The barbed wire would worry me too. That stuff can be nasty and has done serious damage to dogs who hit it at speed. We also lost Sam for over an hour once most likely because his drag line got tangled when he went off the trail and out of sight. He made his way home but sans harness or drag line - never found them, either, though we combed the area he disappeared in. We assume he got tangled, eventually backed out of the harness, but by the time he succeeded he no longer knew where my wife was (since she was moving around looking for him - I was home recovering from surgery) and backtracked instead. Our local convenience store spotted him before he showed up back at our apartment, because we walk him down there frequently for quick errands, lol. He's a good boy, even if he scared us half to death.
On the other hand, loose dogs and horses can be a scary combo too. I remember watching a jousting show at a local Ren Faire one year only for someone's Boston to get loose and start tearing around the ring, hassling performers and their horses. Thankfully those horses were darn near bombproof but I was convinced I was going to see a dog get killed that day. It was "bring your dog" day, but that little guy had no business being there, he was clearly amped up and freaked out.
Sorry, rambling a bit. If you're good at following online classes and have the money to spend on it, Susan Garrett's Recaller's course is very thorough and builds strong recall through lots of games. Very much a 'you get what you put into it' scenario though, so it's not a great choice if remote, self-motivated training doesn't work for you. Control Unleashed is a far cheaper option since it's just a book, but also has a lot of valuable information on games and training to improve off-leash behaviors in varying scenarios, especially ones that are stimulating or stressful. It's aimed at sports dogs initially but helpful to just about any dog. Puppy Program is better than the original - it's more organized, essentially - but she has a new edition "from Reactive to Relaxed" that is the most up to date. Don't have that one personally though.