The biggest question is how large the cage is. Crowded quarters will cause the adults to nibble the pups' ears.
I'm more concerned about the presence of the boar than of the other sows. If you separate the sow from the herd, you're going to have to wait until the pups are several weeks old and then do a herd-to-herd reintroduction, which can be a big hairy deal and may fail. If it were me, and if I were going to remove anybody, I'd remove the boar and put him in a cage right next to the sows. Then you only have to reintroduce the boar to the herd, and a one-to-herd introduction is usually MUCH easier than a herd-to-herd.
However, I hope someone who's been in this situation will reply about the need to even separate the boar. They're not usually aggressive, and I really have no idea whether there's any possible danger to the pups in leaving him in the cage. Anybody out there have experience with this?
