Back in Sight, Back in Mind: AWI Petitions to Require Cameras to Monitor Pigs Slaughtered with CO2 Gas

Out of sight, out of mind. The adage captures one of AWI’s central concerns when it comes to the slaughter of pigs in the United States. Most are stunned or killed in the steel-walled confines of carbon dioxide (CO2) gas chambers, out of view of federal inspectors. Consequently, those inspectors have no way of assessing the humaneness of the slaughter process or reporting stunning-related humane violations. To address this problem, AWI submitted a rulemaking petition that requests mandatory video cameras inside the gondolas (steel cages or compartments) that are used to convey pigs into the gas chambers. The cameras would be required to both record and provide live footage of the pigs while they are being gassed. This would, for the first time, enable inspectors to evaluate the humaneness of CO2 use during the slaughter of pigs and to intervene when welfare violations occur.

photo by Raven Deerbrook
photo by Raven Deerbrook

Use of CO2 slaughter in the United States
In a typical slaughter plant, small groups of pigs are loaded into a gondola, which is then lowered into a chamber filled with CO2. The gas eventually causes loss of consciousness, or death if exposure is long enough. Stunning can take a minute or more; killing can require several minutes. After stunning, the animals are dumped out of the gondola, strung up head down, bled, and butchered.

CO2 gas has been used in the slaughter of pigs in the United States for decades. Over the last 20 years, however, its popularity within the pork industry has skyrocketed. In 1999, CO2 was used to stun about 2 percent of pigs at slaughter. By 2020, it was used to stun about 86 percent of all pigs and 96 percent of pigs in the largest slaughter plants. That year, more than 110 million pigs were stunned or killed using CO2—several times the total combined number of slaughtered cattle, calves, and sheep (about 36 million). Today, according to AWI’s review of US Department of Agriculture enforcement records, at least 32 slaughter plants use CO2 gas systems to stun or kill pigs. 

A long list of welfare concerns 
Enabling inspectors to observe CO2 use in slaughter is critically important, because many pigs suffer from the effects of the gas. They can experience respiratory distress, hyperventilation, a sense of breathlessness, gasping, suffocation, convulsions, fear, panic, stress, and pain from irritation of the eyes and mucous membranes that line the throat and nose. These effects were revealed to the public for the first time in videos taken by an undercover investigator in October at a Smithfield Foods meatpacking plant in Los Angeles. As described in a Wired magazine article published in January, the recordings showed that, as the gondola was lowered into the gas pit, “the pigs began to squeal and thrash violently around in the cage, struggling to escape and convulsing for nearly a minute before finally laying still.” As the investigator told Wired, “Pigs are very human-like in their screaming. And I wasn’t expecting to see them suffer for so long. … I knew it was going to be bad. But I wasn’t really prepared for the screaming.” 

Indeed, exposure to the high concentrations of CO2 gas typically used by slaughter plants can cause pigs so much pain and fear that the European Food Safety Authority has called for replacing it with other gas mixtures (such as nitrogen and argon) that are less aversive—calls that have so far gone unheeded by the pork industry in the United States.

Making matters more complex—and adding urgency to the need for careful monitoring—is the fact that not all pigs suffer in the same ways or for the same reasons. The severity of distress and discomfort caused by CO2 and length of time it takes the gas to render pigs unconscious can vary widely among individual pigs and groups of pigs due to a panoply of factors. For example, individual pigs and different breeds or ages of pigs may react differently when exposed to the same quantity and concentrations of gas, with some showing little or no struggling, while others exhibit elevated levels of distress through crawling, attempting to escape, and piercing screams.

If the temperature or humidity of the gas falls too low, it can cause burns on the skin or pain during inhalation. Loud sounds, such as from machinery and the screams of other pigs in the stunner, can compound stress experienced during CO2 exposure. Rough handling of pigs as they are moved toward the stunning area also increases the likelihood of an aversive reaction to CO2. This is recognized in the USDA’s own humane slaughter regulations: “Delivery of calm animals to the [CO2 gas] anesthesia chamber is essential since the induction, or early phase, of anesthesia is less violent with docile animals.” 

Further, research has found that sex, age, health conditions, breed, and genetics can all affect how rapidly pigs lose consciousness upon exposure to CO2. Overloading of gondolas can also play a role: When overcrowded animals fall on top of each other, it can compress their chests and lead to insufficient inhalation of gas. Yet another factor is the speed at which the gondola descends into the pit. Faster conveyor speeds could reduce the time of exposure to the gas, which could result in animals that are not rendered as deeply unconscious, or unconscious at all.

Even outdoor environmental conditions such as wind, temperature, and humidity can affect pigs by reducing the CO2 concentration in the gas chamber when doors are opened and closed or fans are turned on and off within the plant. Lower gas concentrations typically prolong the time to unconsciousness and may result in a shallower plane of anesthesia, increasing the risk that pigs will regain consciousness while they are being hoisted by a back leg and cut for bleeding. 

The urgent need for observation
It is evident that a worrisome host of variables could cause any individual pig or group of pigs loaded into a CO2 gondola to experience severe suffering. That is why it is urgently important that federal inspectors be able to directly observe the stunning or killing as it is taking place. This would enable them to assess, each time a gondola is lowered into the gas chamber, the extent to which any individual pig or group of pigs is suffering and whether any violations of federal humane requirements are occurring—and if so, suspend slaughter operations until corrections are made.

Yet, inexplicably, the use of CO2 remains the only approved method of slaughter that occurs out of inspectors’ view. In contrast, captive bolt stunners, electrical stunners, and firearms are used in areas where inspectors can actually watch and hear the process. This lack of visual access when CO2 is in use is particularly egregious given that the vast majority of pigs are slaughtered with CO2. It is also unlawful: The Federal Meat Inspection Act and Humane Methods of Slaughter Act require inspectors to conduct an “examination and inspection” of all methods of stunning and killing at slaughter and to assess whether those methods are humane. If inspectors are unable to observe the use of CO2 to stun or kill pigs, there is no way they can examine or inspect the slaughter process, or determine if it is humane.

To address this logical and legal shortcoming, AWI and its allies petitioned the USDA’s Food Safety Inspection Service to amend its regulations to require that (1) cameras be installed inside all gondolas used in CO2 gas systems and (2) the cameras both record and provide live video (including audio) of the entire interior of the cage and all of the animals inside during the gassing operation. No animals could be loaded into a gondola unless these standards are met.

Installing cameras in gondolas would not be a significant burden for the many slaughter plants that already use cameras in other areas of their facilities. On the contrary, it would benefit their operations by helping to alert them to problems that may need to be addressed—such as improper gas concentrations, temperature, or humidity; overloading of the gondola; or improper gondola speeds—any of which could influence how rapidly and effectively pigs are stunned and killed. It would also align with the advice of researchers such as renowned animal behaviorist Dr. Temple Grandin, who has long called for the use of video cameras to observe pigs while they are being stunned or killed with CO2 gas. 

So long as the stunning and killing of pigs with CO2 continues to occur out of sight, with no opportunity to observe what is happening on the other side, plant inspectors will remain unable to evaluate whether slaughter is occurring humanely, as the law requires. Mandating the placement of cameras inside gondolas used in CO2 systems would be a simple, affordable, and effective step toward bringing the welfare of pigs back into view, and back into the minds, of inspectors with the power to enforce what humane regulations require. 

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