Using Carbon Dioxide to Euthanise Young Pigs

Carbon dioxide euthanasia offers a recognized option for terminating nursing and nursery-sized pigs that farm employees find acceptable, explains Jerry May, extension educator for Michigan State University.
calendar icon 13 February 2009
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"We are taught as livestock care takers to provide the correct environment and care to allow all animals to thrive and meet their productive expectations. But even when provided the best of care there will be instances when animals become ill or injured and must be humanely euthanized," writes Jerry May of Michigan State University.

The National Pork Board has three broad standards for determining when euthanasia is warranted. According to the Pork Board:

  • Animals showing no improvement, or having no prospect for improvement, after two days of intensive care should be euthanized.
  • Severely injured or non-ambulatory pigs with the inability to recover should be euthanized immediately.
  • Any animal immobilized, with a body condition score of 1, should be euthanized immediately.

In 2001, the Pork Board and the American Association of Swine Veterinarians (AASV) jointly published On Farm Euthanasia of Swine – Options for the Producers outlining the acceptable methods of euthanasia for all stages of pig production. This booklet has become the on farm euthanasia standard for many operations.

Many farms struggle with young pig euthanasia. Blunt trauma, carbon dioxide, electrocution and anesthetic overdose are all listed in the booklet as acceptable methods of euthanizing nursing pigs. Electrocution is seldom used due to worker safety concerns and anesthetic overdose is used only under the supervision of a licensed agent, making that method impractical.

Figure 1. An example carbon dioxide chamber

Recently, Mr May has had requests for information on boxes for using carbon dioxide (CO2) to euthanize young pigs. The On Farm Euthanasia of Swine booklet lists carbon dioxide as an acceptable euthanasia method for all pigs up to 70 lbs, making this an acceptable method for nursery pigs as well as small pigs in the farrowing barn. Mr May was able to find information on the operation of a carbon dioxide euthanasia device but very little on the practical side of building one on the farm, so he set out to put one together (Figure 1).

Carbon dioxide is heavier than air therefore the container does not need a tight seal, although the cover should be secured so that the pig is not able to lift the lid and try to escape. Once the carbon dioxide is released to the container, it will stay contained until the space is disturbed or the carbon dioxide is “dumped out”. Heavy plastic tote boxes or plastic garbage cans make excellent containers. Mr May chose to use a plastic tote box. He cut one hole in the lid as an inlet for the hose carrying the carbon dioxide, then two small holes on the opposite end as an outlet. The container should be the correct size for the stage of production it will be used in. For example, a 30-gallon capacity should be used for for nursery pigs.

Carbon dioxide is readily available where compressed gases are sold. Like acetylene and oxygen that you buy for your farm shop, carbon dioxide tanks are purchased under a lease/purchase arrangement and then returned and exchanged for refills.

Flow to the container must be controlled by a carbon dioxide control valve. The valve used was a Victor with a rated flow of about 500 cubic feet per hour (CFPH) at 10 pounds per square inch gauge (PSIG). The carbon dioxide valves for welding deliver a low volume – up to 5 CFPH – which is not adequate for this purpose.

Use a heavy rubber hose to transfer the carbon dioxide from the tank to the box. Frost will develop on the hose during use. Light hoses may crack or break under these conditions.

For nursing pigs, the recommended carbon dioxide concentration for euthanasia is 60 to 70 per cent with a five-minute exposure time. The suggested optimal inflow rate is 20 per cent of the container volume per minute. The container design should allow for it to be pre-charged with carbon dioxide. Pigs should be unconscious within 45 seconds and experience respiratory arrest within five minutes. (Morrow, 1995)

Using carbon dioxide is considered relatively employee-safe. Caution needs to be taken if the euthanasia box is located in a small enclosed work room. Carbon dioxide detectors, similar to smoke detectors, are available and should be installed if the unit is located in a tight space. Dead animals should be dumped from the container rather than picked out by the worker to avoid breathing in the carbon dioxide.

While everyone associated with raising pigs recognizes the need for painless and humane euthanasia of terminally ill or injured animals, most farm employees feel uncomfortable performing the task. Poor euthanasia practices can lead to employee dissatisfaction, poor performance and disrespect for healthy animals (Morrow, 1995). Carbon dioxide euthanasia offers a recognized option for terminating nursing and nursery sized pigs that farm employees find more acceptable.

Further Information

Euthanasia: Balancing Welfare, Safety and Convenience by W.E. Morgan Morrow, 1995, North Carolina State University.
On Farm Euthanasia of Swine – Options for the Producers, National Pork Board and American Association of Swine Veterinarians, 2001.
Alternative methods of euthanasia can minimize piglet suffering. 2001, Bob Friendship and Anne Deckert.
Euthanasia Update, 2008, Ohio Swine Health Update.
PQA Plus Site Assessment Workbook, National Pork Board, 2007, National Pork Board, Des Moines, IA 50306

February 2009
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