RALEIGH, N.C. — Rapid depopulation of poultry houses, during disease outbreaks, can be a challenge for producers. Adding heat and carbon dioxide (CO2) with ventilation shutdown could result in shorter times to death in layer houses, according to research conducted at North Carolina State University.

 

The researchers evaluated the time of death for endof-lay hens subjected to ventilation shutdown (VSD), VSD with added heat and VSD with added heat and CO2. The time of death was longest for VSD alone, at 91 minutes, and VSD did not result in a 100 percent euthanasia rate.

“VSD by itself is not as effective as it needs to be,” said Ken Anderson, NC State poultry scientist, who led the research.

A shorter time of death, 54 minutes, was found for VSD with heat. The time of death was shortest at 12 minutes for VSD with heat and CO2. However, the researchers found little difference in the time of death between these two methods when they scaled up the research to a room sized for a group of 144 end-of-lay hens.

“There was a 10-minute difference between VSD heat and VSD with CO2,” said Anderson.

He explained the key to applying the research on a chicken farm, in the event of a disease outbreak, is to seal the chicken house from air loss or entry, such as around ventilation fan openings. Improper sealing could lower temperatures and result in longer euthanasia times. “The building has to be real tight,” he said. The only additional materials that would be needed for VSD with heat are portable heaters that can blow heat into the building.

The needs for adding CO2 to a building are more extensive. “Our estimate is you would need two semi loads of CO2 in order to depopulate a typical U.S. layer house,” said Anderson.

In addition, workers would need to use a self-contained breathing apparatus, and CO2 monitors would have to be placed outside of the chicken house to ensure safe air quality where people are working.

The research, funded by the U.S. Poultry & Egg Assoc. (USPOULTRY), was cited in the 2017 draft of the American Veterinary Medical Assoc. Guidelines for the Depopulation of Animals. That draft classified ventilation shutdown as “Not Recommended,” while VSD with heat and VSD with CO2 are recommended depopulation methods.

Some animal welfare groups criticized the use of ventilation shutdown to depopulate poultry houses during the 2015 highly pathogenic avian influenza, or HPAI, outbreak. Groups including The Humane Society of the U.S. (HSUS) advocate conscious poultry should not be exposed to temperature rises that may cause bird stress.

“The new research, which found that the so-called most humane methods still took between 12 and 54 minutes of baking the birds alive before they perished, seems like it leaves much to be desired,” said Paul Shapiro, HSUS vice president of Policy Engagement, in a statement emailed to Farm World.

The NC State researchers also evaluated stress in the laying hens by testing the hens’ blood for levels of heat shock protein 70. The levels of HSP70, for hens exposed to stressors such as heat, humidity or CO2, declined in the VSD and VSDH environments. This may be because of longer times of unconsciousness for those hens, according to the research summary.

The research was funded in October 2015 with a $550,000 emergency grant from USPOULTRY, which sought to identify improvements in depopulation methods after the HPAI outbreak.

“Current depopulation methods, including CO2 kill carts, CO2 injection and fire-fighting foam, were quickly overwhelmed and prolonged the suffering of infected birds,” said Anderson, in his report to USPOULTRY.

A copy of the final research report, Evaluating Hen Behavior and Physiological Stressors During VSD for the Development of Humane Methodologies for Mass Depopulation During a Disease Outbreak, is available at the USPOULTRY website, www.uspoultry.org