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In-house composting between flocks reduces viral and bacterial pathogens in the litter and improves bird health.
on June 23, 2009

Managing the ‘cleanout’ tradeoffs

Managing broiler litter should involve both the broiler company personnel and the grower

Managing litter quality is an important aspect of raising healthy broilers economically. Litter quality directly or indirectly impacts bird respiratory health, microbe numbers and viability, ventilation needs, propane usage and worker health. For these reasons, managing broiler litter should be an organized effort of both broiler company personnel and the broiler grower.

In the United States, broiler litter reuse for some period of time is the norm. Experience has shown that this system works well and has some practical advantages over cleaning out after each flock. In addition, environmental regulations have defined how farmers can use broiler litter as a fertilizer, forcing broiler growers to use and market their litter more carefully. Scarcity of suitable litter materials is an increasing problem in many broiler growing regions. Short pine shavings supplies and loss of other competing materials is making it expensive and/or difficult for growers to purchase materials for replacement after cleanout and to top dress.

In a given region, one or more of these situations may make frequent cleanouts unattractive. Fortunately, litter can be reused successfully if managed properly.

Used litter naturally exposes young birds to low numbers of many different kinds of microrganisms. This early exposure provides a type of competitive exclusion inoculation for birds such that they are less open (naive) to infection by pathogenic organisms. This assumes, of course, that substantial disease problems didn't carry over from the previous flock. Young broilers can be exposed to low levels of a variety of bacteria, coccidia and vaccine strains of viruses. Many operations that clean out litter after every flock experience more severe forms of common diseases because birds reach later ages in a naive state before being exposed to a pathogen with little immunity and gut colonization by competing bacteria.

In Alabama, the majority of growers clean out litter from their houses once a year in the spring. This system provides a yearly boost in performance when microbe numbers are reduced and sub-clinical infection is at a minimum. Growers report an improvement in settlement ranking associated with new litter, and integrators expect an improvement of three to four points in feed conversion and 1.5 points improvement in condemnations in the plant. In deciding when to clean out litter, the short-term benefits in live performance seen with cleanout must be weighed against the costs and labor involved in frequent cleanout, the ability of the grower to obtain sufficient bedding materials at a reasonable price and the local market for litter as a fertilizer source. Currently, a truckload of pine shavings costs around $700. This would place the cost of replacing shavings in a house at $700-$1,400. The cost of having the litter removed would be added to this in figuring the cost of cleaning out regularly. This must be balanced against the increased costs of ventilation and litter treatment necessary with built-up litter.

Managing litter between cleanouts

If conditions are such that regular cleanouts are difficult to accomplish for any reason, growers must use litter management techniques to keep built-up litter from being an economic drain on their operation. During the growout, ventilation, heating (when necessary) and water quality must be managed to keep litter dry and minimize ammonia and microbe levels. If house management is substandard during growout, microbe levels, particularly bacteria and coccidia (viruses actually like dry conditions) will increase to the point that reducing these levels between flocks becomes more difficult. For this reason, built-up litter systems require tighter house management to work properly. This concept becomes particularly evident if growers in an area must reuse litter for several years as is common in some broiler growing regions. Good house management, combined with a number of techniques (decaking, windrow composting, litter treatments, tilling) will allow growers to make the most of built-up litter if litter reuse for more than one year is needed.

Downtime must also be considered if litter is reused. Resting litter between flocks allows microbe levels to decrease as the litter cools and dries out. An economic balance must be reached between company and grower income and the biology of house environment. A minimum of 10 days downtime will allow litter to cool and dry sufficiently to reduce microbe numbers. If possible, 14 days downtime will reduce the disease threat even more. It must be remembered, however, that spore-forming bacteria will not be reduced with downtime. For this reason, spore-formers like clostridia (associated with gangrenous dermatitis and necrotic enteritis) may build up over time. Cleanout is the best option if conditions associated with spore-forming bacteria become a problem.

In-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. Growers frequently use a box blade to create windrows, although several companies make compost turning equipment that works wonderfully to make windrows in a poultry house. Creating windrows will require several hours of work per house. Respreading litter after composting will take a similar amount of time. Cake may be left in to provide enough moisture for compost bacteria to proliferate. If litter moisture is low, the targeted bacteria will not grow and the proper composting temperature will not be obtained. Most growers will run a cruster through the house to break up the litter and incorporate air.

Research completed in the Poultry Science Department at Auburn University and at Louisiana State University (Theresia Lavergne) shows that maximum temperatures (130 F to 140 F) are reached within 24 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 three- to five-day in-house composting program between flocks is a useful way to reduce viral and bacterial pathogens and improve bird performance. High temperatures were maintained even longer in covered windrows. Covering allows all litter (including that on the outside) to compost and holds ammonia that contributes to killing microorganisms.

Using windrow composting to partially rejuvenate litter, if cleanout isn't feasible, makes sense from an economic viewpoint. Reduced levels of fragile microorganisms such as the LT virus, campylobacter and salmonella help to insure optimum bird performance and reduce human food safety concerns. Reduced loads of other harmful bacteria and viruses allow birds to use feed for growth and performance rather than for fighting off mild (and often unseen) disease challenges. Also, litter ammonia levels are reduced at the start of the next batch of birds. Although improvements in performance from in-house litter composting may not mimic total cleanout and sanitation, health and performance improvements are substantial and pay dividends for the efforts that the grower must invest.

Litter treatments

Much of the broiler industry has embraced the use of litter treatments to improve performance and health when broiler litter is reused. In general, reduction of house ammonia levels is the primary purpose for using a litter treatment, although reducing litter pH also reduces microbe viability. 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. This is important if conditions dictate the reuse of litter for extended periods.

Built-up litter systems are common throughout the broiler industry and can be used effectively with good management. Despite this, a yearly cleanout does generally show a transitory boost in performance, indicating that subclinical infections and/or ammonia emissions do reduce performance measurably.

Many factors influence how often a grower can clean out broiler house litter; including litter sale/disposal options, bedding availability and cost, perceived disease load and litter quality. Techniques such as in-house litter composting, frequent between-flock tilling and litter treatments may help growers manage built-up litter if frequent cleanout is impractical.

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Dr. Joe Hess, associate professor, poultry science, Auburn University
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