Discussion over beers turned to rodeo, specifically bull riding. I thought I had heard that bulls were electrocuted on their testicles just as the gate is opened. This is apparently a mixture of partial truths. The bulls do have a flank strap which some people have thought causes pain to the bull's testicles, however here's the info on the flank strap:
The flank strap is often misunderstood. Its purpose is to entice the bull to kick more. Without it, most bulls would have greater tendency to run or fall. The flank strap serves to regulate their bucking somewhat and cuts down the risk of injury to a bull. If you are familiar with a dog's ticklish spot, then you have an understanding of how a flank strap works. Bulls and horses are notoriously ticklish around the flank area.
There is also an electric shock involved in getting the animals fired up, illegal however in most places. Almost all the information I can find on the internet is about animal rights abuse. Apparently the 'hot shot' delivers 5000volts. It is applied to the rear end of the animal just before the gate is opened. video.
Not quite as bad as getting it straight to the genitals but it sounds uncomfortable. I'm not going to weigh in on the moral issue but I find watching the bull riding entertaining( video -NSFW because of soundtrack = footloose). I think I cheer for the bull though....