Of course, to worry much over this small dietary detail, one would also have to believe literally that the Noachian flood covered all the highest mountains on earth, killed off all vegatation, and diluted the salt water seas.
Also that ancient people lived from 600 to 900 years in those days.
To believe the equally fantastic JW beliefs on the subject - all animals, including those obviously designed to be only predators, were somehow vegatarian plant eaters in the days of Eden.