Emergency Depopulation of Caged Layer Hens using a Compressed Air Foam System and CO2 Gas

Weiher, Jaclyn
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University of Delaware
Outbreaks of avian influenza (AI) and other highly contagious poultry diseases continue to be a concern for those involved in the poultry industry. In the situation of an outbreak, emergency depopulation of the birds involved is necessary. Emergency responders have to select the best depopulation method that minimizes the spread of the disease and risks to human health but also addresses animal welfare concerns. The determination of time to unconsciousness is very important when selecting a depopulation method, as it shows when the birds are no longer aware of their surroundings or in any pain. The purpose of this experiment was to evaluate the efficacy of a compressed air foam system (CAFS) against traditional CO2 gassing in mass emergency depopulation of caged layer hens. The experiment was conducted using a randomized block design with commercial layer hens exposed to one of three randomly selected depopulation treatments: CAFS, CAFS with CO2 gas, and CO2 gas alone. The time to unconsciousness, brain death, and terminal convulsions were recorded for each bird. Unconsciousness and brain death were evaluated using the EEG signals recorded from a wireless transmitter surgically implanted into the brain of the bird. Terminal convulsions were determined through analysis of recorded data from an accelerometer attached to the layer’s leg during depopulation. Critical time for physiological events were extracted from the EEG and accelerometer data and were compiled in Excel and statistical analysis was performed using JMP. Statistical analysis methods included Fit Y by X analysis using ANOVA and a student's t test of means. All tests were conducted at the 5% (α = 0.05) significance level. There was a statistically significant difference in the time to unconsciousness between the two compressed air foam methods and the CO2 gassing. However, there was no statistically significant difference when comparing the two foams. CAFS with CO2 gas was the fastest treatment with respect to unconsciousness (μ=16.9 sec) with regular CAFS close behind it (μ= 19.5 sec). CO2 gas was significantly slower (μ= 38.5 sec). The time to brain death of the birds show there was no statistically significant difference between CAFS (μ= 131.1 sec), CAFS with CO2 gas (μ= 135.5 sec), and CO2 gas (μ= 142. 4 sec). The time to terminal convulsions of the birds showed that there was no statistically significant difference in the time to motion cessation for CAFS (μ= 211.4 sec), CAFS with CO2 gas (μ= 224.0 sec), and CO2 gas (μ= 226.4 sec). The results of this experiment show that a compressed air foam system was able to depopulate layer hens housed in cages and was more rapid at causing unconsciousness than CO2 gas. Though not statistically significant, the compressed air foam system caused brain death and motion cessation faster than CO2 gas. The time to unconsciousness was also more consistent for the two foam treatments, with less variation from the mean compared to CO2 gas. This information may play a role in how organizations such as the American Veterinary Medical Association (AVMA) and US Department of Agriculture (USDA) evaluate the suitability of a compressed air foam system for mass depopulation of caged layer hens.
animal science , emergency depopulation , Food Science