Higher Welfare Method for Stunning Pigs Gains Ground

In the United States, federal regulations require that pigs be stunned prior to slaughter by one of four methods: electricity, chemicals (gas), captive bolt device, or gunshot. The smallest slaughter plants generally use gunshot or captive bolt; mid-sized plants often use electricity, and the nation’s largest pork companies—Smithfield Foods, Tyson Foods, and JBS USA—mostly use carbon dioxide (CO2) gas to stun pigs.

Gas stunning provides some animal welfare advantages in that it doesn’t require restraint and allows pigs to be moved in groups, which reduces pre-slaughter handling stress. Both laboratory research and anecdotal evidence from slaughter facilities, however, have shown that CO2 can be aversive to pigs, who take up to 60 seconds to lose consciousness when exposed to the gas.

The use of CO2 is considered a humane and acceptable method of stunning pigs in Australia, in the European Union, and by the World Organization for Animal Health (OIE). However, the gas stunning section of the OIE slaughter guidelines is currently designated as “under study,” and the guidelines note that “inhalation of high concentrations of carbon dioxide is aversive and can be distressing to animals.” The guidelines further state that the use of nonaversive gas mixtures is being developed.

The International Coalition for Animal Welfare, of which AWI is a member, recently submitted a statement to the OIE urging the international body to prioritize a review of the use of different gas mixtures in the stunning of pigs. Research conducted in laboratory settings suggests that inert gases (argon and nitrogen) cause less distress to pigs than carbon dioxide. Unfortunately, under the current regulations of the Humane Methods of Slaughter Act (HMSA), CO2 is the only gas that can be legally used in the United States to stun pigs or other mammals for slaughter.

That may be changing, however. AWI supporter Lorna Moffat, who has worked to improve the slaughter of pigs for many years, recently requested that the USDA’s Food Safety and Inspection Service (FSIS) allow the use of inert gases for stunning. The FSIS notified Moffat that it will grant her petition, having concluded that the information she provided “supports the use of inert gases, such as argon and nitrogen, as a humane method of slaughtering and handling swine in connection with slaughter.” While the FSIS says it has no immediate plans to officially change the HMSA rules, it will allow companies wanting to use inert gases to request a waiver of the current regulation that limits the use of chemicals for stunning to CO2.

The FSIS considers the use of inert gases for stunning pigs to be new technology, and has indicated that it will issue waivers for research so that testing of the new technique may be facilitated. The next step in the process will be to pressure major US pork companies to commit to transitioning—or at least testing—a switch from CO2 to less distressful inert gases for stunning pigs.