The horse I ride is a show horse; my trainer doesn't have any trails, but she does have two five acre pastures I'll ride him in every now and then. He loves
being out in the open, but he also is very prone to spooking- he's used to being able to see everything on the ground and not brushing his legs on tall plants/grasses. Grasshoppers were interesting for him to meet. While he's by no means dangerous
, it is more difficult to handle him out in the pastures than in the arena (at the canter; walk and trot he's still perfectly responsive).
There's no hard and fast rule that says a show horse can't be turned into a pleasure/trail horse. The only 'concern' I can think of is, like I said with my gelding, he's slightly more difficult to control because Look, all this open space mom! Let's go run! I can stretch my legs out real good!
. That open space is a pretty big deal to them; some might adjust easily, and others might not know what to do with themselves. Depends on the horse.
He's a Saddleseat horse, and the first time he saw the neighbor's cattle (there was a bull/steer [idk, something with horns] and two cows), you should have seen the look on his face! Momma, those are even bigger than I am! What are they?!?!