Just a general question about trophic levels. Traditionally, it's thought as much as one order of magnitude of energy is lost as one moves from trophic level to trophic level. I am confused here since it seems to me the energy content of certain primary consumers is more if not equal to an equal number of producers. Take a 1 acre lot of grass vs a 1 acre lot of cows; surely the calorie content in the cows is more than that in the grass no? A one ounce cut of beef has more calories than an ounce of grass. I could imagine for plankton or insects, maybe the energy content is not as conserved since they can store less energy and eat less. So my question is whether this one order of magnitude drop is a rule or just a 'rule of thumb' or if I'm framing the whole thing wrong.