Ahh. This is the kind of cc I'm looking for. Regarding the blown out background, using a flash or reflector would have helped then? I'm such a noob.
Hey, don't worry about being noobish.
So let's say that most conditions remain the same; (the horse's position relative to the background), and you wish to increase the light on its head and decrease the background.
I tried to read the EXIF, but it was stripped, so just guessing here.
You would "increase" the shutter speed (decrease the time being open) (yeah, confusing, I know) which lets in less light overall. Then you use a strobe bounced off a large white something (white foamcore, white tee-shirt, whatever) and adjust the aperture to make a good exposure of just the horse's head (which is lighted by the strobe light).
All that preparation takes time, so anything you can do to be prepared ahead of time will help. Carry your flash with you. Be aware of lighting conditions changing as you move from one place to the next. If you can ask the horse owner to hold him in the doorway for a minute, make some quick adjustments to your camera, the flash, and get someone to hold a reflector for you.
While this might all happen within 30 to 40 seconds, being familiar with your camera, your flash, what initial settings might be needed, etc. will all help with the smoothness of it all happening. You might even have enough time to whistle softly to get the horse to raise his head and point his ears toward you.
Good luck!