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MicroRNAs (miRNA) are a class of non-coding RNAs important in posttranscriptional regulation of target genes. Regulation requires complementarity between the target mRNA and the miRNA region responsible for their recognition and binding, also called the seed region. Previous studies have proven that expression profiles and genetic variations of miRNA genes (miR-SNP; SNP - single nucleotide polymorphism) and their target sites (miR-TS-SNPs) have an impact on phenotypic variation and disease susceptibility in human, animal models, and livestock. MicroRNA-associated polymorphisms therefore represent biomarker potential for phenotypic traits in livestock. Effects of miRNA gene polymorphisms on phenotypic traits have been studied in several animal species but much less in cattle. The aim of the present study was therefore to analyze the genetic variability in the bta-mir-2313 gene and test associations with growth and carcass traits of the Slovenian Simmental cattle breed. Additionally, validated and predicted genomic information related to the miRNA gene bta-mir-2313 has been obtained and presented as an atlas of miRNA regulatory elements. Sanger sequencing has been used for biomarker development and genotyping of 145 animals of Slovenian dual-purpose Simmental cattle. Out of nine known polymorphisms located within pre-miRNA regions, one mature miRNA seed SNP was polymorphic in the Slovenian Simmental cattle breed. An additional three polymorphisms were identified within the flanking pri-miRNA regions. There was no significant effect of polymorphisms on 18 tested fattening and carcass traits; however, validated polymorphisms could now be tested in association with other traits in other cattle populations. The microRNA gene bta-mir-2313 warrants further genetic and functional analyses since it overlaps with a large number of quantitative trait loci (QTL), has over 3100 predicted targets and highly polymorphic mature seed regions, and is located within protein-coding gene GRAMD1B, previously associated with production traits in cattle. Mature miRNA seed SNPs present important genomic loci for functional studies because they could affect the gain/loss of downstream targets and should be systematically studied in cattle. [ABSTRACT FROM AUTHOR]

To study the genetic relationship between the lifetime milk production (LMP), first lactation milk yield (MY305), and length of productive life (PL) in the Slovenian Brown cattle population, first lactation records from 14,389 cows and lifetime performance records (LMP and PL) from 12,416 cows were used. Records of LMP and PL were normalised using the square root transformation of the raw values. The fixed effect of the first calving year-season oscillated between different seasons within a year for all the traits. These changes followed a seasonal pattern in MY305, where cows with first calving in colder seasons of a year had the highest MY305 and cows with first calving in the warmer seasons of a year had the lowest. The estimated heritability was 0.12±0.017 for LMP, 0.09±0.015 for PL, and 0.15±0.001 for MY305. Genetic correlation between LMP and PL was very strong (0.96±0.008), while it was moderate (0.48±0.067) between LMP and MY305 and weak between PL and MY305 (0.23±0.085). The common herd environment correlation between PL and MY305 was moderate and negative (-0.41±0.052), whereas it was weak and positive between the LMP and MY305 (0.26±0.057) and strong and positive between LMP and PL (0.74±0.025). For the last 40 years, a positive genetic trend was observed for LMP and MY305, while the genetic trend for PL remained stable. [ABSTRACT FROM AUTHOR]