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here's a wiki link to the breed http://en.wikipedia.org/wiki/Fighting_Cattleand a photo of the "entrecote" I had - I tried a bit completely raw before I cooked it and was very impressed - and it's much cheaper than normal beef!
I think the darker color of the meat is due to larger amounts of myoglobin in the muscle. It's due to exertion throughout life, not just exertion at the end of life.