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The main objective of the research is to assess the costs and other consequences of potential measures to control pathogens associated with all stages of livestock manure management. Pathogen control measures in place or under consideration in the UK and other countries will be reviewed, and their pathogen reduction potential assessed. The possible effects of implementing these measures will be determined for different livestock production systems (ie. dairy, beef, pigs, poultry, sheep and organic), for both liquid and solid manures, throughout the whole manure management continuum. <P>
The range of effects considered will include: implications of changes to manure management systems, changes in soil fertility and cropping patterns, knock-on effects for other sectors, environmental impacts, including interactions with other government policies on the environment (e.g. NVZs and IPPC). For each pathogen control measure and livestock production system combination, the costs to the farming industry will be estimated, and the practicality and applicability of implementing the measurements assessed.<P>
The results will be presented as a ranking matrix taking into account their cost-effectiveness, practicality, applicability and environmental impact. Gaps in knowledge and priorities for further research will also be identified. <P>
Results of the research will provide scientific underpinning to DEFRA policies that promote the recycling of livestock manures to agricultural land as the most economic, practical and environmentally beneficial management option in most cases, whilst protecting public health in relation to food and to animal disease transmission to humans.
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Pathogen control measures in place or under consideration in the UK and other countries were reviewed. Measures identified included those associated with diet and dietary additives, minimum storage periods (typically 90 days) for slurry and solid manure, avoidance of recontamination of stored manures, slurry treatment, solid manure composting, spreading methods, minimum harvest intervals, minimum grazing intervals and general good practice. The pathogen reduction potential of selected measures was assessed by reference to existing literature and results from ongoing FSA-funded work (project BO 5003). The likely practical effects of implementing the pathogen control measures identified were then assessed by specialists for different farming systems (i.e. dairy, beef, pigs, poultry, sheep, organic and field vegetables/salad/fruit crops), for both liquid and solid manures.
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The costs of implementing slurry or solid manure storage or treatment measures were assessed on a livestock industry basis for England and Wales. Estimated capital costs of providing slurry or dirty water storage on all farms for 90 days were extremely high, particularly in the dairy sector. Capital costs of providing additional storage for solid manures in concrete-based stores were also extremely high, but were minimal if field heaps were used. Typical costs per m3 or tonne of manure were also calculated for all storage and treatment options. Using data on additional manure quantities stored, the potential increase or decrease in ammonia and greenhouse gas emissions, and nitrate leaching losses (in ktonnes) due to adoption of each measure was calculated, and compared with current estimates or inventories.
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Approaches to constructing a matrix to give an overall ranking of different measures were developed. The matrix summarises the pathogen reduction potential, cost, practicality, estimated changes in emissions to air (ammonia, nitrous oxide and methane) and water (nitrate), and effects on soil fertility of each pathogen control measure.
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Provisional conclusions indicate that solid manures offer the best opportunity for pathogen control via extended storage. The costs of providing extended slurry storage facilities on all farms would be extremely high. Operation of a two-store slurry system to provide batch storage would present considerable logistical challenges, in order to achieve the required storage periods and match this to land spreading opportunities. The treatment of slurry offers only limited scope, because of high capital or running costs, or safety issues.
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A provisional list of future research topics has been drawn up. These include the effect of feeding regimes on pathogen shedding, development of low-cost treatment methods for slurries, effect of location within solid manure heaps on pathogen die-off, the effects of slurry spreading technique (i.e. broadcast or band spread/shallow injection) or soil incorporation on pathogen die-off, better quantification of pathogen die-off from land applied manures and from excreta deposited directly in the field during grazing.
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This project will provide a detailed assessment of interactions between pathogen control measures, manure management practices and emissions to air and water. This will have benefits to DEFRA in implementing policies to control nutrient pollution from agriculture and to the agricultural industry, by helping to provide an integrated set of recommendations on sustainable manure management practices. <P>