Mass Depopulation of Poultry as a Disease Control Method

On June 21, 2006, the US Department of Agriculture’s Animal & Plant Health Inspection Service’s Animal Care unit sponsored a meeting on Methods of Mass Depopulation of Poultry. Each nongovernmental organization attending the meeting was asked to submit a summary of their recommendations on how the Department should proceed with its influenza planning in regard to mass depopulation of poultry. Below is United Poultry Concerns’ submission. Please note that United Poultry Concerns did not “recommend” any method of mass “depopulation” (extermination) of chickens and other domestic fowl.

The US Department of Agriculture is preparing for an H5N1 avian influenza infection of US poultry flocks, although to date no US outbreak of this subtype have been reported. Prevention and handling of H5N1 are said to include wild bird and live markets surveillance, biosecurity and possible vaccination; however, a primary emphasis is being placed on the mass extermination of poultry flocks, which is the poultry industry’s traditional response to transmittable diseases and is financed mainly through government funding. For example, the Delmarva Emergency Disease mass-extermination plan calls for each poultry company to absorb the first $100,000 and for each state thereafter to provide up to $5 million.

Unfortunately, it is unlikely that government-industry will take the initiative to remedy the living conditions that predispose poultry to a broad range of virulent diseases including the HPAI (Highly Pathogenic Avian Influenza) viruses. Government has likewise indicated that it will not shut down live poultry markets, although this would appear to be a prudent step consistent with the recurrent poultry disease epidemics in which live bird markets are implicated, and with the dire warnings of imminent human pandemics of avian influenza issued by governments around the world. Mass exterminations of flocks will accordingly continue to be part of a system that by its very nature incubates and spreads diseases.

In 2006, two government meetings on mass depopulation of poultry were attended by members of the animal protection community by the time of this writing: The “National Training Program on Procedures for Mass Euthanasia and Disposal Options for Catastrophic Poultry Disease Events,” hosted by the UC Davis Veterinary Medicine Extension at the Stanislaus County Agricultural Center in California on May 30; and “Methods of Mass Depopulation of Poultry Meeting” hosted by USDA-APHIS/Animal Care in the USDA Building in Riverdale, Maryland on June 21. The latter meeting included a request for nongovernmental organizations in attendance to submit recommendations on how the USDA should proceed with its influenza planning in regard to mass depopulation of poultry.

At the June 21 meeting it was pointed out that “no current field methods meet the true definition of ‘euthanasia.’” Indeed it is unlikely that mass extermination and euthanasia – a humane death – could be reconciled under any circumstances. The task of animal protectionists therefore is to urge government-industry to adopt the least inhumane methods of exterminating (“depopulating”) birds – such methods as could reasonably be assumed to cause the least amount of terror, pain and panic in birds, avoid asphyxiation (suffocation), paralytic electric shocks, and other extreme cruelties, and reduce to the barest minimum the time taken for birds to become irreversibly unconscious.

Dr. Mohan Raj of the University of Bristol’s School of Clinical Veterinary Science has insisted in his lectures and published papers that carbon dioxide (CO2) is inhumane. CO2, he has said, “induces breathlessness, activating brain regions involved in the perception of pain” (“Poultry Stunning and Slaughter Seminar,” USDA, 12/16/04). However, CO2 will no doubt continue to be used in mass exterminations because it is cheap and readily available. CO2 is used in whole-house killings and it is also pumped into containers filled with smaller groups of live birds from the poultry and egg industry – barrels, sealed dumpsters, and Modified Atmosphere Killing carts.

Another system under consideration for exterminating floor-raised birds is firefighting foam. Foam is said to be less labor-intensive than the conventional method of covering the birds with plastic tarps and pumping CO2 under the tarps. Foam is said to require 2 to 3 workers versus the 15-20 workers needed to implement the plastic tarp CO2 method. Many birds suffocate and/or die of heat stress while the tarps are being laid down and secured, and in whole-house gassing, workers have been said to walk on top of the tarped live birds to turn on the CO2 cylinders. In “Evaluating the Use of Fire Fighting Foam in Mass Poultry Euthanasia” [sic], Dawson, et al. concluded that “There was no indication that using the fire fighting foam as a means of euthanizing was any less humane than a currently accepted CO2 polyethylene bagging procedure” (i.e., the standard plastic tarp-based procedure).

