But depending on how deep you would let the pig go, you may get some cum in the bladder and that would probably do a lot of damage. It might even clog up your urethra. I do not know how dangerous this is for the pig, but pig's penis seems to be quite flexible and does not have a bone inside.
Worm insertions are disgusting. I believe the worm dies too. Even though it is an insect and there are no higher cognitive abilities, I do not think it is right if something has to die for someone to have fun.
The idea of having cum injected into the urethra is yiffy, I kind of like it . But the safest way to do this is by using a syringe of some sort. Otherwise it is either dangerous for the animal or for you or both.
I'd really love to try this. And to be honest I think it would be easy enough to do. I've seen videos of pigs being milked and they do thrust at first, but then they seem to just be fine with relaxing while they dribble and squirt for a while. Plus if you got a pig young and got him used to hand jobs then you could let him breed your dick frequent;y enough to have him stretch you out.
As for the gel plug and getting into your bladder, I have no idea. My guess would be that a little pee and some sounding would get most if not all of it out. I'd also like to imagine that the plug has a natural tendency to dissolve in urine, I base this on the idea that nature seems to do things this way and if a sow got her urethra plugged it could kill her, so it seems like a logical evolutionary trait.
Take this with a pinch of salt as I only have basic knowledge of these kinds of things so I have no idea if it is accurate. Maybe I can fond out first hand one day though.
Injection of cum into urethra has been done by someone who slipped some sort of a silicone collection device that looked like a fleshlight with a tube over a dog penis and put the end of the tube into his own penis. There was very little risk for the dog as there was about 50cm of tube between them and there was obviously nothing in the dog's urethra (never do that ever).
I would also love to see this. Preferably a woman on the receiving end, but I'll take anything. Pissing or cumming out another animal's cum is a crazy-hot idea.
There is at least one guy I've chatted with who said he had trained a ram to cum in the guy's penis. He would then quickly mate with a ewe and on multiple occasions, get the ewe pregnant!