Belgian Blue

:  any of a breed of large beef cattle developed in Belgium that are blue, white, or blue-and-white pied and have an increased rate of muscle growth resulting from a mutation in the gene coding for myostatin Fed normally, Belgian Blues develop 20 to 30 percent more muscle than average cattle, and their meat is lower in fat and unusually tender. — John Travis, Science News, 22 Nov. 1997 Belgian Blues are unlike any cows you've ever seen. They have a genetic mutation that means they do not have effective myostatin, a substance that curbs muscle growth. — Nicholas D. Kristof, New York Times, 25 Aug. 2004