Linkage Disequilibrium (LD) And Association Studies In Marchigiana Cattle Breed

This study is focussed on estimating the extension of Linkage Disequilibrium (LD) and the assessment of the existence of associations between favourable haplotypes and functional traits of economic importance (longevity, fertility,...) in Marchigiana cattle breed. Genotypic and phenotypic recorded data from Marchigiana half sibs bred in two different environments (Italy and Brazil) allow to include the GxE factor in the statistical model. Thus, it will be possible to identify favourable haplotypes suitable for different breeding systems. Three chromosomal regions were investigated in 200 half daughters (100 bred in Italy and 100 bred in Brazil). Two target regions, one on BTA7 and one on BTA10, were chosen based on the presence of previously mapped QTLs for calving ease and non return rate. The third region, on BTA25, was represented by a "neutral" region where no QTLs and genes with assessed effect on traits of interest had been identified. An Illumina customized panel containing 480 SNPs, spanning the three selected chromosomal regions, was created to genotype the animals. Analyses of allelic and haplotypic frequencies are currently undergoing and the presence of associations between specific haplotypes and the selected phenotype will be assessed by using non-parametric tests. The GxE factor will be introduced into the algorithm to estimate the environmental effect on performances in Marchigiana populations clustered according to the haplotype.