United Poultry Concerns is neither ethically nor scientifically in a position to “recommend” methods of mass-exterminating birds. We will therefore simply note some of the many welfare abuses and concerns identified by veterinarians and others, and reaffirm that if mass exterminations are to be conducted, they should be done in such a way as to reduce to an absolute minimum the unavoidable suffering of the birds, based on the most advanced welfare criteria, regardless of competing goals of cost savings and expediency.

The science presented by Mohan Raj indicates that compared to other forms of mass extermination being proposed or already in use, the inert gases, such as argon or nitrogen, “do not cause pain or distress.” (There’s a question whether the violent wing flapping of birds exposed to inert gas is a sign of conscious suffering; Raj argues that it isn’t.) Other methods, according to Raj, are in varying degrees aversive to the point of causing intense and protracted suffering in birds, and the subjective effects of firefighting foam are virtually unknown, although Raj has indicated that suffocation and severe pain and distress are most likely involved. He recommends that while the use of inert gases “has not been investigated for the purpose of whole house gassing,” such investigation “warrants immediate research and development.” In particular, he says in his written statement on behalf of The Humane Society of the United States (“Killing Poultry on Farms During Disease Outbreaks: Current Status and Recommendations”) that “we need to establish whether it would be possible to make poultry houses gastight, displace atmospheric air using inert gases and achieve less than 2% by volume of residual oxygen required to kill poultry.”

1. When carbon dioxide (CO2) levels approach 40% or higher, birds gasp, shake their heads, and stretch their necks to breathe, whereas in the presence of argon, there is said to be no sign of birds gasping or stretching their necks to breathe. The reason is that birds have chemical receptors in their lungs (intrapulmonary chemoreceptors) that are acutely sensitive to CO2 but are insensitive to the anoxia (lack of oxygen) and hypoxia (subnormal levels of oxygen.) induced by inert gases such as argon or nitrogen.

2. Carbon dioxide increases the rate and depth of breathing to expel the CO2 from the lungs, but breathing actually increases the intake of CO2, and thus the desire to breathe to expel CO2 causes suffocation, as when birds are buried alive.

3. Unlike anoxia, suffocation involves receptors that register the physical separation of the upper respiratory tract from the outside atmosphere resulting in dyspnea, or shortness of breath, which is experienced as a subjective distress in breathing.

4. In whole house gassing of birds with CO2, fluctuating gas concentrations and extremely cold temperatures to the point of freezing the birds has occurred, and birds have been injured due to high pressure jet stream administration of the gas. In “Killing Poultry on Farms During Disease Outbreaks,” Mohan Raj explains that carbon dioxide delivered into houses as liquid (as opposed to the vaporized form not commercially used or expected to be) “produces extremely low temperatures (could be as low as 50 degrees C or below zero) and some people are concerned that this could cause hypothermia in conscious birds. Another concern is the jet stream created by liquid carbon dioxide. . . . Inevitably, the noise and cold temperatures have the potential to cause panic among the flock and any bird coming in the way of the jet would be subjected to severe blow and injury. Under this situation, the possibility that live birds may be frozen to death could not be excluded.”

5. Exposed to CO2, birds will try to escape from under the tarps, and in a mass extermination of floor-raised brown egg-laying hens, described at the June 21 meeting, after 56 minutes of exposure to CO2, all birds still were not dead. In fact it’s a commonplace that following exposure to CO2, birds may appear to be dead who actually are still alive.

6. According to Mohan Raj in his HSUS report to USDA, “A mixture containing low concentration (20% by volume) of carbon dioxide in argon (welding gas mixture), which is better than using a high concentration of carbon dioxide on bird welfare grounds, is universally available in large quantities and should be used in containerized gas killing systems.”

