Myostatin is an interesting protein. It plays a crucial role in muscle development; namely, it limits the growth of muscles past a certain point. Thus, if one blocks myostatin, then muscles continue to grow bigger and larger than they're supposed to. Certain breeds of dogs have been bred for mutations in the myostatin gene, and recently, drug companies have begun to manufacture myostatin inhibitors for lazy bodybuilders, but also as a potential treatment for muscular dystrophy.
But myostatin mutations are also found elsewhere. Meet the Belgian Blue.
The Belgian Blue is a breed of cattle that has been selected for a naturally occurring myostatin mutation. The result is, quite obviously, a rather beefy (pardon the pun) cow that produces lean meat (since the mutation also interferes with fat deposition) and lots of it.
Perhaps it's the carnivore in me speaking, but I think that might be the most awesome breed of cattle. Ever.
Now I have a craving for a big, juicy steak...
A nod to Sentient Developments for bringing this massively delicious specimen to my attention.