The field of veterinary medicine has rapidly evolved. The days of treating both pets and farm animals have given way to specialization and sub-specialization. Specialists can be divided into small animal, large animal, and exotic animal practitioners. An example of subspecialist would be veterinary neurologist.
Regardless of your interests in veterinary medicine, you will have to study both large and small animals. Many pre-veterinary students have experience with small animals, but limited experience with large animals. The University of Charleston has developed a unique pre-vet program designed not only to meet the pre-requisites for veterinary school but to gain expertise with large animals.