A total of 285 healthy mid-lactation Holstein dairy cows (days in milk: 158 ± 32.8, parity: 2.99 ± 1.10, mean ± SD) were selected from a commercial dairy farm. DNA was extracted from whole blood according to Wizard Genomic DNA Purification Kit (https://www.promega.jp/resources/protocols/technical-manuals/0/wizard-genomic-dna-purification-kit-protocol/) and subjected to genotyping at Delta Genomics (Edmonton, AB, Canada). QuantiFluor dsDNA system (Promega, Madison, WI) was used for quantitative analysis of DNA samples, and genotyping was performed using Bovine Geneseek Genomic Profiler Low-Density 31K Beadchip (V.4, Neogen Inc, Lincoln, NE) according to the Illumina Infinium Ultra manual (Illumina, San Diego, CA). Illumina HiScan was used to scan the chip.