Health traits in dairy cattle have crucial meaning to produce high quality milk. Despite of fertility problems and metabolic disorders in cows, the mastitis has a bigger economic losses influence to include it as selection criteria in cattle breeding. Somatic cell count (SCC) in that case are the good predictor for monitoring udder health cows under whole population level or separate herd. The aim of our study was to assess genetic and genomic components for SCC and their scores (SCS) using experimental dataset by seven herds with the subsequent QTL identification. For six-month observation the 5824 cows with 19786 test-day records were included into analysis. Then EBVs by offspring assessing of 139 genotyped Holstein sires were calculated trough TD Model (BLUPF90) and then it adopted as pseudo-phenotypes for GWAS. After quality control using Plink 1.90, we used ≈39K SNP (Illumina 50K). The average values for SCC and SCS were 351±7 thousands cells/ml and 2.86±0.02 score respectively. Heritability coefficients revealed low genetic variation for SCC – 0.119 and moderate for SCS – 0.211. Daily yield for cows with SCC >1000×103 cells/ml was low by -4.0 kg milk to compare individuals with SCC < 100×103 cells/ml. At the same time lactose content and freezing point were decreasing by 4.93 to 4.69% and -0.635 to -0.618°C. By Cattle QTLdb we identified some causal genes for SCC on BTA3 (ROR1), BTA9 (EZR), BTA13 (OSBPL2,DNAJC5,ZBTB46,MTG2), BTA14 (KHDRBS3) and BTA22 (RBMS3). But more relevant GWAS calls were found for SCS by BTA14 (KCNB2, ZFAT) as QTL associated to the milking speed that has unfavorable genetic correlation with clinical mastitis or SCS. Thereby, genes detected under experimental study, are the valuable and informative markers to implementation genomic selection methods for cattle health in creating Russian bulls’ reference population. The study was funded by RFBR within project No. 20-316-90050

Milk fatty acids (FA) derived from infrared spectra are a new type of traits that allow fast and predictability use their in dairy breeding and herd cattle management. The Holstein animals feature are the high milk yield, but milk composition traits can be different according to population or country origin. The purpose of our study was to find out genetic variation for milk FA and detect QTLs associated with Holstein sires’ EBV in Russian cattle population. For this analysis, we used an experimental dataset for 36982 milk test records from 14 breeding herds in the Moscow region. Individual milk samples per animal analyzed routinely by MilkoScan7 for different FA types: C14:0, C16:0, C18:0, C18:1, saturated, mono- and polyunsaturated, short-, medium- and long-chain. Total number of bulls consisted 778 individuals including 222 animals with genotypes (39051 SNP, Illumina 50K). For calculating EBV by Sire Model, we applied BLUPF90. Plink 1.90 performed quality check control and GWAS procedure. Heritability coefficients were 0.071–0.155 for C14:0-C18:0 levels, 0.196 for C18:1, 0.083 for SFA, 0.018 for PUFA, 0.176 for MUFA, 0.114–0.155 for SCFA-LCFA levels. GWAS revealed most significant (P < 0.001-0.00001) frequently QTLs associated with FA content that were cited in articles previously for BTA5 (CHST11,C18:1), BTA6 (KCNIP4,C18:1; PPRAGC1A,C18:0), BTA11 (NRXN1,LPIN1,C18:1; NBAS,C18:0), BTA26 (PCDH15,PUFA; PRKG1,C18:1). These genes were responsible for synthesis milk fat, fertility, udder conformation traits, lauric, myristic, myristoleic, palmatoleic, oleic and other types of FA. In addition, we identified several QTLs for C14:0, C16:0, SFA, MUFA, SCFA, LCFA on BTA1 (137.32 Mb), BTA10 (5.50 Mb, 9.79 Mb), BTA14 (44.35 Mb), BTA19 (17.57–17.89 Mb) and BTA22 (14.02–14.06 Mb, 20.29–20.45 Mb). Our results are the first steps toward to understanding genetic and genomic mechanisms for using FA in selection processes to improve milk quality for Holstein cattle in Russia. The study was funded by RSF (project No. 21-76-20046)

The results of the evaluation of genomic inbreeding of stud bulls of Black-and-White and Holstein breeds of the Central region of Russia are presented. The studies were carried out by detecting long homozygous fragments in the animal genome – runs of homozygosity (ROH), compared to the traditional approach of determining inbreeding by pedigree. ROH analysis was performed using the Illumina Bovine SNP50K v2 BeadChip biochip with the density of 54609 SNP in the population of stud bulls of Black-and-White and Holstein breeds (n = 100) in Moscow and Leningrad regions. The largest number and total length of ROH in the studied population were found on chromosomes 3, 6, 9, 10, 20, and 24, with an average length of 10.34; 9.15; 10.33; 12.37, and 9.05 Mb, respectively. The number of ROH segments varied from 5 to 34, with an average of 19.1. The average ROH size was 8539 ± 161 kb with the total number of nucleotide mutations of 136.2 ± 2.5 SNP and coverage density of 62.2 kb. It was found that the larger the inbreeding value by pedigree, the higher the frequency of occurrence of homozygous segments (on average from 15.5 to 25.7, respectively, with the inbreeding value from 0 to 8.5%). The total length of the fragments and the average value of ROH tend to increase depending on the inbreeding level (271.3 Mb and 10862 kb at the inbreeding value of 5.0% and higher). The highest repeatability with the inbreeding coeffi cient was obtained for the sum of homozygous genome patterns and diallelic markers, 0.517 and 0.475, respectively. Monitoring the level of homozygosity on the basis of genomic information most accurately refl ects the true level of inbreeding, and allows more effi cient monitoring of the breeding process in animal populations.

The article presents results of milk productivity analysis and calculation of the breeding value of cows (EBV) of different levels of productivity, using the BLUP ANIMAL MODEL methodology. The studies were carried out on Simmental cows from 14 regions of Russia, the total number was 61816 heads. The levels of development of the main parameters of milk productivity were assessed and a forecast of the breeding value of cows according to a number of parameters was obtained. It was found that productivity of Simmental cows born after 2005 is significantly higher: by +617 kg of milk (P≤0.001) and + 0.06% of protein in milk (P≤0.001), with a decrease of -0.02% of fat (P≤0.001), a service period of -4 days (P≤0.001) and the number of milking days by -20 (P≤0.001) in comparison with cows born earlier. Animals born after 2005 have higher EBV by mass fraction of milk fat with an average productivity of 5000 to 7000 kg of milk, where they have positive values in the range of + 0.0021 ... + 0.0041%, in comparison with cows born before 2005 years, which have negative values -0.0107 ... -0.0020%. As for EBV by mass fraction of milk protein of cows born after 2005, they had negative values in the range of -0.0037 ... -0.0008%, nevertheless, their values were much higher than the values of cows born earlier 2005 (values of -0.0057 ... -0.0028%). Sufficiently high correlation coefficients were obtained, r = 0.568 between phenotypic parameters of milk yield and its estimates, and r = 0.450 between parameters of the mass fraction of fat and its estimates.

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