Trailer ad - Pretty sure I saw its twin this weekend. And I did a double take. I was very glad to see it was being used for moving inanimate objects and had no horse hauling charactoristics anymore. Not that this one does either
Donkey ad - 17 hand mammoth jack. Perhaps they need one that big to lift up the buses? From the pictures, it looks like wild burros just wander around their bus yard.
Mini stud ad - I'm pretty sure the sticker says "Upgrade Me!"
One horse trailers like that were pretty common right up through the mid 70s.
There is one still in use around here (PA/NJ) - I think they haul a mini in it - has the roof though
My first horse used to travel to shows in the back of a pick up - in NJ - large trailer box built over truck bed padding on wheel wells. In fact in the early 80s we went to a week long trail ride with a group of people. One was still using a truck bed trailer. Both were pretty well reinforced and did the job.
Worst "trailer" I ever saw was coming down Route 22 in Western NJ... A flatbed equipment trailer with horse standing on it attached to a lead line attached to a young teen boy sitting on a hay bale. Going west on the divided highway at about 50 mph YIKES