Latest Sonoma County front in avian flu crisis: How exposed farm-raised birds are killed

After Highly Pathogenic Avian Flu was detected at Weber Family Farms, the company turned to a practice called “ventilation shutdown plus heat,” or VSD+, to put about 115,000 birds to death.|

As the spread of a deadly strain of avian flu casts a pall over Sonoma County’s poultry industry, and opponents of concentrated livestock farming aim for a November ballot initiative that would limit if not eliminate many of those operations, the lives of birds on local chicken farms have become a subject of scrutiny.

And so have their deaths.

At least one of the county’s poultry farms has used a controversial method to dispatch its flock following an incidence of the virus. After Highly Pathogenic Avian Flu was detected at Weber Family Farms — the largest Sonoma County farm yet to be infected by the bird flu strain — on Dec. 18, the company turned to a practice called “ventilation shutdown plus heat,” or VSD+, to put about 115,000 birds to death.

The use of VSD+ has skyrocketed nationally during the bird flu outbreak that began about two years ago, and the practice is accepted by the U.S. Department of Agriculture, California Department of Food and Agriculture, and American Veterinary Medical Association.

But it is criticized as inhumane by many agricultural veterinarians and some lawmakers, and is highlighted by animal welfare activists who cite cases they say show animal cruelty in the livestock and poultry industry.

“There’s no great method to do this,” said Crystal Heath, an East Bay veterinarian who is a founding member of the group Veterinarians Against Ventilation Shutdown. “But VSD is the worst.”

Heath is right about the lack of elegant options when it comes to culling a flock of chickens or ducks. In addition to VSD+, the most common methods are asphyxiating birds with carbon dioxide — either by injecting the gas into an enclosed structure or, more commonly, going cage by cage with a CO2 cart — and spraying them with a version of firefighting foam.

Smaller operations still use tried-and-true farm practices like “cervical dislocation” — snapping the neck — and gunshot.

“There’s nothing about what we had to go through that’s enjoyable,” said fourth-generation poultry farmer Mike Weber, co-owner of Weber Family Farms and a nearby egg facility, Sunrise Farms, that also had to kill exposed chickens. “You see the birds suffering, and you wish there’s something else we could do. There wasn’t.”

Mike Weber is co-owner of Weber Family Farms, which was devastated by an avian flu outbreak. The ranch had to destroy 550,000 chickens and 3.2 million eggs because of the avian flu. Photo taken in Petaluma on Tuesday, Jan. 9, 2024. (Christopher Chung / The Press Democrat)
Mike Weber is co-owner of Weber Family Farms, which was devastated by an avian flu outbreak. The ranch had to destroy 550,000 chickens and 3.2 million eggs because of the avian flu. Photo taken in Petaluma on Tuesday, Jan. 9, 2024. (Christopher Chung / The Press Democrat)

Ventilation shutdown with no additional components — that is, sealing up airflow in a poultry house, shutting off fans and waiting for birds to overheat and die — can take four hours or more to accomplish its somber task. And it does not always result in 100% lethality, a regulatory standard.

For those reasons, VSD alone is not recommended by the USDA. That’s where the “plus” comes in. It can be the introduction of either heat (raising the ambient temperature to 104-110 degrees, resulting in faster hyperthermia) or carbon dioxide (resulting in asphyxiation).

The government allows VSD+ because it can be deployed quickly, preventing birds at other farms from being exposed to the virus.

That is pertinent in Sonoma County, where 10 poultry operations, ranging from boutique duck farms to large egg-laying operations, have been hit by avian flu in just over two months. More than 1.2 million birds have been destroyed to prevent further contamination within the county’s nearly $50 million egg and poultry industry.

Workers tend to compost piles at Reichardt Duck Farm in the rolling hills of Two Rock, west of Petaluma, Friday, Dec. 1, 2023. (Kent Porter / Press Democrat)
Workers tend to compost piles at Reichardt Duck Farm in the rolling hills of Two Rock, west of Petaluma, Friday, Dec. 1, 2023. (Kent Porter / Press Democrat)

Ancillary businesses like fertilizer companies and feed mills are also being affected and the Board of Supervisors in December declared a local emergency amid the widening crisis.

Sarah Van Mantgem, the co-founder of Farm Animal, Climate & Environmental Stewards of Sonoma County, was unmoved, saying she was “heartbroken” when she learned a county poultry farm had resorted to VSD+.

“Avian influenza has been a known threat since 2015,” said Van Mantgem, who lives in Windsor. “Why have they not put plans in place to do the responsible thing and end the lives of their birds in a less cruel way?”

What sets VSD+ apart from other forms of depopulation, its critics say, is how long it takes the animals to die. Those other strategies may be gruesome in their way, but death tends to come within 15 minutes, if not instantaneously.

VSD+ takes substantially longer.

“Under experimental conditions, VSD + (Heat) caused 100% mortality of laying hens in two hours, however, when applied under commercial conditions, the VSD + H protocol required 4.5 h until no chickens were observed standing,” according to a study published in the peer-reviewed journal Animals in January 2023. “In turkeys, research shows it takes 50% longer for birds to die of VSD +H compared to laying hens.”

The article added that, according to state records, “in practice, VSD+H may be carried out for over 8 (hours) and still achieve less than 100% mortality.”

Negative effects associated with heatstroke include pain, overheating, nausea, malaise, anxiety, fear and thirst, the study authors wrote. Among the clinical consequences are gastrointestinal bleeding, acute respiratory distress syndrome and brain injury.

