In the anime, they got changed to Doberman Pinscher brothers named Thunder and Lector. Downplayed by breed in the sequel manga Ginga Densetsu Weed, where there are two English Foxhounds that trail Weed and his pack only to get killed off by Jerome.But in the anime adaptation, Rin is a feral dog instead. In the manga, Rin is a Japanese pine marten that attacks the Kai brothers when they're puppies, wounding them before Ben rescues them.In the Shoujo adaptation Cutey Honey Flash, she is a human. In the original Cutey Honey series, Cutey Honey herself was a Ridiculously Human Robot.
The Asuka of Rebuild is part of a series of clones similar to Rei. The original Asuka was, albeit a "designer baby", a naturally-born human.
May be part of Pragmatic Adaptation in live action movies and TV shows if the original species was either rare, dangerous, just not easy to work with, there was something else similar handy instead, or the original species was fictional to begin with. In the case of domestic animals, especially dogs, there can be an adaptation breed change. This is what's known as an Adaptation Species Change. You read a book about a hero and his faithful pet, but when the book is adapted to film, the hero's pet has been changed into a different species.