Where did you “find out” that all jockeys (as you suggest) “zap” horses as they break for the gate??!! That is simply NOT true. I get very frustrated when myths are spread as facts. Some jocks have been caught with buzzers they mainly use in the stretch for that final push - but they are the extreme minority and get busted for it.
I also had a TB explode and bolt from hearing a bug zapper next door. He had never been in training or at the track or had any kind of device used on him. He had the same reaction to a hot wire snapping/zapping - so may have gotten his nose too close to one in the past… and had a good memory.