CO2 is an expiratory gas and animals have evolved an appropriate response to high levels. Upon exposure animals experience what can be called a panic attack, with rapid breathing, claustrophobia and high levels of stress. In fact researchers believe that people who suffer from panic attacks might have a hypersensitive mechanism. The solution therefore might be considered rather simple. If animals have an evolved response to CO2, why not use a different gas, or even no gas at all; why not simply remove the air?
The use of the inert gasses argon and nitrogen are often touted as alternatives, but tests using pure forms of the gases to kill mice resulted in drawn out and unpleasant deaths. Attempts to anaesthetize mice with gasses such as isoflurane prior to the CO2, also did not give improved welfare results.
Low Atmospheric Pressure Stunning - LAPS
In the LAPS system birds are placed in a sealed container and the air is slowly removed. The result is said to be painless and controlled. Comparisons are made to aircraft pilots who gradually lose consciousness in high altitudes but do not experience averse reactions. In comparison to electric stunning, LAPS is comparable to CO2 stunning in that there is no handling of the animals and the birds are stunned while in their transport containers (cages) to reduce stress. After initial concerns that there was not enough evidence that this novel method of slaughter was humane, an additional welfare study on LAPS carried out by the University of Glasgow for the European Union, found LAPS to be of a higher standard of welfare than electric stunning and at least as humane as the controlled atmosphere killing. It was therefore passed for use in the slaughter of poultry in the UK as of May 2018 as early as 2013 in Canada and 2010 in the USA.
A major criticism of LAPS is the lack of research in this novel method. Previous attempts to legalize LAPS in the UK failed due to a lack of research. LAPS was declined for legalization as recently as 2017. The 2018 decision to legalize LAPS was based on the result of the single study carried out by the University of Glasgow on 90 broiler chickens. The experiment monitored the electrical activity of the brain (EEG) and heart (ECG) and analysed the chickens’ behaviour through an infrared camera. The paper claims no signs of averse behaviour were detected. What though counts as averse behaviour? In a scientific setting, it is possible to detail some well defined parameters and then to say that the behaviour of the animals did not fall within them. Such was the criticism of an article (dated 2011) by the United Poultry Concern (UPC) of the United States.
‘At this stage, flapping of the wings began by some birds accompanied by a low, guttural moaning in all treatments, except Treatment 3. It should be noted that the moaning was not considered a vocalization for purposes of determining the subjective slaughter score.’
The article however does exagerate the effects of LAPS, at least as far as its use in the EU. There was no evidence of barotrauma to the ears for instance. It is possible, but unknown if decompression could cause pain to the birds sensitive ears.
Because of the difficulty in killing an animal without suffering, it is desired that they are rendered unconscious first; hence the term ‘stunning’. The problem therefore exists in determining at what point an animal is rendered unconscious. Scientist studying the welfare of animals often use an EEG (electroencephalogram) to determine the point at which an animal is unconscious. Similarly an ECG (electrocardiogram) is used to judge the level of pain. Neither is an exact science and further research is needed.
‘Although often descriptive, the use of EEG as an objective measure of unconsciousness, or determination of state of consciousness, especially for decision-making related to the humaneness of euthanasia methods, is an area of research that requires further exploration.’
‘Other studies have examined the use of heart rate variability as a marker of pain. A recent review concluded that no validated objective markers of nociception or pain recommended for clinical use in humans are available currently, although the authors noted that the analysis of heart rate variability potentially could be developed for this purpose. Certainly additional studies in this area are required to evaluate the benefits of heart rate variability as a tool for assessment of pain and distress.’
They do however remain the best current option.
All animal slaughter methods are either painful or cause distress. Selecting the best one is currently a matter of selecting the least painful and distressing. The European Union maintains some of the highest standards in the world but the lack of research in the introduction of new methods is cause for alarm.