Is humane slaughter possible? How pigs are really killed

The objection

“I don’t support cruelty, I support humane slaughter. The animal feels nothing and dies quickly. So what’s the problem?”

The answer

The objection rests on a death that the most common methods don’t deliver. In England and Wales 90% of pigs are stunned with high-concentration carbon dioxide (FSA, 2024) [1], which the scientists advising the UK government and the EU on animal welfare find causes pain, fear and respiratory distress before the pigs lose consciousness [2][3].

Suppose the death were genuinely painless. The pig would still be killed, and we don’t accept gently killing an unwilling person, because the wrong lies in taking a life that had its own interest in continuing. Nor is the death necessary: the British Dietetic Association says carefully planned plant-based diets “can support healthy living at every age and life stage” [4], and the US Academy of Nutrition and Dietetics’ 2025 position is that appropriately planned vegetarian and vegan diets can be nutritionally adequate for adults [5].

How are pigs killed in the UK?

In England and Wales, 90% of pigs were stunned with high-concentration CO₂ in the Food Standards Agency’s survey week in February 2024, up from 88% in 2022, and almost all the rest were stunned electrically, a government figure [1]. The pigs are lowered in cages into a pit of the gas [3] at 8 plants in England, which between them handle 90% of domestic production [1]. Northern Ireland has 3 such plants, Scotland 1 and Wales none [2]. The industry moved to gas from automated electrical stunning because pigs can stay in groups, which the government’s Animal Welfare Committee (2025) says reduces stress for the pigs and for the people running the system, and because it allows faster lines and better meat [2]. The gas also acts faster than inert gases such as argon, and the committee cites an EU research estimate that an argon system would cost two to three times as much per pig [2]. Yet the committee found argon significantly less aversive than CO₂ [2], and Defra’s strategy reports the committee’s conclusion that argon and automated electrical stunning are higher-welfare alternatives, which the strategy calls commercially feasible [7].

What does CO₂ stunning do to a pig?

Breathing high-concentration CO₂ causes pain, breathlessness and fear before the pig loses consciousness, the UK government’s Animal Welfare Committee concluded in 2025 [2]. The gas dissolves in the moist membranes of the eyes, nose, mouth and lungs to form carbonic acid, and commercial concentrations far exceed the level of around 40 to 50% at which it starts to trigger pain receptors [2]. It also brings on “air hunger”, the urge to breathe that in people comes with anxiety and panic, and the committee expects pigs to feel the same; breathing harder brings no relief, because every deeper breath draws in more gas [2]. Pigs vocalise, hyperventilate and try to escape before they collapse, and in the studies the committee reviewed they took 21 to 60 seconds to lose consciousness [2]. The European Food Safety Authority (2020) called the gas “highly aversive” and found the pain, fear and respiratory distress it causes “inherent to the stunning method”, with no way to prevent them except using other gas mixtures [3].

Is the UK going to ban CO₂ stunning?

The UK government has said it will consult on banning CO₂ stunning of pigs in England, but as of October 2026 the consultation had not opened [8]. Its advisers have wanted the method gone for more than twenty years. In 2003, when about a third of pigs killed in Great Britain were gassed, the Farm Animal Welfare Council called high concentrations of CO₂ “not acceptable” and asked for them to be phased out within five years [6], yet by 2024 the share in England and Wales was 90% [1]. In 2025 the council’s successor, the Animal Welfare Committee, concluded that the gas “should be prohibited” for pigs [2], and that December the government’s animal welfare strategy for England said it wants “to see an end to the use of CO2 gas stunning” and committed to a ban, subject to a consultation [7]. On 22 October 2026, answering for Defra in Parliament, Stephen Morgan said only that the government “will consult” on a ban and on possible timescales for phasing the method out, with “further details” to come “soon” [8].

How are pigs killed in Ireland, Australia, the US, Canada and New Zealand?

