The moment of penis-into-vagina/anus being visible.
There's a little bit of it around, but for the most part, it's pretty damned rare to actually see the dog or horse or whatever's penis in the moment of actually entering his partner's body - It always seems to be either missed due to shitty camera work (I can't count the number of times I've seen a shot that looked like it was going to be near-perfect ruined because at the crucial moment, the camera jigs (or fails to follow the action - same result either way) so that all that can be seen is the penetratee's belly or leg, the dog's tail, the horse's inner thigh, the stall wall, the ceiling, the curtains, etc, etc, etc) or "let's cut away to the face, then not bother to include the penetration in the final edit" type crap. Or in the case of animals mating, particuarly in non-controlled breeding situations, it seems like there's some sort of "law of nature" in play that prevents seeing the penetration until after it happens - A fence post or wire blocks the critical instant, a tuft of grass or the branch of a bush blows in the breeze at exactly the right (well, actually wrong, since I want to see it) moment to block the view, sometimes (especially for prey animals like deer, sheep or goat-like critters, and other "wham, bam, thank you ma'am" style breeders) for long enough that the entire mating is finished by the time you can see again, or the shot is taken from an angle (which I understand - I realize how difficult it can be to get a good angle in a non-ideal environment, even though it drives me bat-shit crazy) where, based on what can be seen, the only thing that can be said with any validity is "The male mounted the female". Did he get inside her? Can't say - there's no way to tell based on what's visible. Did he just poke around a bit and jizz on the side of her leg? Can't tell - you can't see anything. Did he do her up the ass? Can't tell from what can be seen. And so on.
