Efficacy and efficiency of poultry carcass composting using different mechanical mixing equipment for avian influenza outbreaks

Background and Aim: Avian influenza (AI) is a viral disease that caused the largest animal disease outbreak in the history of US agriculture. There are several disposal methods of AI infected poultry carcasses available in the US, which include on-site burial, landfill, incineration, rendering, and composting. Of these methods, composting is the most environmentally friendly and poses a low risk for biosecurity. The United States Department of Agriculture (USDA) has developed a comprehensive plan for composting AI infected carcasses. The current protocols have the potential for areas of anaerobic pockets within the windrow due to inadequate mixing and the large carcass size of whole birds. This could lead to ineffective virus neutralization or prolonged composting times and higher resource costs. The purpose of this project was to determine if using a horizontal mixer (HM) wagon to mix composting ingredients or a vertical mixer (VM) wagon to mix and cut up the compositing ingredients is an economical and timely means to accelerate the tissue break-down and obtain optimal temperatures for poultry carcass composting during an AI outbreak. Materials and Methods: A replicated trial with three treatments, HM, conventional layering (CL) and VM, and three replications was initiated at the Compost Research and Education Center part of the University of Maine Forest and Agricultural Experimental Station called High Moor Farm. Daily temperatures and screened core sample weights (screen weights) on day 0, 16, and 30 were recorded for each of the compost piles. The time to build each replication was recorded and used to help calculate the cost of each method. Data on equipment, carbon material and labor costs were collected from private contractors from the 2014 to 2016 highly pathogenic AI (HPAI) outbreak and used to compare costs between methods. Results: All treatment methods reached USDA protocol temperatures to neutralize the HPAI virus. Screen weights for both the VM and HM treatments were lower than the CL treatment. Screen weights decreased significantly from day 0 to day 16 for the VM and HM treatments with no significant change from day 16 to day 30. When comparing costs, the mixer wagon methods were the more cost effective than the CL method when using high volume equipment. Conclusion: The data from this study support the use of a mixer wagon to reduce particle size and mix ingredients for more timely and effective composting of poultry carcasses.