In Eden, they were to be vegetarian -if not vegan. Even the animals did not eat flesh.
After the flood, God allowed all things -including animals flesh -to be eaten.
With the Mosaic laws, God allowed only some types of animal flesh to be eaten.
It is very clear that animal flesh was considered clean by those laws -which even make specific mention of the various animals.
However, in the kingdom of God on earth -yet future -even the nature of the animals will be changed so that they do not eat meat.
It it specifically stated that the lion will eat straw like the ox.
While it is not specifically stated, it is unlikely that the humans who repopulate the earth during the thousand years after Christ's return will kill and eat animals.
The food issue has generally followed man's spiritual state. No meat, all meat, some meat and then none again.
Gen 1: 29 Then God said, "Behold, I have given you every plant yielding seed that is on the surface of all the earth, and every tree which has fruit yielding seed; it shall be food for you; and to every beast of the earth and to every bird of the sky and to every thing that moves on the earth which has life, I have given every green plant for food"; and it was so
Then.....
Gen 9:
3Every moving thing that liveth shall be meat for you; even as the green herb have I given you all things.
4But flesh with the life thereof,
which is the blood thereof, shall ye not eat
Then.....
Deut 14:4 These
are the beasts which ye shall eat:
the ox, the sheep, and the goat, 5The hart, and the roebuck, and the fallow deer, and the wild goat, and the pygarg, and the wild ox, and the chamois. 6And every beast that parteth the hoof, and cleaveth the cleft into two claws, and cheweth the cud among the beasts, that ye shall eat. 7Nevertheless these ye shall not eat of them that chew the cud, or of them that divide the cloven hoof; as the camel, and the hare, and the coney: for they chew the cud, but divide not the hoof; therefore they are unclean unto you. 8And the swine, because it divideth the hoof, yet cheweth not the cud, it is unclean unto you: ye shall not eat of their flesh, nor touch their dead carcase.
9These ye shall eat of all that are in the waters: all that have fins and scales shall ye eat: 10And whatsoever hath not fins and scales ye may not eat; it is unclean unto you.
11Of all clean birds ye shall eat. 12But these are they of which ye shall not eat: the eagle, and the ossifrage, and the ospray, 13And the glede, and the kite, and the vulture after his kind, 14And every raven after his kind, 15And the owl, and the night hawk, and the cuckow, and the hawk after his kind, 16The little owl, and the great owl, and the swan, 17And the pelican, and the gier eagle, and the cormorant, 18And the stork, and the heron after her kind, and the lapwing, and the bat. 19And every creeping thing that flieth is unclean unto you: they shall not be eaten. 20But of all clean fowls ye may eat.
21Ye shall not eat of any thing that dieth of itself: thou shalt give it unto the stranger that is in thy gates, that he may eat it; or thou mayest sell it unto an alien: for thou art an holy people unto the LORD thy God. Thou shalt not seethe a kid in his mother's milk
Lev 26:21 If then, you act with hostility against Me and are unwilling to obey Me, I will increase the plague on you seven times according to your sins.
22'I will let loose among you the beasts of the field, which will bereave you of your children and destroy your cattle and reduce your number so that your roads lie deserted.
Then......
Isaiah 65:25 The wolf and the lamb will graze together, and the lion will eat straw like the ox; and dust will be the serpent's food. They will do no evil or harm in all My holy mountain," says the LORD.