He mentioned in the first episode we meet him something about someone finding a cure. When Rick mentioned the visit to the CDC Hershel still seemed insistant that someone will find a cure.
I imagine the barn contains family and friends lost to the walkers who Hershel believes can be brought back once a cure is found. He probably doesn't believe they are dead, but more like victims from "28 Days Later."
I see. So Hersechel doesn't believe they are dead. That Herschel wants them to disarm on his property makes sense now to the storyline. And now why he wants them to leave.
He thinks they can be cured, which is why he keeps them safe in the barn.
I agree that the story will go in that direction, Heshel thinks they are still curable, thats why he keeping them, but I find that really hard to swallow.
The man is a veterinarian , even if all he has ever done is work on farm animals, he has to understand the basics of mammalian physiology. A mammal cannot survive more then a few days without consumming water. He has to know the Zombies aren't drinking water, so he should
to know there is no hope.
And then there was his speech about comparing it to AIDS, he had a good point, afterall, remember when the government totally collapsed for serveral months due to AIDS and all near by major cities fell to the infected ; then , just like Heshel said, we found a cure and everything went back to normal?
Oh wait, that's not what happend... it's almost like a sane person would have a hard time drawing a paralell between AIDS and the Zombie Virus.