A linkage disequilibrium study in layers and broiler commercial chicken populations

Knowledge of the linkage disequilibrium (LD) pattern is useful in animal genetic studies as it underlies mapping studies and genomic selection. Recently, the availability of the high density 600K Affymetrix® Axiom® HD SNP genotyping array allows to asses a higher resolution of the LD structure in chicken genome. In this study, we analysed genotypes of 1541 animals from layers and broiler commercial populations to characterize their LD pattern. LD was measured by the average r2 value at a given physical distance between SNP. LD extends over a larger region for layers line than for broiler line. Most differences between lines appeared at small interval distance (< 0.5Mb). LD extent and decay differed considerably between chromosome categories. Average r2 values were higher for Z chromosome than for macro, intermediates and microchromosomes. The extent of useful LD observed for autosomal chromosomes is at least tenfold longer for layers line than for broiler. Finally, this study shed light on high LD for the Z chromosome. The differences in LD pattern observed between chromosomes and chicken lines should be taken into account to define an economically efficient genotyping strategy.