Current design standards and operation guidelines for poultry mortality disposal methods do not adequately account for the non-steady production of carcasses on poultry farms. A common method is to assume poultry die at a constant annual death rate at the mean weight for a placement of birds. While this method may be an accurate estimation for relatively steady-state operations such as egg laying, it grossly overestimates mortality production at the beginning of a grow-out cycle and underestimates mortality production towards the end of a grow-out cycle for meat production operations such as broilers and turkeys.
An expert panel was convened by the Agricultural Working Group of the Chesapeake Bay Program to determine annual mortality, nitrogen and phosphorus masses produced by broiler, turkey, and laying operations in the watershed. This paper concentrates on the mortality masses estimations determined by the panel on a weekly and grow-out basis, using broilers as an example.
What Did We Do?
The weight of mortalities produced each week was determined by combining the expected weekly death rate with growth pattern for broilers. In other words, weight of mortalities collected each week in a grow-out period is equal to number of birds dying during the week times the weight of birds at the time of death. Mortalities collected for an entire grow-out period are then calculated by summing the weekly values. This method can be used to determine mortalities produced for any market weight of bird because market weight is determined by the length of grow-out – all modern commercial broilers having the same basic growth pattern.
What Have We Learned?
Figure 1 illustrates the average growth pattern of broilers using company-provided data for genetic lines commonly used in the Delmarva region. Figure 2 shows weekly mortalities for broilers based on a data set used by the USDA-NRCS in Delaware to design capacity of mortality freezers and industry data provided confidentially to the retired Delaware Extension Poultry Specialist. This death rate data is for antibiotic-free birds. Combining figures 1 and 2 gives the expected weight of mortalities collected by a farmer each week during grow-out per 1,000 broilers placed in a building (Figure 3). Figure 3 shows that weight of mortalities increases each week at an exponential rate with a high degree of correlation (R2 = 0.975).
Adding the weight of mortalities collected in one week to those collected in previous weeks gives the total weight collected up to date, or the cumulative weight of mortalities. Since the time required to raise a bird to a certain market weight is known (Figure 1), we can plot the cumulative weight of mortalities during a grow-out period versus market weight of broilers (Figure 4).
The estimated weight of mortalities collected each week and the cumulative weight of mortalities collected over a grow out period can be used to better design and operate mortality disposal methods.
A poultry farmer can use the maximum mass collected each week to accurately size a mortality incinerator or estimate the number of dead birds she will have to cover every day in a mortality composter. Multi-bin composters are usually designed to hold the entire mass of mortalities expected in a grow-out period – plus additional high-carbon and cover material. Designing for this capacity is now possible with an accurate estimate of mortality weight collected per grow-out period.
Douglas W. Hamilton, Ph.D., P.E., Extension Waste Management Specialist, Oklahoma State University
Corresponding author email address
Thomas M. Bass, Livestock Environment Associate Specialist, Montana State University; Amanda Gumbert, PhD., Water Quality Extension Specialist, University of Kentucky; Ernest Hovingh, DVM, PhD., Research Professor Extension Veterinarian, Pennsylvania State University; Mark Hutchinson, Extension Educator, University of Maine; Teng Teeh Lim, PhD, P.E., Extension Professor, University of Missouri; Sandra Means, P.E., USDA NRCS, Environmental Engineer, East National Technology Support Center (Retired); George “Bud” Malone, Malone Poultry Consulting; Jeremy Hanson, WQGIT Coordinator – STAC Research Associate, Chesapeake Research Consortium – Chesapeake Bay Program
Hamilton, D., Bass, T.M., Gumbert, A., Hovingh, E., Hutchinson, M., Lim, T.-T., Means, S., and G. Malone. (2021). Estimates of nutrient loads from animal mortalities and reductions associated with mortality disposal methods and Best Management Practices (BMPs) in the Chesapeake Bay Watershed. Edited by J. Hanson, A. Gumbert & D. Hamilton. Annapolis MD: USEPA, Chesapeake Bay Program (DRAFT).
Funding for this project was provided by the US-EPA Chesapeake Bay Program through Virginia Polytechnic and State University EPA Grant No. CB96326201
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