Estudos de associação genômica ampla para características de qualidade do leite em bovinos da raça holandesa do Brasil

Abstract

With the accelerated development of the industry, increasingly aiming for quality and performance, it was necessary to seek innovative tools so that herds can keep up with market demands with profitability and well-being. With genome-wide association studies (GWAS) there are reports of many molecular markers that contribute to milk production, and milk fat and protein characteristics, in the Holstein Breed. Over the years, several GWAS studies have identified genes relevant to milk and solid production in different Holstein populations. However, there is still not much information about the genome of these animals in Brazil, where they are kept under breeding, management and climate conditions that are different from other places where genomic studies are already more advanced. Therefore, in this study, important genomic regions were found for the percentage of fat and protein, as well as the production of protein fat in kilos, in Holstein cattle raised in Brazil. In this study, milk production data was analyzed in 2,339 Holstein cows in four Brazilian states between 2021 and 2022, with 84,411 markers after quality control, using the GGP Bovine 100k SNP Chip. The ssGWAS approach was applied with the BLUPF90 family of programs, followed by the exploration of genomic regions with significant SNPs (P-value <5x10- 8) and identification of associated genes, complemented by enrichment analyzes and gene networks using DAVID tools and STRING. The CPSF1, CYHR1, DGAT1, SLC52A2 and TSNARE1 genes were found in all analyzed traits. And the genes that had the highest peak in the Manhattan Plot graphs were the SLC52A2 and DGAT1 genes. For protein production in kilos, 17 chromosomes were found in 30 different genes, while for PTA fat production in kilos, 27 genes were found in 16 chromosomes. Regarding the protein percentage, 12 genes were found on 3 chromosomes and for fat percentage, 48 genes were found on 23 chromosomes. In the analysis of functional parameters, it was observed that the genes CSN1S1, CSN2, PLEC, SVEP1, MAML3, MRTFA and MRTFB play a predominant role in biological processes related to the kilo protein characteristic. With regard to the protein characteristic in percentage, the genes EPPK1, PLEC, VPS28, ADGRB1, CSN1S1, CSN2, CSN3, MAPK15, TRAPPC9, GHR, HSTN, CPSF1, ZC3H3 and SLC4A4 were identified as most relevant. For fat production in kilos, 35 genes were found, the most evident being the PLEC gene and of the 42 genes for fat percentage, the genes with the highest incidence were AGO2 and AGO3. These genes may be related in the functions of biological processes, related functions of the cellular component and molecular function. Direct or indirect functions for milk production have not yet been established in the literature for the genes AGO2, AGO3, ARHGAP39, C25H16ORF82, CDH3, CMYA5, DENND3, EEF1D, ENSBTAG00000025756, ENSBTAG00000038214, ENSBTAG00000048091, ENSBTAG00000 051599, ENSBTAG00000053188, ENSBTAG00000054671, ENSBTAG00000055067, EXOC3, FBXO43 , GLT6D1, GNAI3, GPAA1, GRHL2, GUCA1A, IQANK1, IVNS1APB, KCNA4, KIAA0753, KMT2E, LRRC1, MAF1, MAPK15, MLIP, MRTFB, NADSYN, NCALD, OPCML, OR2D37, OSCP1, OSR2, PIK3C2G, PTK2, PTPN14, RAB2A , RAP1GAP2, RCN3, RERG, RGMA, RNF1144B, RNF19A, RTRAF, SEMA3A, SH2D4B, SPAG1, SPIN1, STK40, TNRC6B, UBXN2A, ZBTB46 and ZNF691. Therefore, these genes can contribute to the genetic improvement of the Brazilian Holstein breed, being expressed in dairy herds raised in tropical and subtropical environments. This study played an important role in investigating the genetic composition of Holstein dairy cattle raised in Brazilian environmental conditions. This research aimed to obtain greater knowledge of favorable genetic variants that can contribute to increasing national dairy productivity.