It would make sense that giant spider hunt weak and small animals, like pigs, goats, sheeps and critters. This create another challenge for players to build extra protection for their animals

Spiders aren't regular farm animals, I think this is out of scope for this mod. But hold on till the devs reply.

Minecraft spiders, fantasy monsters that hunt even a human, will definately enjoy gnawling on some baby meat. This is another challenge, if you feel like only tending to animals boring.