Defra - Department for Environment, Food and Rural Affairs.

Science Search

Science and Research Projects

Return to Science Search homepage   Return to Project List

Developing an alternative method to the use of high concentration CO2 for the commercial stunning of pigs - MH0154

Pigs are commonly rendered unconscious (stunned) with carbon dioxide gas before slaughter, but this practice gives rise to important welfare concerns because it induces breathlessness and above certain concentrations, pain. Induction of unconsciousness by hypoxia (lack of oxygen) is considered to be more humane, and experiments indicate that pigs do not find it aversive. However, achieving this sort of stun with inert gases such as argon and nitrogen is technically problematic and is considered to be too expensive for commercial use. Low Atmospheric Pressure Stunning (LAPS) is a possible alternative, whereby animals are rendered unconscious by gradually reducing air pressure and therefore oxygen availability to achieve a progressive hypoxia. This is called hypobaric hypoxia and is equivalent to rapidly ascending to high altitude, which is reported as not unpleasant or painful to humans. LAPS has been developed for commercial use to stun poultry and it has been shown to be as humane as immersion in inert gases. The aim of this project is to systematically investigate the feasibility of developing LAPS as a humane, reliable and efficient method of stunning for commercial pigs. Initially, we will conduct experiments to determine suitable and effective decompression rates for pigs, aiming to achieve a commercially feasible cycle time, while attempting to minimise welfare compromise. If effective curves are identified, extensive behavioural and physiological welfare assessments during LAPS will then be carried out. We will determine the time to loss of consciousness during LAPS and specifically look for signs of pain, anxiety and aversion to the process. The responses of pigs undergoing LAPS will be compared to pigs exposed to carbon dioxide in the same way as current commercial practice, to evaluate if LAPS is demonstrably more humane. Pathological assessments will also be conducted to check for signs of organ damage. For LAPS to be an economically feasible alternative to current practice there should be no compromise to meat quality and little impact on current slaughter line productivity (i.e. throughput rates). Therefore meat quality parameters will be measured and an economic feasibility analysis conducted to assess commercial viability. Encouragingly, the nature of LAPS systems would allow group stunning and minimal stressful handling similar to that currently used. It may be that LAPS is not a suitable method for the stunning of pigs, either because it is associated with unexpected and/or unavoidable welfare costs or because it cannot be achieved humanely in a cycle time that is suitable for application to commercial slaughter – in anticipation of this, we have built into our project key decision points where our steering group, including stakeholders and funders, will carefully consider if the work should continue.
1.Assessments the effectiveness of the proposed method for stunning adult pigs using defined parameters and including an assessment of practical viability, installation and operating costs, physical damage to carcasses and effects on meat quality.
2.Measurements of time to loss of consciousness, duration of loss of consciousness and the time between loss of consciousness and death.
3.Behavioural, physiological and neurological assessments of any suffering and distress prior to loss of consciousness. This shall include an assessment of aversion to the proposed method.
4.A commercial feasibility and economic cost-benefit analysis of the proposed method.
Time-Scale and Cost
From: 2018

To: 2020

Cost: £307,923
Contractor / Funded Organisations
University of Glasgow
Fields of Study
Animal Welfare