Embryonic lethality due to recessive alleles is a major concern in livestock breeding programs. The Online Mendelian Inheritance in Animal (OMIA) is a database of reported recessive mutations in livestock that helps breeders to manage the segregation of these mutations in their population. Recessive alleles are lethal in the offspring of two carrier parents; therefore, identifying and eliminating carrier animals are critical for maintaining the breed. Hanwoo cattle is native to the Korean peninsula and is of great economic importance to Korea. Due to geographical constraints and the controlled breeding program with very few proven bulls, if not monitored periodically, the threat of segregation of recessive lethal alleles in the population remains high. Therefore, identifying potential carriers of lethal recessive alleles is critical in Hanwoo. In this regard, we genotyped 17,325 animals using bovine 50K Illumina SNP chip and also sequenced a further 311 animals which was mapped against the bovine reference genome sequence. We then used the OMIA database to identify reported recessive alleles and calculated the allele frequency of these mutations in the population to determine potential lethal alleles carried by the animals.

Carrier testing for autosomal recessive hereditary disorders in the elite sire population has great significance for the domestic animal breeding. Because the recessive allele embedded in carriers without clinical signs may be passed to the next generation and rapidly spread throughout the population. The occurrences of various autosomal recessive hereditary disorders have been reported, and several causative mutations were elucidated in cattle. However, there is no report for the hereditary disorders in Korean cattle (Hanwoo) although Hanwoo is the indigenous purebred in Korea and have been improved by the national breeding programs in the last 30 years. Here, we investigated the presence of carrier for the following hereditary disorders in the Korean proven bulls (n=78; 42 family) using DNA based analysis: Chediak–Higashi syndrome, spherocytosis, claudin-16 deficiency, factor XI deficiency. The causative genes for these diseases (lysosomal trafficking regulator, solute carrier family 4 member 1, Claudin-16 and coagulation factor XI, respectively) were analyzed by polymerase chain reaction and direct sequencing. As a results, there was no carrier individual, and all animals were normal. Although the recessive alleles for four disorders were not identified in this study, further investigation for other hereditary disorders still remains to remove deleterious factors in the genetic improvement of Korean cattle.