It is very difficult for foreign students to gain admission to US veterinary schools, simply as a result of the intense competition for spaces. There are only 27 schools of veterinary medicine in the States, all associated with universities.
Most students who enter veterinary school have completed at least 4 years of undergraduate education after high school and obtained a bachelor's degree. There are no veterinary studies at the bachelor's level. After 4 years of study in veterinary school, students obtain the professional degree, Doctor of Veterinary Medicine, DVM or VMD. Veterinarians must be licensed by the state in which they plan to work.
Students apply directly to veterinary schools; chances are somewhat better at private schools than at state-supported ones. The primary consideration for admission is the quality of the undergraduate record. Of the 27 schools, more than half require the Veterinary Aptitude Test for admission, 4 require the Medical College Admissions Test (MCAT), and a few require the GRE.
An alternative to veterinary school is to enter a graduate academic program in animal studies. Since this program does not lead to professional certification, competition is less.
For foreign-trained veterinarians with the equivalent of the DVM, there are two alternatives for postgraduate training in the US. Veterinary schools offer postgraduate academic programs leading to a Master's degree in veterinary science or to the PhD in conjunction with associated universities. These programs do not lead toward clinical practice, but rather toward teaching in veterinary schools, employment by pharmaceutical companies, or research.
Another postgraduate option is residency training leading toward board certification in a specialty, such as veterinary opthalmology or veterinary pathology. Residency training, also associated with veterinary schools, takes three years; it involves a combination of academic and clinical experience. Most American veterinarians do not elect to enter a specialty; rather, they go into general practice. Foreign veterinarians are occasionally accepted to residency training. Apply to the individual veterinary school which offers the specialty of interest.