The variant red coat colour phenotype of Holstein cattle maps to BTA27.

The variant red phenotype in Holstein cattle is indistinguishable from the traditional e/e recessive red phenotype caused by a mutation in melanocortin 1 receptor, but is inherited as a dominant trait in relation to black. Co-segregation analysis in four half-sib families segregating for variant red was conducted, excluding melanocortin 1 receptor, agouti signalling protein, attractin and melatonin receptor 1A as causative genes. However, variant red co-segregated with markers in a region of BTA27 that includes beta-defensin 103 (DEFB103). Two newly identified microsatellites and 5 SNPs 5' of DEFB103 were used for linkage mapping in four segregating families (LOD = 3.26). One haplotype was inherited in VR cattle in a 6-generation pedigree.