Those results are not lost on Weber. But VSD+, he said, was his best chance at preventing further catastrophe.

“When you’re in that situation, the only objective is to have all the birds dead,” Weber said. “That’s the only way you can save the next farm or the next person with a backyard flock, or someone down the street with an animal that could get affected. It’s bad enough to watch all the birds die. It’s another to be under immense pressure to put them down as soon as possible.”

Though animal scientists have been studying ventilation shutdown for at least 15 years, the practice was an outlier during the previous wave of Highly Pathogenic Avian Influenza, or HPAI, in 2014-15. That outbreak resulted in the death of 50 million chickens and turkeys in the United States, at more than 224 farms and backyard operations, but VSD was used to depopulate in only four instances.

The frequency had increased to more than 50% of all U.S. depopulations between January and August 2022, USDA records indicate.

The reasons are many. They include difficulty in acquiring concentrated carbon dioxide quickly and the proliferation of chicken houses with stacked cages, which makes foam less effective because it settles to the bottom, Crystal Heath said.

But the main driver of VSD’s sudden popularity is desperation. During the avian flu outbreak of 2014-15, those other methods did a poor job halting the virus as it jumped from farm to farm. As a result, the federal government developed a standard of killing birds within 24-48 hours of a positive test.

“There is strong evidence that a delay in depopulation results in an exponential increase in the total amount of HPAI virus shed into the environment by infected poultry,” the USDA wrote in a 2019 policy paper on VSD+, arguing that it should be considered if carbon dioxide carts or firefighting foam can’t be implemented effectively within 36 hours.

The American Veterinary Medical Association lent credence in 2019, recommending that VSD+ be “permitted in constrained circumstances” — basically, as a last resort.

“The primary factor for this recommendation is time,” the California Department of Food and Agriculture explained to The Press Democrat through a representative. “Some houses were never designed to allow for rapid removal of flocks because under normal circumstances they are removed in separate groups in periods of time ranging from weeks to months.

“If an infected flock were to be removed this slowly, not only would the flock suffer, but other flocks would also likely become infected. So, our team looks at the house and in rare instances, will agree to use VSD+ to meet the virus containment goal of rapid culling.”

The strategy may be working. The USDA’s Animal and Plant Health Inspection Service reported that faster depopulation, combined with better biosecurity, decreased farm-to-farm transmission in 2022.

When avian flu came to Weber Family Farms, Mike Weber said, they employed VSD + Heat to cull 115,000 birds in two of his chicken houses, out of a total of 500,000 that had to be dispatched. The rest were killed by cervical dislocation, according to the USDA data.

Weber Family Farms’ depopulation effort was “99% effective within two hours,” Mike Weber said, speaking of the farm’s use of VSD+.

The USDA and California Department of Food and Agriculture both signed off on Weber’s plan, and the state sent a veterinarian to oversee the process.

Weber noted that well over 100 poultry buildings have been infected during Sonoma County’s outbreak, which started the week of Thanksgiving, and that VSD+ used in only two. He called it evidence of the local industry’s desire to treat their animals as humanely as possible.

Van Mantgem is unmoved, insisting chickens and ducks mean nothing more than money to poultry farmers.

“Because of the indemnity payments for the depopulated birds, there is no incentive to do anything better,” she said. “It’s a closed system designed for one thing only: maximizing profits.”

Weber Family Farms has been earmarked for an indemnity payment of $4.8 million from the federal government to compensate for the loss of income, according to USDA data. Six other local farms, which could not be positively identified, will receive anywhere from $500,000 to just under $2 million.

The European Union’s Food Safety Authority advises that VSD+ “must never be used.” And two dozen members of Congress, including current Senate candidates Katie Porter and Barbara Lee, sought to discourage the practice in a May 2020 letter to then-U. S. Secretary of Agriculture Sonny Perdue, calling it “inhumane, distressing, and painful for the animals who can take many hours to die.”

Veterinarians Against Ventilation Shutdown submitted a petition to the American Veterinary Medical Association in 2022, urging the association to move VSD+ from the “under constrained circumstances” category to “not permitted” for mass culling. The organization collected the signatures of more than 2,000 licensed vets, Heath said.

The association rejected the petition and did not allow a vote.

The next step for Veterinarians Against VSD, according to Heath, will be a campaign to ask companies to sign a document pledging to form a plan for less cruel methods of depopulation.

“I hope Weber Family Farms, Reichardt, Petaluma Poultry and others will sign onto the pledge,” she said, referring to some of the better-known Sonoma County producers. “All of these corporations, along with the local, state, and national farm bureaus, have a lot of political power; I wonder why they aren't pushing these agencies to help them put plans in place to use less cruel methods.”

Heath thinks there needs to be an open conversation around VSD+, rather than retaliation against farmers.

Weber is certain activists will attempt the latter, especially as they gather signatures for a ballot initiative that would limit the scale of Sonoma County livestock and poultry operations such as his.

He believes the anger is misplaced.

“If there was a means to put down the flock that’s infested, faster and more humanely, there isn’t anybody I know who wouldn’t utilize it in this situation,” Weber said. “This has nothing to do with how we operate. It has to do with protecting the food supply. Sometimes when you’re fighting a fire, you have to light a backfire to stop it.”

You can reach Phil Barber at 707-521-5263 or On X (Twitter) @Skinny_Post.

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