PSXII-7 - Milk somatic cells monitoring in Russian Holstein cattle population as a base for determining genetic and genomic variability

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 -0.618⁰C. 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