This is exactly opposite to what the Hebrew Bible tells us. According to that tome, every moving non-aquatic creature’s antediluvian diet was green herbs (Gen. 1:30, 9:3), including tyrannosaurus rex as well as homo sapiens. Interesting —
It's safe to say that conditions and the nutritional content of plants was significantly different pre-flood, insofar as meat was not on the menu, for it was unneeded. In addition, pre-flood biblical characters lived significantly longer than post flood ones.
I'm not a bible expert, but I seem to remember that Abel became a shepherd of a flock, while Cain cultivated the land. I don't think that it's too much of a stretch to assume that the flock was used for food, and also for offerings to the Lord.