Being from an area that has a lot of whitetail hunters and it is only legal to hunt with a shotgun, there are a huge amount of slugs available. Everything from cheap-o Wolf, to simple Foster style slugs from Winchester, Federal, Remington, Brenneke, to sabot slugs, to top of the line Barne's Xpanders, Hornady, etc. There is even a 3.5" 20gauge slug some folks use (yes a 3.5" 20 gauge, not a typo).

My point is that there is a growing industry in the States with slugs loads and guns. I have personally killed whitetail deer at long distances (long for shotgun) with good slugs in fully rifled shotguns. I have cleanly killed deer at 136 and 165 yards. These were laser ranged, I had a VERY solid rest, and knew my gun/slug combo VERY well. I would not suggest this is the norm, and most won't do this mainly because of lack of knowledge.

As for slugs on hogs-- I'm not sure what you have available there, but in the States we have some very effective loads. If you want penetration, there all solid copper and hard cast lead. There are lots of pigs killed here with slugs, and I would suggest it should be more effective than buckshot, especially at longer ranges.