Genome-wide association study for milk production traits in a Brazilian Holstein population

Authors: DE SOUZA IUNG, LAIZA - Universidade De Sao Paulo; PETRINI, J - Universidade De Sao Paulo; RAMIREZ-DIAZ, JOHANNA - Universidade De Sao Paulo; SALVIAN, MAYARA - Universidade De Sao Paulo; ROVADOSCKI, GREGORI - Universidade De Sao Paulo; PILONETTO, F - Universidade De Sao Paulo; DAURIA, B - Universidade De Sao Paulo; MACHADO, P - Universidade De Sao Paulo; COUTINHO, L - Universidade De Sao Paulo; WIGGANS, GEORGE - Council On Dairy Cattle Breeding; MOURAO, GERSON - Universidade De Sao Paulo

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/2018
Publication Date: 6/1/2019
Citation: De Souza Iung, L.H., Petrini, J., Ramirez-Diaz, J., Salvian, M., Rovadoscki, G.A., Pilonetto, F., Dauria, B.D., Machado, P.F., Coutinho, L.L., Wiggans, G.R., Mourao, G.V. 2019. Genome-wide association study for milk production traits in a Brazilian Holstein population. Journal of Dairy Science. 102(6):5305-5314. https://doi.org/10.3168/jds.2018-14811.
DOI: https://doi.org/10.3168/jds.2018-14811

Interpretive Summary: Advances in the molecular area of selection have expanded knowledge of the genetic architecture of complex traits through genome-wide association studies. Although several past studies have been performed for traditional milk production traits, confirming those results has not always been possible. This study identified genomic regions associated with milk yield; somatic cell score; fat, protein, and lactose percentages; and fatty acid composition in a Holstein cattle population producing under tropical conditions. The MGST1 (chromosome 5), ABCG2 (chromosome 6), DGAT1 (chromosome 14), and PAEP (chromosome 11) genes were confirmed within some of the identified regions. Potential novel genes involved in tissue damage and repair of the mammary gland (COL18A1), immune response (LTTC19), glucose homeostasis (SLC37A1), synthesis of unsaturated fatty acids (LTBP1), and sugar transport (SLC37A1 and MFSD4A) were found for milk yield, somatic cell score, fat percentage, and fatty acid composition. These genomic regions can be used to design a customized marker genotyping array. Such an array can be used in genomic selection to improve milk production traits on farms that operate under similar environmental conditions.

Technical Abstract: Advances in the molecular area of selection have expanded knowledge of the genetic architecture of complex traits through genome-wide association studies (GWAS). Several GWAS have been performed so far, but confirming these results is not always possible due to several factors, including environmental conditions. Thus, our objective was to identify genomic regions associated with traditional milk production traits, including milk yield, somatic cell score, fat, protein and lactose percentages, and fatty acid composition in a Holstein cattle population producing under tropical conditions. For this, 75,228 phenotypic records from 5,981 cows and genotypic data of 56,256 SNP from 1,067 cows were used in a weighted single-step GWAS. A total of 46 windows of 10 SNP explaining more than 1% of the genetic variance across 10 Bos taurus autosomes (BTA) harbored well-known and novel genes. The MGST1 (BTA5), ABCG2 (BTA6), DGAT1 (BTA14), and PAEP (BTA11) genes were confirmed within some of the regions identified in our study. Potential novel genes involved in tissue damage and repair of the mammary gland (COL18A1), immune response (LTTC19), glucose homeostasis (SLC37A1), synthesis of unsaturated fatty acids (LTBP1), and sugar transport (SLC37A1 and MFSD4A) were found for milk yield, somatic cell score, fat percentage, and fatty acid composition. Our findings may assist genomic selection by using these regions to design a customized SNP array to improve milk production traits on farms with similar environmental conditions.