United Poultry Concerns June 30, 2005

On May 17, 2005 the Association of Veterinarians for Animal Rights and United Poultry Concerns sent the following letter to the state veterinarian of all US states.

Re: Mass Depopulation/Extermination of Birds to Control Disease

Dear Dr. _________

Because you could be placed in a position of having to decide whether to depopulate millions of birds to control an outbreak of avian influenza, we are writing respectfully to tell you of concerns within the animal protection community and to suggest an alternative procedure in case of an emergency.

As you are probably aware, the World Organization of Animal Health (OIE) and the United Nations Food and Agriculture Organization have concluded that the mass depopulation of birds is "not an acceptable method of control . . . for ethical, ecological and economic reasons." These organizations discourage mass depopulation because avian influenza is so widespread in wild bird populations that domestic birds will continue to be reinfected. The more effective solutions they propose are vaccination, biosecurity, and elimination of the intensive confinement conditions that spread avian influenza in domestic flocks.

But since mass depopulation remains the primary method that is used to check the spread of avian influenza and other infectious disease outbreaks in domestic flocks in North America, we are taking this opportunity to provide you with some information about alternatives to procedures that have been used, including burning, shredding, and burying birds alive, and suffocating them with carbon dioxide. The latter is the commonly used method. Typically, barns filled with chickens or other types of domestic birds are enclosed in large tents and filled with CO2. Because the tents (or the tarps that are often used to kill groups of birds inside the barns) are seldom airtight, and because the gas is not evenly distributed, birds tend to suffocate slowly and painfully over a period of hours.

But even in airtight chambers, birds suffer painfully in being exposed to CO2.

In a seminar given at the US Department of Agriculture in December of 2004, Dr. Mohan Raj, a Senior Research Fellow in the Farm Animal Division of the School of Clinical Veterinary Science at the University of Bristol in England, explained that CO2 induces breathlessness, or dyspnea in animals, including birds, and that dyspnea "activates brain regions associated with pain and induces an emotional response of panic." While CO2 increases the rate and depth of breathing to expel CO2 from the lungs, breathing increases the intake of CO2, and thus the desire to breathe to expel the CO2 causes slow, painful suffocation.

By contrast, he said that a gaseous stun/kill system based on the use of the inert gases argon or nitrogen, known as Controlled Atmosphere Stunning, eliminates or greatly reduces the suffering caused by pure CO2. Whereas CO2 induces painful suffocation, inert gases such as argon and nitrogen induce anoxia, resulting in a painless (or much less painful and distressing) death. The crucial difference, he explained, between anoxia and dyspnea is that, unlike anoxia, for which birds and mammals lack chemical receptors, suffocation involves receptors that register the physical separation of the upper respiratory tract from the outside atmosphere. In experiments in North America and the UK, chickens and turkeys exposed to high (40 percent or more) levels of CO2 "gasp, shake their heads, and stretch their necks to breathe." For these reasons, Dr. Raj has concluded that exposure to CO2 is "distressing and painful to animals and therefore should be avoided."

The rationale for using carbon dioxide instead of gaseous mixtures comprising nitrogen or argon (for example, 30% CO2, 60% argon, 8% nitrogen, and 2 % oxygen) is money. For example, a system developed in Alberta, Canada uses pure carbon dioxide in an enclosed chamber that can hold 650 end-of-lay hens at once. Yet this system could as easily, and much more humanely, use an argon- or nitrogen-based gaseous mixture to euthanize large groups of birds.

According to our information, carbon dioxide costs about $45-$65 per ton; nitrogen costs about $65-$80 per ton; and argon costs $300-$400 per ton. Because argon constitutes less than 1 percent of air by volume, and nitrogen is 79 percent of air, nitrogen is much cheaper and relatively close to carbon dioxide in cost per ton.

We hope that this information is useful to you and that in an emergency situation you will do everything possible to ensure that the most humane method of killing large numbers of birds at a time is used. We urge you to develop guidelines. Please do not hesitate to contact us at any time for more information.

Thank you for your consideration.


Teri Barnato, M.A.

National Director, AVAR

Karen Davis, Ph.D.

United Poultry Concerns

United Poultry Concerns, Inc.
PO Box 150
Machipongo, VA 23405-0150
FAX: 757-678-5070

(Battery Hens: Egg industry stalked by pressure to give its birds more room )

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