1. Describing small trials using firefighting foam to mass-exterminate chickens, Bruce Webster of The University of Georgia stated in his presentation on June 21: “You saw a lot of escape behavior for 4-6 minutes. You saw the birds’ heads sticking out of the foam.” Eventually the birds were “worn out” with their “volitional struggle.”

2. Mohan Raj indicates in his HSUS report to USDA that firefighting foam, whether “created using air” or “created using gases,” causes suffocation and severe pain and distress in birds.

3. In his review of the report “Evaluating the Use of Fire Fighting Foam in Mass Poultry Euthanasia,” Eric Dunayer, VMD, pointed out in his letter of June 20, 2006, that despite the authors’ description of the foam as “humane,” they admitted it was “difficult to observe the birds once the chamber was filled with foam,” and therefore, according to Dunayer, “the assessment of the birds’ behavior once enveloped in the foam could not be accurately reported. The foam may also have muted sounds of distress that may have indicated the birds were suffering.”

4. Dunayer further pointed out in his letter the fallacy of equating immobility with unconsciousness and the uncertainty of knowing, without objective measurement, whether the convulsions of foam-enveloped birds were “‘involuntary’ or signs of conscious struggling.” He wrote: “It is certainly possible that the birds could have been immobilized but conscious and therefore awake while they suffocated. Without some objective measurement of brain activity (e.g. corneal reflex, EEG findings), it is impossible to be certain the birds were in fact unconscious.” (It was said at the June 21 meeting that EEGs shorted out in foam trials, so such measurements could not be made.)

5. Dunayer also observed in his letter that based on his review of the report it is impossible to determine the cause or causes of death of birds enveloped in the foam.

6. In a trial using turkeys described at the June 21 meeting, birds were reported flapping under the foam for up to six minutes. That did not necessary mean, however, that the birds were unconscious or dead when flapping ceased or appeared to cease. Necropsies showed hemorrhages in the tracheas of birds who died under the foam and “occlusion of the trachea by the foam” was cited as a serious welfare concern by Ruth Newberry of Washington State University.

The conditions under which commercial egg-laying hens are kept – in long rows of cages stacked in tiers of three, four or more cages to the ceiling – create welfare problems in addition to those affecting floor-raised birds, including the stress to the hens of being roughly handled in being transferred from the layer cages to containerized killing units. Even if firefighting foam could be shown to eliminate some of the welfare abuses inevitable in other types of mass extermination, it is unlikely that foam could be used in battery-caged hen facilities. The hens would have to be pulled out of the cages and placed on some sort of floor system which would entail rough handling, whereas one of the main benefits of foam according to its proponents is that it eliminates the serious and inevitable welfare abuses of handling. The loss of feathers and fragile bones from which battery-caged hens suffer makes them particularly vulnerable to bodily injury in being handled. With this in mind, we present for consideration Swedish veterinarian Lotta Berg’s email to the Animal Welfare Institute on July 5, 2006, who wrote:

“[M]y main question regarding CO2 gassing in cage barns would be the distribution of the gas, especially in multi-tier systems (more than 3 tiers of cages on top of each other). CO2 is a heavy gas, which means that it starts working from the bottom and up. It is vital to make sure that the gas concentration is high enough to ensure that also the birds in the top tier cages are properly and instantly killed. To achieve this, there should probably be small air outlets in the top of the building, to prevent ‘fresh’ air from becoming trapped up there under the ceiling and thereby stopping the CO2 gas from reaching all hens. It might also be worthwhile to consider using fans to circulate the air/gas in the house, to spread the gas more efficiently. These fans have to be separate, mobile fans (like the ones used on construction sites to dry concrete) which just create air movement, not the usual ventilation fans used to ventilate the building under normal conditions.”

Karen Davis, PhD, President
United Poultry Concerns, Inc.
12325 Seaside Road, PO Box 150
Machipongo, VA 23405
Phone: 757-678-7875; fax: 757-678-5070
Email: Karen@upc-online.org.

United Poultry Concerns, Inc.
PO Box 150
Machipongo, VA 23405-0150
757-678-7875
FAX: 757-678-5070
www.upc-online.org

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