Marketing considerations are often the deciding factor when egg producers and other poultry growers begin to design a mortality management practice for their operations. Chickens, like other animal species, have determined life cycles, but all chickens return eventually as elements to the earth from which they came. How we handle their “remains,” especially when large quantities are involved, is at least partly related to whether they can be recycled, traded, or sold for additional use.
Would further processing of spent hens and other farm mortalities yield additional products or value-added components of products? Many growers, other agricultural groups, and market analysts believe they do.
If no markets exist, and assuming for discussion that all other considerations are equal, then traditional methods (e.g., composting and incineration) may be the best management practices to facilitate the decomposition process. Such practices, when appropriately designed and operated, are effective and safe. To ensure safety, these procedures are stringently regulated.
Where markets for the processed by-products do exist, such as at feed mills, then newer practices (e.g., refrigeration, fermentation, and eventual
rendering) are perhaps the most efficient methods for disposing of spent hens and other farm mortalities. Rendering is costly and usually feasible only at capacities that usually exceed the grower’s or processor’s normal production cycle. Alternative technologies can provide ways for growers and their companies to deal with these materials without having to send them (usually at a negative cost) to distant renderers.
Fermentation and composting are discussed in fact sheets PMM/2, 3, and 6. Other methods currently being developed by commercial manufacturers, agricultural research programs, and processors include new grinder/mixers to enhance the fermentation process and dry extrusion systems.
Feather Removal
Feathers on carcasses are a problem for renderers. The feathers, which constitute about 10 percent of the body on a dry weight basis, cannot be digested by nonruminant animals and dilute the nutrient concentration of hen poultry meal. Feathers also absorb cooking fat, which makes the cooked product difficult to handle. Removal of the feathers by hydrolysis (cooking the fowl at high temperatures, pressure, and humidity) also degrades the quality of the other proteins. If the spent hens could be plucked before the rendering process, then virtually any renderer could accept the product for processing. Thus, a variety of methods are being tried to determine whether picking the birds can be successfully performed at the renderers.
Experiments to date suggest that carcass feathers can be successfully removed up to 24 hours post-mortem, using a batch scalding and picking system. Scalding bath time and temperature must be carefully monitored and calibrated to the carcass temperature to prevent overscalding and thus fixing the feathers in their follicles. It also appears that the amount of time a bird is taken off feed does not make the process any more or less difficult, and the feathers remaining on the carcass constitute about 0.1 to 0.2 percent of the total picked body mass. If, therefore, renderers de- termine to install a simple feather picking facility, they will be able to process unlimited numbers of spent hens without compromising their product’s quality or their production schedules.
Another promising line of feather research suggests that a feather-degrading bacterium and its enzyme keratinase will soon make it possible to convert feathers into a digestible feed protein. If ground feathers can be converted into amino ac- ids and peptides, poultry mortalities in general would have greater markets, since, at present, feathers detract from the marketability of the carcass. Feathers, like human and animal hair, are made of a keratin protein that is resistant to digestion. About one million tons of feathers (and another million tons of animal and human hair) are produced each year. The keatinase must be purified by the feather-degrading strain of Bacillus licheniformis, and then used in a bioreactor. This process is still being tested.
A Note on Grinders
The new grinders are basically automated portable machines that can be used to grind up the mortalities — depending on the model, the machine can be used for broilers, large poultry carcasses (i.e., turkeys), and even hogs. The material is then transferred to a fermentation storage tank and kept on farm until ready for use. The flow rate depends in part on the size of the mortalities; the smaller models handle approximately 75 pounds per minute, the larger ones may have a flow rate as high as 300 pounds per minute. The complete system has a grinder, catalyst mixer, and a material transfer pump (see PMM/6 for a description of the uses and benefits of this management practice).
