Rapid Communication: Genome-wide association analyses identify loci associated with colostrum production in Jersey cattle1

Consumption of an adequate volume of high-quality colostrum soon after birth is critical for a calf's health. Few studies have focused on the genetics associated with colostrum production, even though several dairy herds in the United States have reported incidents of low to no colostrum production during the fall and winter seasons. The objectives of this study were to identify loci associated with quantity and quality of colostrum production in a herd of Jersey cattle (n = 345) and to identify potential positional candidate genes and/or transcription factor binding site motifs located near associated loci. Cattle that freshened between the months of October and December of 2016 at a single dairy were enrolled in the study and produced on average 3.03 kg of colostrum at their first milking. This study included 112 cattle genotyped with the GeneSeek GGP50k BeadChip and another 233 cattle previously genotyped with various other arrays. The 233 cattle genotyped at lower densities were imputed to the GGP50k BeadChip density using BEAGLE 4.1.1, and 2 genome-wide association analyses (GWAA) were conducted using an additive efficient mixed-model association expedited method with a genomic relationship matrix (EMMAX-GRM). The first GWAA investigated loci associated with colostrum quantity and identified 7 loci: 6 that were moderately associated (5 × 10-07 > P < 1 × 10-05) and 1 that was strongly associated (P < 5 × 10-07). The second GWAA investigated colostrum quality and identified 1 moderately (5 × 10-07 > P < 1 × 10-05) associated locus. Five loci harbored positional candidate genes which had functional relevance to colostrum production, and 1 locus located on BTA10 contained a transcription factor binding site motif for TFAP2A which has previously been linked to mammary gland development. Pseudoheritability estimates were moderate for colostrum quality (0.19 ± 0.06) and high for colostrum quantity (0.76 ± 0.11), suggesting that genomic selection for these traits would be possible. Diminished colostrum quantity or quality can have a significant impact on herd health and herd economics. The identification of loci, positional candidate genes, and transcription factor binding site motifs associated with colostrum production could be used in genomic selection to allow producers to select for cattle with good colostrum production, improving calf health, and reducing economic losses to the herd.