Milk fat is one of the key traits in dairy production influencing both the nutritional and technological value. In this master’s thesis, we investigated the genetic background of the trait milk fat yield in Brown Swiss cattle by analyzing 65 single nucleotide polymorphisms (SNPs) showing the strongest association with the trait, based on data from the Interbull InterGenomics database. Using the Ensembl database, we found that 40 SNPs were intronic, 20 intergenic, and five were not recorded in Ensembl. Most SNPs were located on chromosomes 5, 11, 14, and 19, within candidate genes such as GHR, PLEC and MGST1. Information on the genes within or near which the SNPs were located was compared with the QTLdb database, where we verified overlap with previously reported quantitative trait loci (QTLs) for milk production traits. We confirmed that 16 genes have previously been associated with milk fat yield. We also proposed new potential candidate genes, such as SHISA9, BORCS5 and PRKAG2. Some genes, including TANC2, EGFLAM and GINS4, were associated not only with the studied trait but also with other milk production traits. The analysis of interactions revealed functional connections between certain genes. The results contribute to a better understanding of the complex genetic regulation of milk composition and yield and provide a foundation for further research and potential application in genomic selection in Brown Swiss cattle.
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