I don’t think the link to the thread on “incest” was much help, either.
I’m not a dog breeder, so I don’t know for sure, but it was my impression that artificial insemination for dogs is impossible, because while two dogs are mating, the male dog doesn’t ejaculate for several minutes. The bitch’s vagina closes around the penis, locking it in place–dog breeders call this the “tie”–the dogs are literally “tied” together. Then they remain that way for anywhere from 10 to 30 minutes, and at some point during the proceedings the male ejaculates and he hops down.
So, for this reason, you can’t collect semen from a dog to use in an artificial insemination program. Nobody really knows why the “tie” evolved.
To breed a male chihuahua to a female St. Bernard, you’d have to stand there and hold the male until it was over, or prop it up on a table or something. And why would you want to to something like that?
I don’t think it would be physically possible to do the opposite, to put a male St. Bernard to a female chihuahua. I once saw a male chow doing it with a very small female Heinz 57 lap dog, and it wasn’t pretty. He kept trying to move off (because the bitch’s owner and some concerned neighbors were pursuing him, but that’s another story), and he didn’t seem to understand (or care) that there was an 8 lb. bitch dragging around on the ground, stuck onto his penis. She sounded like it really hurt, too.
As to the size of the resultant (hypothetical) hybrids, if a chihuahua weighs 2 lbs. and a St. Bernard weighs 100 lbs., and if you average the two, you end up with a dog that weighs 51 lbs., or about the size of a boxer. I’d think you’d get what Milossarian called a “funky mutt”, sort of a St. Bernard-looking dog, about the size of a boxer.
I sincerely hope no Dopers try this at home. 