This breed of cows is called Belgian Blue. It comes from Belgium where it was engineered in the 19th century by crossing local cattle with cattle from the United Kingdom. The breed has a natural mutation of the gene responsible for accelerated muscle growth, resulting in heavyly muscled appearance of the cows. This mutation also interferes with fat deposition, resulting in very lean meat. For this reason, the breed is presently maintained through linebreeding (what would be considered incest in human beings).
The cows are sometimes called “monster cows” and some countries’ governments, including Denmark, have advocated eliminating the strain.