Investigação do controle genético de variáveis relacionadas com a saúde do casco e conformação na raça holandesa

Abstract

The main objectives of this study were to perform genome-wide association studies using imputed high-density genetic markers data from North American Holstein cattle, for eight hoof-related traits: digital dermatitis (DD), sole ulcer (US), sole hemorrhage (HS), white line lesion (DLB), heel horn erosion (ET), interdigital dermatitis (DI), interdigital hyperplasia (HI) toe ulcer (UP) and a hoof health index (ISC), for thirteen body conformation traits: body condition score (BCS), body depth (PC), bone quality (QO), chest width (LP), dairy capacity (CL), foot angle (ANG), front legs view (VPD), heel depth (PT), height at front end (AF), locomotion (LOC), rear legs rear view (VTPT), rear legs side view (VLPT) and stature (ST) and a composite feet and leg score (IPP). De- regressed estimated breeding values (dEBVs) from 39,135 Holstein animals were used as pseudo-phenotypes for the association analyses. The molecular marker quality control, genotype phasing, and genotype imputation were performed using the PLINK, Eagle, and Minimac4 software, respectively. A mixed linear model was used to estimate SNP effects in the GCTA package. The functional genomic analyses were performed using the GALLO R package and the DAVID platform. A total of 22 significant SNPs were found for DD, 34 for ET, 14 for DI, 22 for HI, 28 for HS, 33 for US, 24 for UP, 43 for DLB, 15 for ISC, 20 for ECC, 60 for PC , 13 for QO, 17 for LP, 27 for CL, 13 for IPP, 8 for ANG, 7 for VPD, 19 for PT, 4 for AF, 10 for LOC, 13 for VTPT, 15 for VLPT and 7 for ST. The significant markers were located across the whole genome, except on the chromosome BTA27. Moreover, these genomic regions overlapped with various previously reported quantitative trait loci (QTL) for exterior, health, meat and carcass, milk, production, and reproduction traits. Enrichment analyzes identified 71 significant gene ontology terms. These findings indicated that hoof health and body conformation traits are highly polygenic and influenced by a wide range of biological processes.