ST. PAUL, Minn. -- Increases in the cost of replacement bedding materials, a limited supply of materials with which to bed poultry houses and restrictions on spreading litter have led to increased reuse of litter in many areas of the country.
Many broiler producers are completing a total cleanout of their broiler houses once every two to three years. Along with this litter reuse has come an increased need to effectively manage litter through a variety of techniques to maintain house conditions and bird health.
Poultry house management has continued to evolve to make the most of a lack of bedding materials.
Litter management
Litter reuse requires increased attention to ventilation and drinker management to maintain optimum house conditions for bird health and growth. Litter moisture must be maintained within a range that minimizes ammonia production and footpad burns while keeping dust within reasonable limits.
This can be difficult with the increased costs of heating suffered by broiler producers in recent years. The increased use of electronic house controllers has significantly increased a grower's ability to maintain a stable environment, thus improving house conditions. Attic vents also show promise to control litter moisture during cold weather as warmer air is brought into the house, increasing its ability to pick up moisture.
Downtime is an important factor in the management of litter (and bird health). Cutbacks in production that allow for longer downtimes do reduce the viability of litter microbes, leading to improved flock health. Recent movements towards double brooding implemented by some companies may allow for increased downtime in the fallow houses, improving flock health provided that brooding is managed carefully.
Proper water line management should be maintained through the use of chlorination, water acidifiers or other sanitizing chemicals. These programs must be designed to control bacterial load, while simultaneously preventing the formation of biofilms, which serve to protect bacteria from the action of sanitizing agents.
Like disinfectants used on surfaces, water-sanitizing agents should be rotated to prevent the formation of resistant populations. Growers in areas of hard water should be particularly careful when using any medications, which can in some cases be neutralized by the presence of minerals. Broiler litter is a community of microbes of different types. Properly balanced microbe populations help crowd out disease organisms and breakdown bird waste products.
In addition, used litter may expose broiler chicks to a wide range of organisms at low levels early in life, helping to prime the birds' immune systems. Normal bacterial levels in litter can be achieved and maintained with good litter management techniques, which serve to manage litter moisture, ammonia levels and pH.
Litter bacteria can be categorized into two large groups, those that produce spores and those that do not. In time, bacterial dynamics tend to form predictable patterns that are reflective of the type of operation (housing, animals, environment, etc.) and the quality of management. Non-spore forming bacteria increase with the presence of animals and the accumulation of their fecal material.
With time, litter bacterial levels tend to stabilize and become relatively constant as animals reach maturity, which is accompanied by stabilized gut microflora. Spore forming bacteria (such as clostridia) differ from non-spore formers in that their numbers tend to increase with time. Partial or complete cleanout may be necessary if diseases associated with spore-forming bacteria become chronic in a flock or house.
Composting
During the last few years, broiler producers have refined methods of in-house litter composting with the intent of using this technique to reduce bacterial and viral load between growouts. In most cases, growers use a box blade or composting machine to create one or two windrows in each house to allow the litter to go through a heat.
Cake may be left in to provide additional moisture for bacteria to proliferate if litter moisture is low. Temperatures of 130 degrees F or greater are needed to reduce bacterial numbers and kill fragile viral pathogens like LT.
Auburn research shows that maximum temperatures (130 to 150 degrees F) are reached within about 36 hours of windrowing and temperatures begin dropping after about 48 hours. This is long enough to kill most pathogenic bacteria and viruses. Based on this, a five day in-house composting program between flocks is a useful way to reduce viral and bacterial pathogens and improve bird performance. Litter should be spread out and allowed to release ammonia under minimum ventilation after windrow composting to reduce ammonia levels prior to brooding the next flock. If not, ammonia will be released at high levels as the house is heated prior to brooding. Some growers will use a tiller one or more times after spreading out the litter to reduce ammonia.
Although this technique would be useful in times of disease challenge to reduce the risk of disease in the next batch of birds, windrow composting also makes sense from an economic viewpoint. Reduced levels of fragile microorganisms such as LT and campylobacter helps to insure optimum bird performance and reduce human food safety concerns. Reduced loads of other harmful bacteria and viruses would allow birds to use feed for growth and performance rather than for fighting off mild (and often unseen) disease challenges.
