BioCycle August 2008, Vol. 49, No. 8, p. 45
Study examines litter composting and reconditioning as a means of managing persistent disease problems in the commercial poultry industry.
Gary A. Flory, Robert W. Peer, Becky Barlow and Doug Hughes
LITTER reconditioning has had limited use within the poultry industry as an alternative bedding practice since the 1980s. Litter reconditioning – also known as composting, windrowing, pasteurization and recycling – is a process of composting litter between flocks to extend the life of the bedding material. Interest in litter reconditioning has grown in the last few years as the cost of quality bedding material has risen and the availability decreased. However, this single consideration was not sufficient to cause widespread application of this alternative bedding method.
Today, a number of additional factors are causing the commercial poultry industry to take another look at litter reconditioning. These factors include decreased use of antibiotics in poultry flocks, excessive litter in areas of high poultry production, increased concerns about pathogens in litter used as fertilizer and environmental concerns related to the storage of poultry litter.
MATERIALS AND METHODS
A research study was conducted in October 2007 to evaluate litter reconditioning in terms of cost, pathogen reduction and bird health. A major goal of the project was to evaluate and compare the productivity of the birds grown in the experimental house versus the birds produced in the control house immediately following litter reconditioning. To ensure a valid comparison, the birds placed in both the control and experimental houses came from the same hatch. Data on feed deliveries, fuel usage, ambient temperature, processing and flock settlement were collected from each house.
A chicken broiler farm was identified for this study that had two identical 600-foot poultry houses. Each house contained approximately four inches of poultry litter evenly distributed throughout the house. In one poultry house the litter was managed utilizing a litter reconditioning strategy. The second house served as the control and was managed consistent with the farm’s existing litter management strategy – a process often called crusting that involves removing wet litter (cake) before bringing in the next flock. Both houses had concrete floors throughout the length of the houses.
The day after the chickens were removed from the houses for processing, a Brown Bear R24C aerator attachment on the front of a high-flow skid loader was used to aerate and mix the poultry litter in the experimental house and construct two windrows (which ran the length of the poultry house). Initially, three windrows were constructed by the aerator, but two were combined to evaluate if sufficient mass existed in a single windrow to generate adequate composting temperatures and control pathogens. The single windrow was approximately 30 inches tall and 5 feet wide. The combined windrow was approximately 42 inches tall and 7 feet wide.
The windrows were turned with the aerator four days after construction. Six days after construction, the windrows were spread out using a tractor-mounted scraper blade to prepare the house for the next flock of chickens. Fourteen days after the previous flock was sent to processing, new flocks of chickens were placed in both the control and the experimental houses. (Typical downtime between flocks is one to two weeks. Composting between flocks requires at least one week. The current trend in the industry is for two-week downtimes to reduce production.)
Both windrows in the experimental house were flagged at 10 locations approximately 60 feet apart. Temperatures within the windrows were sampled twice a day, beginning 12 hours after windrow formation. Temperatures were collected using 36-inch analog compost thermometers.
Bacteriological samples were collected at the flagged locations in the windrows, as well as in the control house (at the same 60-foot intervals). Samples were collected at each location three times throughout the composting process. Approximately two pounds of litter were collected at each sampling location and sent to a Virginia Tech laboratory to be analyzed for Salmonella, E. coli and total aerobic plate count.
Litter nutrient samples were collected as a composite of samples grabbed from flagged locations in both the control and experimental houses, and collected at the beginning and end of the composting process. Samples were analyzed by the Agricultural Service Laboratory at Clemson University for moisture, ammonium nitrogen, total nitrogen, phosphorus as P2O5, potassium as K2O and eight micronutrients.
Ambient ammonia levels in the poultry houses also were analyzed throughout the composting process in the experimental house as well as in the control house. Additionally, ammonia levels were analyzed during production of the first posttreatment flock. Levels were measured with a portable ammonia meter.
Analysis of the temperature data showed that the smaller windrow reached and maintained optimum composting temperatures almost as well as the larger combined windrow. The temperature goal of 135°F was met and exceeded in both cases. A temperature surge to above 140°F was noted immediately following windrow aeration at four days.
Large reductions in the bacteria levels within the litter bedding were observed in the experimental house when compared to the control house. This was true of the total aerobic plate count, E. coli and Salmonella. Figure 1 illustrates the reductions in E. coli during the composting process compared to the stable E. coli levels in the control house. Figure 2 illustrates similar results for the Salmonella data. Historically, testing levels of bacteria in the litter has not been done. Bacterial testing is only done on the birds/meat at processing and elevated levels can result in condemnation of the meat.
