You Are What You Eat Eats  There's no such thing anymore as just
eating a steak. Was it grass fed? Did it have a hobby? Now,
thanks to a group of Irish chemists, you'll never have to worry
again about your Porterhouse's diet. Just your own.  Turns out
that the proportion of stable isotopes of oxygen, nitrogen,
hydrogen and sulfur found in the posthumous muscle tissue and
tail hair of cattle can tell you a lot about what animals ate
before landing on your dinner plate—and in some cases, where
they ate it:  Certain diets yielded a distinctive signature, the
researchers report in the Journal of Agricultural and Food
Chemistry. They couldn't tell between animals that ate from a
pasture and those that ate grass silage, but there were clear
differences between animals that ate pasture grass and those
that ate concentrated food products. Using hair and tail
samples, they could even follow changes in an animal's diet over
the course of its lifetime.  I'd say that having that much info
gives you an unfair advantage ov