High-speed tilling of litter has become a common method of conditioning litter between flocks. This technique may be used in place of cake removal, but more commonly is combined with cake removal to incorporate air into the litter and dry the litter prior to the next placement.
Tilling helps remove ammonia in addition to drying the litter. Tilling the litter should be performed several times between flocks to insure optimum results. Heat treatment of the litter through flaming has also been used to reduce bacterial levels in some areas of the U.S. This technique can help improve health through reduced exposure of day-old chicks to pathogens.
Litter treatments
Reduction of house ammonia levels is the primary purpose for using a litter treatment. In recent years, reasons for using a litter treatment and any potential benefits from its use have expanded to include improvements in performance and environmental concerns. Ammonia-reducing litter treatments offer a better in-house environment for the birds and may also play a role in reducing ammonia and odor emissions from poultry facilities.
Poor performance often shows up as underweight birds, poor feed conversion, high condemnations, or increased mortality. Some of these problems have been attributed to poor litter management, but also may be due to conditions of the soil in the poultry house. Birds excrete nitrogenous wastes in the form of uric acid.
Ammonia (NH3) is produced as a result of the microbial and enzymatic decomposition of these nitrogen-containing compounds. Once formed, free ammonia can be absorbed into the soil and long-term accumulation will result in an increased soil pH. In addition, ammonia concentration tends to increase with increasing pH. Liming the pad also produces long-term detrimental effects since it results in an increased soil pH.
Microorganisms such as bacteria, yeasts and molds can impact bird performance and disease status. They also have an optimum pH range in which they can survive when given a proper temperature and moisture level. Optimum pH ranges for bacteria, yeast and molds tend to be more alkaline (pH>7.0) than acid (pH<7.0). Optimum pH for viruses varies, but in general they are more sensitive to lower pH.
In poultry houses that have been in production for a prolonged period, pH of the soil tends to become alkaline in time and soil pH may range 7.1 to 8.5. This pH range provides an environment for disease-causing microorganisms. Keep in mind that normal soil pH ranges from 5.5 to 6.5 and provides an acidic environment in which these same disease-causing microorganisms do not survive. Sulfuric acid, when applied directly to the soil base in a poultry house, has proven to be effective in lowering pH of the broiler house floor to 5.5 or lower. The acid treatment is applied only to bare soil after clean out and before new bedding material is added. Typically, prior to application, strong ammonia odors are noticeable, but immediately upon application ammonia odors disappear.
The use of sulfuric acid can effectively achieve a lower pH of the soil of the broiler house floor, but care must be observed for its use. Sulfuric acid is considered a hazardous material and handling and transport of the material must meet strict guidelines. Transfer and mixing requires special precautions, since any accidental spillage may cause injury.
Another alternative is to employ a heavy dosing of the soil with one of the commonly available acidifying litter treatments at a higher than recommended rate. These rates may vary and could be double or quadruple the normal rate. In field studies, pH reduction of the soil often showed an improvement in performance of subsequent flocks.
Overall response to this route of treatment may also be related to conditions that existed prior to treatment. Keep in mind that soil treatment may not be 100 percent successful and may only account for a portion of the chronic problems that exist for an individual's situation.
In conclusion, litter management is an important part of keeping birds healthy and insuring profitability for a grower. Time and money spent in this area generally reaps positive rewards. Additional techniques, such as windrow composting, high-speed tilling and the use of litter treatments, may help keep reused litter from becoming a liability in terms of bird performance.
These additional techniques can only supplement, but not replace, good house management.
J.B. Hess, K.S. Macklin, S.F. Bilgili and J.P. Blake are with the Poultry Science Department; and T.A. McCaskey is with the Animal Science Department, all with Auburn University in Auburn, Ala. This article is drawn from material presented at the 2009 Midwest Poultry Federation Convention in St. Paul, Minn.
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