Genome-wide association studies for immunoglobulin concentrations in colostrum and serum in Chinese Holstein

The early death and health problems of calves caused substantial economic losses in the dairy industry. As the immune system of neonates has not been fully developed, the absorption of maternal immunoglobulin (Ig) from colostrum is essential in protecting newborn calves against common disease organisms in their early life. The overwhelming majority of Ig in bovine whey is transported from the serum. Therefore, Ig concentration in the colostrum and serum of dairy cows are critical traits when estimating the potential disease resistance of its offspring.

Colostrum, blood, and hair follicle samples were collected from 588 Chinese Holstein cows within 24 h after calving. The concentration of total IgG, IgG1, IgG2, IgA and IgM in both colostrum and serum were detected via ELISA methods. With GCTA software, genome-wide association studies (GWASs) were performed with 91,620 SNPs genotyped by GeneSeek 150 K (140,668 SNPs) chips. As a result, 1, 5, 1 and 29 significant SNPs were detected associated with the concentrations of colostrum IgG1, IgG2, IgA IgM, and serum IgG2 at the genome-wide level (P < 3.08E-6); 11, 2, 13, 2, 12, 8, 2, 27, 1 and 4 SNPs were found significantly associated with total IgG, IgG1, IgG2, IgA and IgM in colostrum and serum at the suggestive level (P < 6.15E-5). Such SNPs located in or proximate to (±1 Mb) 423 genes, which were functionally implicated in biological processes and pathways, such as immune response, B cell activation, inflammatory response and NF-kappaB signaling pathways. By combining the biological functions and the known QTL data for immune traits in bovine, 14 promising candidate functional genes were identified for immunoglobulin concentrations in colostrum and serum in dairy cattle, they were FGFR4, FGFR2, NCF1, IKBKG, SORBS3, IGHV1S18, KIT, PTGS2, BAX, GRB2, TAOK1, ICAM1, TGFB1 and RAC3.

In this study, we identified 14 candidate genes related to concentrations of immunoglobulins in colostrum and serum in dairy cattle by performing GWASs. Our findings provide a groundwork for unraveling the key genes and causal mutations affecting immunoglobulin concentrations in colostrum and important information for genetic improvement of such traits in dairy cattle.