Genome-wide association study for mammary structure in Canadian Angus cows

Abstract

Functional and enduring mammary structure is pivotal for producer profitability, and animal health and welfare in beef production. Genetic evaluations for teat and udder score in Canadian Angus cattle have previously been developed. The aim of this study was to identify genomic regions associated with teat and udder structure in Canadian Angus cows thereby enhancing knowledge of the biological architecture of these traits. Thus, we performed a weighted single-step genome wide association study (WssGWAS) to identify candidate genes for teat and udder score in 1,582 Canadian Angus cows typed with the GeneSeek ® Genomic Profiler Bovine 130K SNP array. Genomically enhanced estimated breeding values (GEBVs) were converted to SNP marker effects using unequal variances for markers to calculate weights for each SNP over three iterations. At the genome wide level, we detected windows of 20 consecutive SNPs that explained more than 0.5% of the variance observed in these traits. A total of 35 and 28 windows were identified for teat and udder score, respectively, with two SNP windows in common for both traits. Using Ensembl, the SNP windows were used to search for candidate genes and quantitative trait loci (QTL). A total of 94 and 71 characterized genes were identified in the regions for teat and udder score, respectively. Of these, 7 genes were common for both traits. Gene network and enrichment analysis, using Ingenuity Pathway Analysis (IPA), signified key pathways unique to each trait. Genes of interest were associated with immune response and wound healing, adipose tissue development and morphology, and epithelial and vascular development and morphology. Genetic architecture from this GWAS confirms that teat and udder score are distinct, polygenic traits involving varying and complex biological pathways, and that genetic selection for improved teat and udder score is possible.

Genetic Background and Inbreeding Depression in Romosinuano Cattle Breed in Mexico

“…Among genes found in islands, the TLEA4 gene is crucial for the function of the mammary gland and has previously been reported in Angus cattle by Devani et al [ 60 ]. Additionally, several genes (CFAP61, RALGAPA2, INSM1, and KIZ) were located in a region associated with feed intake, conformation, weight, reproductive traits, and milk production in cattle, as demonstrated by Pitt et al [ 61 ].…”

Genome-Wide Association Study Candidate Genes on Mammary System-Related Teat-Shape Conformation Traits in Chinese Holstein Cattle

“…In this study, the heritability of mammary system-related teat traits of Holstein cattle was of a medium level ( Table 1 ). Previous studies have identified that animal differences in bovine mammary systems are genetically influenced by the heritability value (estimate range between low to medium) [ 1 , 33 ]. Wu et al, 2013, estimated the heritability of front teat placement, teat length and rear teat placement (0.18, 0.21 and 0.11, respectively) in Chinese Holstein cattle [ 34 ].…”

“…Mammary system traits play an important economic role in cattle [ 1 ]. In dairy cattle, mammary infections are a major problem.…”

“…The genetic correlation between body conformation traits such as udder depth and teat traits was studied for indicators of longevity and lifetime in Dutch dairy cattle [ 17 ]. A genome-wide association study has been approved to detect the SNP that is related to quantitative trait loci of dairy cattle [ 1 , 21 ]. In post-GWAS analyses such as gene ontology (GO), term analyses have given researchers a better understanding of the molecular mechanisms underlying conformation traits and have allowed them to identify the most likely candidate genes [ 18 , 22 ].…”

“…In beef cattle, genetic estimations and selection are improving due to traits that affect efficiency as well as animal fitness and wellbeing. The Canadian Angus Association (CAA) recently established a genetic analysis in teat and udder score for enhancing genetic selection in Canadian Angus cattle [ 1 ]. Ten candidate genes for teat- and udder-associated traits in French dairy cattle were identified [ 22 ].…”