Dvmcatdog,
While in veterinary school, you will learn a plethora of information about a variety of species: Horses, cattle, swine, small ruminants, reptiles, amphibians, exotic mammals, birds...and yes, dogs and cats. Veterinary school prepares you to pass the NAVLE, the North American Veterinary Licensing Exam- which qualifies you to be a veterinary general practitioner. On the NAVLE, you will be asked questions about food animals, companion animals, exotic animals- and the industries associated with these species.
Are you hesitant to work with larger animals? If so, and you're a pre-vet, I would highly suggest finding some shadowing experience with large animals prior to jumping head first into vet school. You will be expected to handle big critters- horses, cows, pigs, etc. Also, little things that can bite- like rats, snakes, etc. It's important for you to know as a potential veterinary student that your love for animals extends to all species. Most of us have a passion for one group of species or another (or perhaps an industry), but I'd put it out there that the great majority of us have an appreciation and respect for all animals.
You'll want to get on board with that mentality before applying to veterinary school, and certainly prior to matriculating. Your classmates (who may have more experience with some species than you do), will be more than happy to lend a helping hand, but you'll need to jump in there and castrate, palpate, cast, etc. Make sure that this is something you can see yourself doing before signing up for vet school.