Scientists warn that millions of pigs suffer agonising deaths in the UK every year
Research commissioned by Animal Equality and published in a leading peer-reviewed academic journal raises alarm bells over the stunning of pigs using CO2 gas at slaughter.
New academic research, published this month in Frontiers in Veterinary Science, raises serious concerns over the use of CO2 gas to stun pigs at slaughter. The journal, ranked in the top quartile for veterinary science by SCImago Journal Rank, highlights the growing alarm within the scientific community about this controversial method.
The research – co-authored by Jenny Mace and Veterinary Professor Andrew Knight of the University of Winchester, and commissioned by Animal Equality UK – argues that stunning pigs with high concentrations of CO2 causes pain, fear, and respiratory distress in their final moments.
Each month, nearly one million pigs are slaughtered in the UK for human consumption. In England and Wales, 88% of pigs are reportedly stunned and killed using this method, which has been condemned by the Animal Welfare Committee (AWC) for over two decades. Despite the evidence, its use remains legally permissible.
How are pigs killed with CO2?
Pigs are forced into gas chambers, which are often designed like a paternoster system. In this setup, groups of pigs enter a cage that descends into a pit filled with CO2, which is heavier than air and remains trapped at the bottom. The lifeless bodies are then raised on the other side as the cycle continues – an underground Ferris wheel of death. These cages are even referred to as ‘gondolas’.
As the pigs inhale CO2, the gas irritates the pigs’ throats and nostrils, and causes acid to form on their eyes. It creates a sense of breathlessness, hyperventilation, and ‘air hunger’. For an average of three to five minutes, pigs endure agony before they eventually die. During some of this time, pigs can be seen gasping, squealing, and attempting to escape – clear signs of pain and distress. Abigail Penny, the Executive Director of Animal Equality UK, argues that CO2 gassing of pigs is “indisputably among the most grave welfare abuses of our time, causing unimaginable and indefensible agony to millions of vulnerable animals every year”.
What can be done?
In their study, the experts compare alternative stunning methods such as inert gases, electrical and mechanical methods, low atmospheric pressure stunning, and nitrogen foam. In particular, they consider the use of argon which they describe as the ‘least aversive alternative’ given that pigs lose consciousness more quickly, and since gas chambers in existing slaughterhouses could be adapted for this use.
However, they warn that argon must be treated merely as ‘a much needed stopgap until a less aversive solution is found’. They warn that gassing pigs with argon would still be a ‘far from an ideal alternative’ – since pigs still show signs of gasping and air hunger. With this in mind, they recommend urgent research on the topic.
Although stunning using argon gas is still not acceptable from animal welfare or ethical perspectives, it is certainly more humane than CO2 gassing. Current abattoir gassing systems using CO2 should be modified without delay to systems that use argon gas. We owe it to the many millions of pigs who are slaughtered for food each year”.
– Veterinary Professor Andrew Knight, University of Winchester
There have been calls to phase out the CO2 gassing of pigs for decades. The extremely slow movement on this is hugely regrettable and concerning. We must use the renewed current momentum to finally secure a shift to more humane methods of pig stunning and slaughter that are at the industry’s disposal.
– Jenny Mace, University of Winchester
A kinder way?
Every single minute, millions of pigs are enduring excruciatingly painful deaths, all for human consumption. The reality is there is no humane way to kill an animal who doesn’t want to die, and the kindest course of action is to choose plant-based and leave animals off of your plate.
In the meantime, for those animals trapped in the cruel pig industry, the extreme suffering caused by high intensity CO2 gassing must be immediately phased out. Our team is calling on Government Ministers to take immediate action. We’ve already submitted the findings of this study through a private consultation with the Animal Welfare Committee, a key Government advisory body.
The UK Government pledged to ‘deliver the most significant boost in animal welfare in a generation’, and with the overwhelming scientific evidence now on the table we must ensure they uphold that promise. We will continue to demand accountability and do everything in our power to end the use of CO2 gassing.
The most powerful action that you can take as a consumer is to switch to plant-based alternatives today. Share the truth about how pigs are slaughtered with your family and friends – help them understand the reality so they too can be inspired to act. Together, we can bring about the change that animals truly deserve.
protect pigs
Pigs are highly social animals who are often considered smarter than dogs. You can protect these intelligent animals by simply choosing plant-based alternatives.
