That's because every owner thinks a big dog is going to poop all over the place & chew on baseboards, scratch doors & turn their nice home or apartment into a complete mess.
What you need to do in this techno-savvy age, is to do a video on yourself with your dog, tour you're would be landlord through your current home/apartment & show them that your place is immaculate, take other still photos of your dog, write a cover letter along with your rental application & get letters of recommendation from previous landlords that your dog is nothing to fear & he's a gentle giant.
If you don't have a video camcorder, ask your friends, I'm sure one of them do & they'll let you borrow it or film you with your dog themselves. Don't be surprised though, that the landlord will still want some sort of Pet deposit, maybe $500, so save up for that.
Realtor Since 1996
Main Street Realtors