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Selective breeding on PrP genotype in the UK sheep flock:evaluting the consequences and deriving optimal strategies - SE0236

There is concern over the TSE status of the UK sheep flock, particularly since it is known from experimental studies that BSE can infect sheep. The National Scrapie Plan (NSP) aims to reduce and eventually eradicate small ruminant (SR)-TSEs from the national sheep flock. A key element of the NSP is a breeding programme based on PrP genotype, which determines the resistance of sheep to scrapie. However, a focus on scrapie genotype alone is risky, if favoured alleles are antagonistic to other economically important traits or sufficiently rare that their selection increases inbreeding and reduces genetic variability. Selection for scrapie resistance thus must fit within an overall genetic improvement scheme but the optimal way of achieving this is unknown.

The effectiveness of the breeding component of the NSP will be determined by farmer compliance which, in turn, depends upon confidence that PrP-based selection will have no adverse consequence upon sheep performance, health or adaptation. Although no such relationships have been detected to date, the lack of an overall research strategy to assess possible relationships between PrP genotype and other traits was recently identified as an outstanding gap by the SEAC NSP Working Group.

The overall objectives of this research programme are (1) to collect and analyse the information necessary to critically evaluate the impact of widespread selection on PrP genotype in the UK sheep population, and (2) to devise optimal breeding strategies for scrapie resistance in the context of an overall genetic improvement programme. The programme will (i) investigate relationships between PrP genotype and traits of economic importance to the farmer, and monitor the continued impact of the NSP on such traits, (ii) estimate PrP allele frequencies in selected data sets, particularly for rare breeds, and (iii) identify optimal breeding designs for scrapie resistance with restrictions on the loss of genetic variability.

The programme of research will be implemented at the national level, covering all major sectors of the sheep industry. Data from major breeds within the terminal-sire, longwool and hill sectors will be collected and analysed as will data from a sample of rare and traditional breeds. Breeding strategies will be advocated that are tailored to the nature of each breed and sector which is a function of the traits of importance, the population sizes and the PrP allele frequencies. Particular emphasis will be placed upon the effective dissemination of results to all major stakeholders in the UK sheep industry, and the results of the programme will address concerns voiced by sectors of the sheep industry regarding the NSP. Participants include most of the Institutes in Great Britain with major programmes in sheep genetics research and extension. This will ensure that the research is tightly focussed on the needs of end users (i.e. government departments;NSP managers;breed societies;sire reference schemes;the Rare Breeds Survival Trust-RBST; The Sheep Trust and the veterinary profession), and that the research results are taken up speedily and effectively.

Net beneficiaries will include both the public, as there will be less potential or perceived risk associated with sheep-meat products, and the industry itself, as greater public confidence should lead to enhanced sustainability.The project is highly relevant to Defra`s aims, especially to the sustainable use of natural resources;to economic prosperity through sustainable farming and to the creation of thriving economies and communities in rural areas.It is particularly relevant to Defra`s objectives 1 (to conserve and enhance biodiversity), 2 (to promote sustainable rural areas), 3 (to promote a sustainable, competitive and safe food supply chain which meets consumers requirements), 5 (to promote sustainable, diverse, modern and adaptable farming), 6 (to sustain management and prudent use of natural resources) and 7 (to protect the public`s interest in relation to health and diseases,which can be transmitted through food, and to ensure high standards of animal health and welfare).

The proposed project addresses issues of profitability, sustainability, diversity and health,important areas highlighted in the recent report of the Policy Commission on the Future of Food and Farming.
Project Documents
• Final Report : Final report   (386k)
Time-Scale and Cost
From: 2004

To: 2007

Cost: £1,869,155
Contractor / Funded Organisations
University - Wales, Aberystwth, Veterinary Laboratories Agency, Roslin Institute, Edinburgh (BBSRC), Meat and Livestock Commission, University - Edinburgh, SAC Commercial Ltd
Animal Health              
Plants and Animals              
Fields of Study
Animal Health