Dry Extrusion
The dry extruder was developed in the 1960s to process soybeans and grains. In this process, friction is used to generate high temperatures and pressure in a very short time. High temperatures are reached in as few as 30 seconds, and pressure quickly builds to 40 atmospheres. Under pressure, the cells rupture, that is, their contents extrude (are forced out), which frees the moisture in them. The product can then be heat-dried to a minimum moisture of about 10 percent before the product is cooled and stored.
Thus, the birds are cooked, sterilized, and dehydrated almost immediately. Until recently, the high moisture content of poultry by-products prevented the completion of the dehydration process without serious loss of the product’s nutrient value. But in the extrusion process, the poultry by-product can be diluted with corn, wheat middlings, or soybean meal. The result is a partially dehydrated nutrient-rich mixture that is 50 to 60 percent poultry by-product and 40 to 50 percent a dry ingredient of choice.
The products are marketable, for example, as a feed component for layers or as a protein supplement for broilers. Universities report that the extruded product produces outstanding results when fed to other broiler chicks, layers, and turkeys. Analyses performed on various dry-extruded products, including whole spent hens, turkeys, and broilers at different ages and treated and untreated feathers, indicate that the nutritional value of these products is comparable to, or better, than corn/soybean meal diets.
Microbiological analyses also support extrusion as a safe complement to the rendering process. Before and after extrusion tests indicate that the high heat and pressure are sufficient to dispose completely of aerobic microorganisms even if they were present in the birds prior to processing. In one test, avian infectious disease agents, such as Salmonella typhimurium, Coccidia, turkey rotavirus, and others, were added to the poultry by-product before extrusion. After extrusion, tests for these organisms were negative, and the turkeys fed this product likewise showed no visible signs of disease lesions and no viruses in their intestinal tracts.
The Feasibility of Extrusion
The process of dry extrusion begins with finding a way to bring the product safely to the extrusion facility where it can be mixed with the dry ingredient of choice. Then the mixture is cooked in the extruder, moved to the thermal dryer, cooled, and removed to a final storage bin. This method has been tested, developed, and implemented as a complement to rendering. Commercial operations exist in the United States, Canada, Poland, and other countries.
Its feasibility depends on (1) the volume of the by-product available for processing and its value to the operation without further processing, if any; and on (2) how the finished product will be used, that is, what exact moisture content and nutritional value is suitable for the final product market. Answers to these questions make it possible to determine which dry ingredient should be added to the poultry by-product and whether the cost of production can be justified.
References
Blake, J. P. 1998. Upgrading the Value of Mortality Residues. National Poultry Waste Management Symposium Proceedings. Fayetteville, AR.
Kim, W.K. and R.H. Patterson. 1998. Recycling Mortalities by Using a Feather-digesting Enzyme or Sodium Hydroxide Treatment and Fermentation. National Poultry Waste Management Symposium Proceedings. Fayetteville, AR.
Lin, X., J.C.H. Shih, and H. E. Swaisgood. 1996. Hydrolysis of Feather Kenatin by Immobilized Keratinase. Applied and Environmental Microbiology 62(11): 4273-4275.
Middleton, T.F. 2000. Evaluation of Mortality Processing Alternatives. National Poultry Waste Management Proceedings. Ocean City, MD.
Reynolds, D. 1990. Microbiological Evaluation of Dead Bird Meal. Presentation at a Midwest Poultry Federation Education Program, Minneapolis, MN.
Rich, J. 1994. Alternative Markets, Scheduling, Transport, and Handling of Spent Hens. National Poultry Waste Management Symposium. Athens, GA.
Ruszler, P. L. 1994. Utilizing Spent Hen and Normal Flock Mortality. National Poultry Waste Management Symposium. Athens, GA.
Said, N. W. 1996. Extrusion of Alternative Ingredients: An Environmental and a Nutritional Solution. Journal of Applied Poultry Research 5:395-407.
Webster, A. B. and D. L. Fletcher. 1996. Feather Removal from Spent Hens up to 24 Hours Post-mortem. Journal of Applied Poultry Research 5:337-346.