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A selective DNA pooling approach was applied to identify QTL for conjugated linoleic acid ( CLA), vaccenic acid ( VA) and Δ9-desaturase (D9D) milk content in Italian Brown Swiss dairy cattle. Milk samples from 60 animals with higher values (after correction for environmental factors) and 60 animals with lower values for each of these traits from each of five half-sib families were pooled separately. The pools were genotyped using the Illumina Bovine SNP50 BeadChip. Sire allele frequencies were compared between high and low tails at the sire and marker level for SNPs for which the sires were heterozygous. An r procedure was implemented to perform data analysis in a selective DNA pooling design. A correction for multiple tests was applied using the proportion of false positives among all test results. BTA 19 showed the largest number of markers in association with CLA. Associations between SNPs and the VA and Δ9-desaturase traits were found on several chromosomes. A bioinformatics survey identified genes with an important role in pathways for milk fat and fatty acids metabolism within 1 Mb of SNP markers associated with fatty acids contents. [ABSTRACT FROM AUTHOR]

Previous studies have reported significant associations between haplotypes of the oxidized low-density lipoprotein (lectin-like) receptor 1 (OLR1) gene and a single nucleotide polymorphism (SNP) in its 3'-untranslated region with milk composition and health traits in different cattle populations. However, to provide a better estimation of the impact and size of the association of OLR1 with production traits, a need exists to validate its genomic association in additional cattle populations. Thus, the objective of this study was to perform association analysis of the OLR1 SNP with milk traits in the Israeli Holstein population. Estimated breeding values of milk composition traits and somatic cell score were obtained for a total of 1,211 Holstein cows, which were genotyped for a SNP in the 3'-untranslated region. Statistical analysis revealed significant association between the OLR1 SNP and protein percentage and somatic cell score. Thus, the validation of association of this SNP with milk traits in independent cattle populations suggests OLR1 as a candidate gene for further functional studies. [ABSTRACT FROM AUTHOR]