What is the fine-grained topic of the following text: The time to physiologic states was evaluated for broilers, layer hens, turkeys, and ducks, comparing water-based foam and CO2 gas using electroencephalogram (unconsciousness and brain death), electrocardiogram (altered terminal cardiac activity), and accelerometer (motion cessation). Only return the topic.
Comparison of Water-Based Foam and CO2 Gas Effects on Physiological States of Poultry Species