Ventilation shutdown

Ventilation shutdown (VSD) is a means to kill livestock by suffocation and heat stroke in which airways to the building in which the livestock are kept are cut off. It is used for mass killing — usually to prevent the spread of diseases such as avian influenza. Animal rights organizations have called the practice unethical. The addition of carbon dioxide or additional heat to the enclosure is known as ventilation shutdown plus (VSD+).

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