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  4. What is low atmospheric pressure stunning (LAPS)?

What is low atmospheric pressure stunning (LAPS)?

Low Atmospheric Pressure Stunning (LAPS) is a form of stunning (inducing unconsciousness prior to slaughter) which may offer significant welfare improvements over the main commercial methods of gas and electrical stunning currently used for poultry. Its use in Australia should be considered.

How does LAPS work?

In a LAPS system, birds in their transport containers are placed in a sealed chamber, and the atmospheric pressure is gradually reduced using controlled slow decompression with a vacuum pump. This results in the gradual removal of oxygen in the air thereby causing unconsciousness and death by hypoxia (lack of oxygen) [1].

What are the potential welfare concerns of LAPS?

There is some concern that in LAPS systems, if the decompression rate occurs rapidly, there is a risk of gas expanding within body cavities and becoming trapped, which causes pain and distress in birds. However, in LAPS systems, when decompression occurs at rate at which the body cavities can adjust (i.e. no air is trapped within the body cavities), this risk is avoided. Birds’ respiratory system anatomy also differs from mammals making it unlikely that gas could become trapped in the abdomen during LAPS [2].

What are the potential benefits of LAPS?

Research suggests that, during LAPS, birds display similar behaviours to that observed during gas stunning, including non-aversive gas methods such as nitrogen or argon gas [3]. A report by the European Food Safety Authority concluded that LAPS is acceptable for commercial slaughter of meat chickens weighing less than 4 kg [1].

Potential benefits of LAPS for bird welfare include:

  • Consistency – all birds are exposed to the same pressure at the same time and the pressure does not need to be adjusted according to number, size or density of birds. This is a benefit in comparison to both gas stunning and electric stunning methods which do not provide consistent or uniform stunning.
  • No live bird handling and shackling of birds – in electrical stunning systems, shackling of live birds prior to stunning causes stress and injuries in birds.
  • No aversive gases – the use of high concentrations of carbon dioxide gas has been shown to be aversive and cause distress in birds.
  • Reduced stress – the birds are able to be placed into the LAPS system in their transport containers in darkness which helps keep birds calm.

Can LAPS be used for animals other than poultry?

The current research available on hypoxia and the use of LAPS for poultry, rats and piglets suggests that it could be a commercially viable stunning method for pigs [4]. In Australia, pigs for commercial slaughter are stunned using either electrical stunning or carbon dioxide stunning systems. The use of LAPS could significantly improve animal welfare for pigs at stunning. Similar to the animal welfare benefits it provides birds, in pigs it could reduce stress, allow for group handling, remove the need for aversive gases and provide an irreversible, non-recoverable stun. For this reason, further research and investment should be directed towards the use of LAPS for pig slaughter.


[1] EFSA Panel on Animal Health and Welfare (2017) Scientific opinion: low atmospheric pressure system for stunning broiler chickens. EFSA Journal 15(12):5056.

[2] Vizzier-Thaxton Y, Christensen K, Schilling M et al (2010) A new humane method of stunning broilers using low atmospheric pressure. Journal of Applied Poultry Research 19:341-348.

[3] Mackie N, McKeegan D (2016) Behavioural responses of broiler chickens during low atmospheric pressure stunning. Applied Animal Behaviour Science 173:90-98.

[4] Bouwsema JA and Lines JA (2019) Could low atmospheric pressure stunning (LAPS) be suitable for pig slaughter? A review of available information. Animal Welfare 28:421-432.

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Updated on February 10, 2020
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