Ventilation shutdown involves sealing a shed by shutting air inlets and/or by turning off ventilation fans following which the birds’ body heat causes the internal shed temperature to rise. When this temperature is maintained for several hours it ultimately kills birds in the shed by hyperthermia (extreme heat) and hypoxia (suffocation) [1, 2]. Ventilation shutdown is inhumane as it causes prolonged suffering.
Why is mass killing of poultry required?
In the event of an avian disease outbreak, often the most effective way to contain the spread of the disease and reduce the human exposure to potentially zoonotic agents (diseases that can be transmitted between animals and humans) is to rapidly kill the infected flocks [3]. In this context, ventilation shutdown has been previously used as a simple method to kill infected flocks as it does not require any resources [4].
In countries such as the United States, the use of ventilation shutdown has been justified as a method of depopulation (removing birds from a poultry shed for the purpose of slaughter or humane killing) because approved methods for poultry depopulation were said to be ineffective in containing the last outbreak of Avian Influenza in 2015 [5]. However, it was also agreed that ventilation shutdown should only be used if the traditional methods of depopulation are unavailable.
What are the animal welfare issues with ventilation shutdown?
Ventilation shutdown causes prolonged suffering of birds before death. The effectiveness and time to death is variable depending on a number a factors, including the shed type, age and size of birds, the number of birds, the type of ventilation system, the ability to seal shed air inlets and environmental conditions like outside temperatures. In ideal conditions, it is thought that death in birds occurs in approximately 30 to 60 minutes [1, 2]. Birds are therefore subjected to excessive heat for a prolonged period before losing consciousness as well as the time to loss of consciousness (followed by death) being unpredictable given the shed conditions. This prolonged time to loss of consciousness and unpredictability is unacceptable when compared to other depopulation methods such as using gas or foam (see below) in which unconsciousness can be achieved in minutes.
The Australian Veterinary Emergency Plan for destruction of animals (AUSVETPLAN Edition 3.2) states that ventilation shutdown is an unacceptable method to depopulate birds given the animal welfare concerns and lack of scientific evidence around its effectiveness [6].
What are the alternatives of ventilation shutdown?
Currently, more humane methods of depopulation that have been used include gas (CO2) or high-expansion foam (water-based or gas-filled). RSPCA Australia believes that more research and funding is needed to develop and commercialise more humane, effective and practical methods to depopulate large numbers of birds during disease outbreak events.
What is the RSPCA’s view on ventilation shutdown?
RSPCA Australia is opposed to ventilation shutdown as a method of depopulation due to the serious animal welfare concerns.
References
[1] Eberle-Krish K et al (2018) Evaluation of ventilation shutdown in a multi-level caged system. The Journal of Applied Poultry Research 27(4):555-563.
[2] Zhao Y, Xin H, Li L (2019) Modelling and validating the indoor environment and supplemental heat requirement during ventilation shutdown (VSD) for rapid depopulation of hens and turkeys. Biosystems Engineering 184:130-141.
[3] Poultry Welfare (2016) How ventilation shutdown works in poultry depopulation.
[4] USDA (2016) HPAI 2014/15 confirmed detections.
[5] Green J (2015) Update on the highly-pathogenic avian influenza outbreak of 2014-2015. Congressional Research Service Washington, DC.
[6] Animal Health Australia (2015) AUSVETPLAN operational manual destruction of animals: a manual of techniques of humane destruction. Version 3.2.
