At Isaiah 11:7-9, it reads:
"7 And the cow and the bear themselves will feed; together their young ones will lie down. And even the lion will eat straw just like the bull. 8 And the sucking child will certainly play upon the hole of the cobra; and upon the light aperture of a poisonous snake will a weaned child actually put his own hand. 9 They will not do any harm or cause any ruin in all my holy mountain; because the earth will certainly be filled with the knowledge of Jehovah (God) as the waters are covering the very sea." NWT
So how will "the lion eat straw just like the bull"? The context of the above passage shows that there is more to this prophecy than merely foretelling a time when animals will live in harmony with humans. Notice the last part of verse 9 as to what causes the transformation: “The earth will certainly be filled with the knowledge of Jehovah (God).” The knowledge of God does not change animal behavior. But it can and does change people. So this prophecy foretells that those who may have had aggressive traits or animalistic tendencies would put them aside and develop a Christlike personality because of learning and applying what the Bible teaches.
So people who may at one time have been of a beastly, animalistic, vicious disposition will come to be at peace with more docile fellow humans and will not seek to do them harm or injury.
The End of Evil Deeds Is Assured! (w10 9/1 pp. 5-9; Watchtower Online Library)
The Marvelous New World of God's Making (dg part 10 pp. 22-28; Watchtower Online Library)