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Detection, Quantification and Modification of Bacterial Populations Associated with Broiler Poultry Litter


<OL> <LI> Develop a novel quantitative PCR method to determine the amount and type of bacteria present in poultry litter. This PCR will be based on the highly conserved 16s rRNA regions of the bacteria's chromosome. It has been shown previously that bacterial numbers and types can be detected in complex microbial communities with little loss of resolution (Lu, et al., 2003). Using this technique it will be possible to measure the bacterial populations in untreated versus any one of the various litter treatment techniques described above. <LI>The initial phase of the study will be performed at the Auburn University Poultry Research Farm (AUPRF). At the AUPRF, unsoiled bedding as well as litter that has been exposed to multiple flocks will be tested both before and after chemical, biological and physical treatment. From the results generated in these studies a baseline level of what to expect in the field will be obtained. The eventual goal of this project is to obtain samples and flock history records from commercial poultry farms. These data will be analyzed and any significant trend noted. It is expected that there will be variations from the AUPRF baseline. However there should be general trends as to what makes up good litter quality that minimizes disease and ammonia production. <LI> Explore novel techniques in reducing antagonistic bacteria and ammonia production. From the results obtained in objective 2, it is believed that a better litter amendment can be developed. This will be performed by determining what microbes are present in litter associated with poultry flocks that had superior performance. Performance will be determined by where the flocks ranked when it went to market as well as to the health status of the flock. With this microbial profile it should be possible to develop a bacterial based litter amendment. Additionally, it will be possible to determine which, if any of the current litter amendments lead to this profile. Any developed litter amendment will be tested in grow out trials to determine the reproducibility of the results over an extended period of time.

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NON-TECHNICAL SUMMARY: Proper litter management is important for good bird health as well as their ability to resist colonization by foodborne pathogens. As the cost of bedding and the difficulty in disposal increased, the practice of keeping litter in the house longer has gone up. This has lead to an increase in ammonia exposure to newly placed chicks as well as an increased chance of exposure to pathogens from the preceding flock. These issues are controlled by the addition of litter amendments or by physically manipulating the litter and often times a combination of both. Litter amendments can be broken down into one of two categories, those being either chemical or biological. Among the chemical amendments there are two main classes, one being the acidifiers and the other the alkaline. The acidifiers work by lowering the litter's pH. This lowering of the pH causes a reduction in ammonia production as well as a decrease in microbial numbers. The alkaline amendments work by increasing litter pH, this results in a decrease in microbial numbers. However it doesn't decrease ammonia production. Biological litter amendments are more difficult to classify; essentially they are either bacterial, enzymatic, or plant based. There are several bacterial amendments and although they generally have different bacterial mixtures, they all have the same general mode of action. They, like the chemical amendments, work by either lowering or raising the pH of the litter and by acting as a competitive exclusion agent within the litter. The second category of biological amendment mentioned is the enzymes. These work by either preventing the nitrifying bacteria from forming ammonia or by causing an increase in ammonia production from this same category of bacteria. The third group of biological litter amendments are the plant based ones. These amendments work similarly to the enzyme based ones in that they inhibit the production of ammonia by means of enzymes present in the plant. These particular amendments can be either directly added to the litter or fed to the birds. The objective of physically manipulating the litter is to dry the litter. By drying the litter there will be a decrease in bacterial numbers which in turn leads to less potential pathogens as well as a decrease in nitrifying bacteria. There are several different methods for accomplishing this. Essentially all of them involve mixing the litter. This action allows moisture to be removed from the litter, thus drying the litter which in turn leads to lower bacterial and ammonia levels. Although the mentioned methodologies have been used for some time, relatively little is known as to how they affect the litter's microbial profile. Generally it is thought that they are manipulating this microbial profile in a positive way; however this has yet to be determined. Perhaps from the above mentioned, a combination of, or from as yet unknown methodology an ideal litter treatment program can be developed. This program would ideally minimize the exposure newly placed chicks have to ammonia as well as to pathogens.


APPROACH: Quantitative PCR should make identification of general as well as specific bacteria relatively simple. It is believed that this technique will lend itself to a fast, easily performed identification of litter microbes. Using the developed technique, the ability to sample various litter samples should proceed rather quickly. Using this technique to determine the affect of the various litter treatments on litter microflora will help answer questions as to how these treatments are manipulating the litter microflora. As more is learned about the effects of litter treatments on the litter's microflora it is anticipated that a novel litter treatment may be devised that can lend themselves to a better litter quality. Better litter quality will lead to less stressed birds, which in turn will lead to healthier birds. Healthier birds should lead to less pathogens entering the processing plant, hence into the food chain.

Macklin, Kenneth
Auburn University
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