In the event of an infectious animal disease outbreak, rapid depopulation of the infected livestock herds can help prevent the spread of the disease and potentially reduce suffering of the impacted animals. There are several options for rapid depopulation; however, many methods require substantial labor inputs or specialized equipment, both of which may be difficult or expensive to procure. Delays in depopulation prolong the infection, spread of the disease, and suffering of the affected animals. An alternative method is ventilation shut down (VSD), where mechanical ventilation is stopped and all air inlets and outlets are closed. Ventilation shut down plus, VSD+, is an American Veterinary Medicine Association (AVMA) approved rapid depopulation method for swine in which VSD is implemented in conjunction with supplemental heat or chemicals to accelerate mortality. This project describes a flexible model developed to simulate VSD+ using supplemental heat in swine facilities. Results showed that without the use of supplemental heat it is not feasible to achieve greater than 95% mortality within 1 h of VSD for most conditions. Look up tables were developed that present minimum supplemental heat requirements based on body weight (10, 70, 130, 200 kg), air leakage (1.5, 3, 4.5 air changes per hour or ACH), and ambient conditions (-30°C to 30°C). Minimum supplemental heat requirements are also presented for typical facility designs at various stages of swine production. Supplemental heat requirement increased with decreasing pig body weight, ambient temperature, and air tightness. Additional supplemental heat was needed to achieve virus inactivation for the targeted African Swine Fever virus at 56°C for 70 min. Indoor CO2 concentrations and relative humidity levels are also presented. Results can be used by producers and governing agencies to prepare for and respond to emergency disease outbreaks when rapid depopulation of swine facilities is necessary.
For more information, please contact Dr. Brett Ramirez in the Department of Agricultural and Biosystems Engineering at Iowa State University; email: [email protected]
- A computer simulation tool was developed to model indoor conditions during ventilation shut down with supplemental heat (VSD+) to achieve rapid depopulation at virus heat inactivation (HI) in swine facilities.
- Results showed that for typical facility construction VSD alone was not sufficient in most scenarios to achieve greater than 95% mortality within 1 h per AVMA guidelines.
- Supplemental heat required increased with decreasing pig body weight, ambient temperature, and air tightness.
- Further supplemental heat was required to achieve HI for the targeted ASF virus, though pig body weight did not have as much of an impact for this goal. Resulting look up tables can be used by producers and governing agencies to prepare for and respond to emergency disease outbreaks when rapid depopulation of swine facilities is necessary.