The dairy sheep industry in Western European countries is mainly based on the production of high quality PDO cheeses. Thus dairy sheep selection has been oriented towards milk yield and milk composition (protein and fat content) to maintain competitiveness of this production. Due to the evolution of the EU agricultural policy and consumers demand, more attention has been now given to traits related to the reduction of production costs (milkability, functional traits, longevity), health (resistance to mastitis or parasitic diseases) and safety food (milk content in fatty acids related to human health). In most situations, only a part of these new traits is extensively recorded in the nucleus flocks of the purebred breeding schemes (Barillet, 1997; Rupp et al., 2002 ; Sanna et al., 2002). Therefore research combining classical quantitative approach and QTL detection is needed, either on-farm by implementing experimental recording schemes, or in experimental flock especially for traits difficult and costly to record. Crosses between breeds to produce F2 or backcross experimental population allow to exploit linkage disequilibrium for genes differing between breeds and to detect genome regions controlling the traits of interest. In the light of this, an experimental Sarda x Lacaune backcross resource population was produced in 1999 by INRA (France) and IZCS (Italy) in order to detect QTL both on milk production and on traits difficult to measure through a whole genome scan. The Sarda and the Lacaune are the two most numerous French and Italian dairy sheep breeds, and they differ for a lot of traits as body size, growth rate, wool characteristics, prolificacy, milk yield level and milkability. Their dairy selective history is also very different (Barillet et al., 2001 ; Carta et al., 2002). The purpose of this paper is to give an overview of the Sarda x Lacaune project and to illustrate it by summarizing the results of first QTL analysis for milk production traits in first lactation on sheep chromosome three (OAR 3).
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 2002. Session 1, , 1.4, 2002
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