They way I look at it, increasing the air flow maintains fertility. Seeing as they are caged all day, it's only free to let them wonder about during the night.
"And where do you think you're going, Mr Testicle?"
"I'm off to get a drink of water!"
"No you're not, come back here right now. You know what happened last time you ventured out alone."
"Oh yeah. That bloody dog."
"Take the taser with you this time."