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Wageningen Universiteit (2008)

Sheep resources of Ethiopia : genetic diversity and breeding strategy

GebreMichael, S.G.

Titre : Sheep resources of Ethiopia : genetic diversity and breeding strategy

Auteur : GebreMichael, S.G.

Université de soutenance : Wageningen Universiteit

Grade : PhD thesis 2008

Résumé
Twenty percent of the world domestic animal breeds are classified as being “at risk” of extinction. Seventy percent of the mammalian breeds, for which no risk status data are available, are found in the developing world. This is a serious constraint to effective prioritization and planning of sustainable breed conservation measures, including sustainable breeding strategies. The objectives of this thesis were to develop improved approaches to characterization of sheep resources, and sustainable conservation-based sheep breeding strategies under smallholder traditional systems, taking Ethiopia as a case study. Analysis of microsatellite variation showed that geographic isolation is the primary cause of genetic differentiation among Ethiopian sheep breeds. However, there is a strong indication of adaptive divergence in morphological characters. Using a combination of microsatellite analysis and morphological divergence, we propose a classification of Ethiopian sheep into six breed groups and nine breeds. The objective of characterizing animal genetic resources is to facilitate decisions on prioritization in conservation of these resources. Our results show that a maximum-utility-strategy combining threat status, contributions to farmer livelihoods and to genetic diversity of livestock breeds should be adopted to prioritize them for conservation purposes. Such an approach balances the trade-offs between conserving breeds as insurance against future uncertainties and for current sustainable utilization. Selective breeding within indigenous livestock breeds is an option for conserving livestock breeds. Our results indicate that selective breeding can lead to significant genetic improvement under low-input systems and marginal environments. Assessment of farmers’ selective breeding objectives showed that adaptive traits are more important than or as important as production traits, indicating that sustainable animal breeding strategies require a broad definition of breeding objectives that emphasize maintaining adaptation to local circumstances and biodiversity, in addition to profitability. It is concluded that the most rational and sustainable way to conserve livestock genetic resources is to improve their competitiveness through sustainable breed improvement programs (i.e. conservation through use). To this end, community- or village-based selective breeding schemes with full participation of farmers appear to be the best option to start with.

Mots clés : animal genetic resources / sheep breeds / genetic diversity / animal breeding / menz / sheep farming / farming systems research / morphology / microsatellites / ethiopia / ex situ conservation

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Page publiée le 9 octobre 2008, mise à jour le 1er juin 2022