Technical note: Development and application of KASP assays for rapid screening of 8 genetic defects in Holstein...

Specific DNA mutations underlying several genetic defects associated with embryo loss or reduced calf survivability have been identified in dairy cattle, and a convenient and cost-effective platform is required for their routine screening. We developed Kompetitive allele-specific PCR (KASP) assays for discrimination of the wild-type alleles from the associated defective alleles at each of 8 common genetic defects in Holstein cattle, involving 5 SNP [HH1, HH3, HH4, bovine leukocyte adhesion deficiency (BLAD), and complex vertebral malformation (CVM)] and 3 insertion or deletion mutations [HH5, haplotype for cholesterol deficiency (HCD), and brachyspina (BS)]. A total of 390 cows from a Chinese Holstein herd were genotyped and the carriers identified at 7 of these 8 loci (except HH4), with the highest carrier frequencies found for CVM (10.5%) and HH1 (10.0%), followed by HH3 (2.6%), BS (2.1%), HCD (1.3%), HH5 (0.8%), and BLAD (0.5%). Surprisingly, 102 cows (26.2%) carried at least 1 of the 7 defective alleles. Our results demonstrate that these KASP assays are simple, rapid, and reliable for the detection of multiple genetic defects. The high carrier frequency of these genetic defects indicates an urgent need for routine molecular testing to eliminate the deleterious alleles from Chinese Holstein cattle.