I can't remember exactly how many hours I put down, but I'll try...
Non-vet shadowing experience:
Small animal: thousands. I'm a behaviorist, I foster for a national rescue and the local humane society, I've done several dog sports (Schutzhund, agility, etc), yada yada yada.
Large animal: not much.
Equine: took riding lessons back in the day. I estimated 300 hours.
Exotic: own and have owned numerous exotics (snakes, rats, mice, birds, ferret, rabbits) and have fostered a few for the local humane society (mostly guinea pigs)
Vet shadowing experience:
Small animal: several hundred with several vets, including an Army vet.
Large animal: several hundred with a mixed practice vet, mostly dairy and beef cattle. Also helped the vet with a sheep and goat sale.
Equine: not a whole lot (a few farm calls was it), but with that same mixed practice vet.
Exotics/zoo: did 25 hours at the Omaha Zoo
Lab animal/research: did several thousand hours of research during undergrad and grad school, including a collaborative research project with the head vet of the Research Animal Diagnostic Lab (RADIL)