Towards marker assisted selection in livestock

In recent years, genomic tools have become available for most livestock spe cies and are now being used routinely to map quantitative trait loci underl ying the genetic variance for numerous economically important traits. Fine- mapping methods are beings devised to refine the initially coarse map posit ions of the quantitative trait loci to the point required for marker assist ed selection and, eventually, the positional cloning of the underlying gene s. Mapping information on QTL is beginning to be used to increase genetic r esponse by enhancing genetic variance, selection accuracy, selection intens ity and by reducing the generation interval. Optimal use of MAS will requir e the development of more robust methods for the routine genotyping of prei mplantation embryos for multiple markers. (C) Inra/Elsevier, Paris.