I have heard or read somewhere that there were some questionable shots (most notably the kitten being thrown off a cliff, and the kitten in the river scene) in the Milo and Otis movie, so I wouldn't assume it was all shot humanely. I haven't seen this movie, the stories I heard about it totally turned me off to it.

Trip wires were very common in westerns and other movies, and it really hasn't been that long since they were outlawed. In the movie The Man From Snowy River (1982), a pregnant mare was run off a cliff and killed. One clue as to whether or not trip wires were used: If you see the horse getting to its feet after a fall, it was trained. If you don't see the horse get up onscreen, a trip wire was probably used. Many, many horses were killed or permanently injured using this technique in movies.