Treat them as prisoners

"They're prisoners. Treat them as such. Feed them however much stale bread needed to keep them going, nothing more, and water. Keep them locked up in whatever cell we can find, and that'd be perfect."

"Yes, sir," the orc replies, cheerfully.

"Well, let's get into negotiations, shall we?" you say. "Organize an envoy to be sent to Lord Whitley. Spread the word we have these girls. If Whitley or any of his people want to see them again... well then, he better hand to me the keys to motherfucking castle."