Why will the wolf live peaceably with the lamb?
Radak #1: In the days of Mashi'ach, the nature of animals will return to what it was at the beginning of the creation and in Noach's ark. If lions and other predators ate lambs, the creation would be lacking, for they were born 1 only one male and one female per species. Rather, they are vegetation until their prey multiplied 2 . Also in the ark, we must say so, unless we will say that the extra six and six of Tahor species were for the predators to eat 3 .
Radak #2: This is all a metaphor. The wolf, tiger, bear and lion represent Resha'im who oppress and steal. Compared to the weak, they are like predators. The lamb, cow, calf and kid are a metaphor for the humble. In the days of Mashi'ach there will be Shalom, and man will not harm another man 4 .
Radak #3: The nature of animals will not change. Predators will tear and eat meat like nowadays. However, Yisrael are promised that evil Chayos will not damage in all of Eretz Yisrael, "Ki Mal'ah ha'Aretz De'ah Es Hashem" (9), since they are good, and they guarded Hashem's way. Chayos will not damage them, their animals and all their property - "v'Hishbati Chayah Ra'ah Min ha'Aretz" (Vayikra 26:6), and even if they pass through, they will not damage.
I.e. created. (PF)
We find that Chavah conceived and gave birth within one hour (Sanhedrin 38b). If also animals did so, we can say that the predators did not eat at all until their prey reproduced! (PF)
Rashi (Bereishis 6:18, from Pesikta Zutresa): There was a Bris that the Peros would not rot in the ark. (If this applied to all the food, we can say that Noach prepared meat for the predators for the entire year! - PF)
Radak: This cannot be, for it says "v'Lo Yashchisu b'Chol Har Kodshi" (9). In the days of Mashi'ach, there will be Shalom in the entire world - "Lo Yisa Goy El Goy Cherev v'Lo Yilmedu Od Milchamah" (2:4)!
Why does it mention a tiger with a kid?
Malbim: A tiger is the most brazen Chayah - even it will not damage even a kid, i.e. a nursing animal, which is easy to harm it.
What is "Meri"?
Rashi: It is a fattened ox.
Radak (7): It is a large [sub]species of ox.
Radak (7, from Targum Yonasan): It is a fattened animal.
Why does it mention a calf, young lion and fattened ox?
Malbim: Nowadays, a big ox goes with calves. Then, a young lion will be with both of them.
