I prefer to ask to hunt in person, either catch farmers at the coop or go up to their house. You've got it made in that aspect, you'll surely see the landowner at the stables when you are checking your horse, just mention it in conversation. Ask something like, " would it be alright if I hunted out here sometime?" It's a nonconfrontational setup, and it doesn't sound desperate either. Don't be too depressed if they say no though, I know I wouldn't want ANYONE hunting on my horse pastures (I've actually shot at people who were). Ask them where it would be ok to hunt and what buildings or horses are around so that you can guarrantee that you won't shoot anything but deer or dirt, that's kind of a turn off on return trips if you shoot someones horse, or house for that matter!!!