The difference in mortality between the experimental and control houses after the onset of the disease is illustrated in Figure 3, with considerably lower mortality in the experimental house. Daily mortality was logged in both the experimental and control houses. Analysis of this data shows mortality within the houses staying consistent until 17 days after flock placement. At 17 days, the flock began to show signs of the poultry disease Necrotic enteritis. Enteritis is caused by the obligate anaerobic bacteria Clostridium perfringens, which is commonly found in soil, dust, feces and feed and is a normal inhabitant of the intestines of healthy chickens. Historically, Clostridium perfringens was managed through antibiotics delivered in the feed. However, the trend in the poultry industry – driven by consumer demand – is the reduction or elimination of antibiotics in commercial poultry. This trend has meant that the management of enteritis, and other common poultry diseases, is more critical now than in the past.
Heat for the poultry houses was provided by propane furnaces. Analysis of propane usage indicated that the experimental house used approximately 350 gallons more propane than the control house. This was due to the increased need for ventilation caused by higher ammonia levels in the experimental house. Increased ventilation requires more energy to replace the lost heat when exhausting the warm air from the houses. The increased ammonia level was a result of mixing the litter during windrow construction and the retention of the high moisture litter (cake), which would normally be removed when crusting (machine removal of caked litter).
Perhaps the most dramatic result of the study is the comparison of the two flocks of birds when they were processed as shown in Table 1. The flock in the experimental house had a greater average weight, grew larger on less feed (i.e., better feed conversion), greater livability and less condemnation. This resulted in the production of 8,553 more pounds of poultry meat.
The traditional litter management program requires the complete removal of all litter once every year or two to be replaced with three to four inches of fresh shavings. In between complete removal, fresh shavings are added only as needed (e.g., under the water lines in corners where birds congregate). Most operations get by without adding any new material. Fresh shavings to fill a 600-foot house cost about $2,400. However, replacing litter with shavings is not required with litter reconditioning. The production of over 8,500 pounds more chicken translates into a direct financial benefit to the poultry company and an additional $1,998 for the farmer.
On the negative side of the economic equation, the experimental house used more propane than the control house. Based on the price of propane in November 2007, the additional propane cost the producer approximately $700 more than in the control house.
Litter reconditioning requires the use of a skid loader or a skid loader aerator attachment such as the Brown Bear aerator used in this experiment. Crusting (wet cake removal) generally costs about $225/house when completed by a custom operator. Litter reconditioning by a custom operator would likely cost $300/house. In addition to the cost of the custom operator, the producer would need to level out the windrows with a tractor and blade at the end of the composting process. Cost of labor and fuel for this operation would be approximately $100/house.
Poultry producers who own their own skid loaders could save some of the cost of hiring a custom operator or purchasing aeration equipment by forming windrows with their own equipment. However, when using a skid loader to form windrows, there is still a need to use crusting equipment to remove the cake since the skid loader does not break up the cake as well as the aeration equipment.
With the cost of aeration attachments ranging between $15,000 and $20,000, it may not be feasible for individual growers to own one. Alternative business models for implementing the litter reconditioning strategy might include purchase of the aeration equipment by an industry group or an entity such as a local Soil & Water Conservation District. These organizations could then lease the equipment to individual farmers. Another possibility is that the integrated poultry company could purchase the equipment for use by its producers.
LONG-TERM MANAGEMENT STRATEGY
To be effective, litter reconditioning must be implemented as a long-term management strategy. A single treatment demonstrated its benefits, but multiple treatments during the production year may be needed to break the cycle of persistent poultry diseases. Timing of the treatments is critical to avoid increased energy cost. Our experiment demonstrated the economic benefits of better bird health but the economic advantages could have been increased by timing the treatments between late spring and early fall to minimize the increased heating cost.
Litter reconditioning has the potential to ease the impact of the shortage of bedding material. However, the real benefit of this litter management strategy is in its potential to help manage persistent disease problems within the commercial poultry industry. Safe, cost-effective disease management strategies are becoming more important as the use of antibiotics in commercial poultry production decreases or is eliminated.
Also, the environmental and health benefits of litter reconditioning appear to be significant when litter is land applied as a soil amendment. The reduction of pathogens in land applied litter can minimize the negative impact on grazing animals, as well as the potential for impacts on humans and aquatic life from application field runoff.
Gary A. Flory is Agricultural & Water Compliance Manager for Virginia Department of Environmental Quality (DEQ), and can be contacted at firstname.lastname@example.org. Robert W. Peer is Agricultural Program Coordinator for Virginia DEQ, and can be contacted at email@example.com. Becky Barlow is Organic Resources Marketer for Shenandoah RC&D, and can be contacted at firstname.lastname@example.org. Doug Hughes is Agricultural Program Specialist for Virginia DEQ, and can be contacted at email@example.com.
August 20, 2008 | General
Poultry Litter Composting Aids Flock Management
BioCycle August 2008, Vol. 49, No. 8, p. 45