In Ireland, Australia and the US most pigs are gassed, in Canada the food inspection agency says the gas systems used in North America expose pigs to high concentrations of CO₂ but gives no share, and in New Zealand the rules don’t allow the gas for pigs. In June 2026 Ireland’s agriculture minister told the Dáil that “the majority of pigs are stunned by carbon dioxide in high concentration”, as EU rules allow at a minimum of 80% [9][11]. Asked how many, the minister gave no figure, and in a second answer said no specific review of how Irish pigs are stunned has been carried out [9][10].

Australia’s pig industry body, Australian Pork Limited, estimates that about 85% of the country’s pigs are processed at seven export abattoirs, all of which use CO₂, and Victorian government figures put the share gassed in Victoria at about 93% in 2022–23 [12]. The method was caught on film in 2023, when investigators hid cameras at a slaughterhouse near Adelaide and recorded the pig gas chamber there. In an industry-funded study at five Australian abattoirs (2021), between 0.6% and 46% of pigs crawled or tried to escape in the gondola, depending on the abattoir [13][14]. In June 2024 a committee of Victoria’s parliament found the gas “aversive to pigs who experience high levels of pain and stress” [12], and six months later Victoria’s government replied that CO₂ was “currently considered the best practice method” while admitting “no success to date” in developing “a less aversive practical viable alternative” [14], a defence that concedes the gas is aversive.

The US government publishes no figure and turned down the Animal Welfare Institute’s request for one, but Pig Improvement Company data quoted in that group’s 2023 petition put CO₂ stunning at 86% of US pigs in 2020, an industry estimate [15]. Canada’s food inspection agency says some pigs react to the high concentrations used in North America “by attempting to escape and showing marked shaking of their heads” [16]. New Zealand’s slaughter code allows pigs to be stunned only with a captive bolt, an electrical stunner or a firearm [17], which shows the gas is a choice, yet nearly 62% of the pork eaten there from January to September 2024 was imported, according to NZ Pork’s data, an industry figure, with the US the biggest supplier and Australia among the other major ones [18].

Are cattle and chickens killed more humanely?

Not reliably: a badly placed captive bolt can leave a cow conscious, and an NGO estimate found that in 2019 most chickens killed in the US were hung upside down in shackles while conscious. In England and Wales 82% of cattle were stunned with a captive bolt in 2024 [1]. The European Food Safety Authority (2020) counts ineffective stunning as an important welfare concern for cattle, because an animal that is not properly stunned stays conscious through hoisting, sticking and bleeding [19]. Among the studies it reviews, one (2012) found 35% of cattle inaccurately shot in abattoirs with no device to steady the head, and another (2012), of 8,879 skulls from two slaughterhouses, found about 65% shot in the ideal position and direction, 31% with medium precision and 3 to 4% with poor precision, and some skulls with more than one hole [19]. These figures record where the bolt landed and say nothing directly about how many cattle stayed conscious, but EFSA lists a shot in the wrong position or direction among the hazards that can stop an animal losing consciousness or let it recover before or during bleeding [19].

Chickens are killed in far greater numbers: in the same survey week in February 2024, abattoirs in England and Wales killed 18.4 million meat chickens and 161,748 pigs [1]. About 77% of those chickens were gassed and 19% were stunned in electrical water baths used for halal slaughter [1]. In a water bath, conscious birds are hung upside down by their legs in metal shackles on a moving line and their heads pass through electrified water [20]. EFSA’s 2019 opinion on poultry slaughter says that shackling a bird and holding it upside down “causes pain and fear”, and cites a 1997 study in which about 90% of birds flapped their wings immediately after being shackled [21]. In the US, The Humane League Labs estimated that 92% of chickens killed in 2019 were electrically stunned this way, an NGO estimate [20], and the USDA says there is “no specific federal humane handling and slaughter statute for poultry”, though poultry inspection law still requires live birds to be handled in line with “good commercial practices” [22].