I saw this cow in the documentary, Bigger Stonger Faster (about steroid use and male body image issues in America) and was blown away.
Here’s more on the cow (called the Belgian Blue):
The Belgian Blue has a natural mutation of the gene that codes for myostatin, a protein that counteracts muscle growth. The truncated myostatin is unable to function in this capacity. This mutation also interferes with fat deposition, resulting in very lean meat.