout, D., Bøtner, A., Butterworth, A., Calistri, P., … & Michel, V. (2017). Low atmospheric pressure system for stunning broiler chickens. EFSA Journal, 15(12), e05056.
- Gentle, M. J., & Tilston, V. L. (2000). Nociceptors in the legs of poultry: implications for potential pain in pre-slaughter shackling. ANIMAL WELFARE-POTTERS BAR-, 9(3), 227-236.
- Gerritzen, M. A., Reimert, H. G. M., Hindle, V. A., Verhoeven, M. T. W., & Veerkamp, W. B. (2013). Multistage carbon dioxide gas stunning of broilers. Poultry Science, 92(1), 41-50.
- Hindle, V. A., Lambooij, E., Reimert, H. G. M., Workel, L. D., & Gerritzen, M. A. (2010). Animal welfare concerns during the use of the water bath for stunning broilers, hens, and ducks. Poultry science, 89(3), 401-412.
- Mackie, N., & McKeegan, D. E. (2016). Behavioural responses of broiler chickens during low atmospheric pressure stunning. Applied Animal Behaviour Science, 174, 90-98.
- McKeegan, D. E. F., Sandercock, D. A., & Gerritzen, M. A. (2013). Physiological responses to low atmospheric pressure stunning and the implications for welfare. Poultry Science, 92(4), 858-868.
- Raj, M. (1998). Welfare during stunning and slaughter of poultry. Poultry science, 77(12), 1815-1819.
- Raj, M., & Tserveni-Gousi, A. (2000). Stunning methods for poultry. World’s Poultry Science Journal, 56(4), 291-304.
- Shields, S. J., & Raj, A. B. M. (2010). A critical review of electrical water-bath stun systems for poultry slaughter and recent developments in alternative technologies. Journal of Applied Animal Welfare Science, 13(4), 281-299.
- Vizzier-Thaxton, Y., Christensen, K. D., Schilling, M. W., Buhr, R. J., & Thaxton, J. P. (2010). A new humane method of stunning broilers using low atmospheric pressure. Journal of Applied Poultry Research, 19(4), 341-348.
- The information from this article have been compiled by the Open Wing Alliance