Horses graze with deer/antelope/elk all the time out here. From my front window you can watch then eat my hay together.
Out back you can see them drink side by side out of my water tank.
I've ridden right up to deer in my back yard.
No sir, deer aren't spooked by horses.
West of town where I hunt antelope there is a pretty large horse ranch. You really have to be careful as the antelope get right in there with the horses.
You can get on the opposite side, using your horse for cover and get pretty close to antelope. Thing is antelope don't know how many legs a horse has.
CPT USAR Ret
USAMU Sniper School Oct '78
Distinguished Rifle Badge 1071