Admission is extremely competitive, even more so than medical school. Your best chance of admission is at your state veterinary school. Many veterinary schools have agreements with states that do not have one. Read the entire section on medical school and heed the advice given there. The minimum course requirements for veterinary school are the same as for medical school, but there is more variability between schools for advanced courses.
Some schools require biochemistry and advanced biology courses.
Since most veterinary schools require the GRE, physics does not need to be completed before the end of the junior year. Schedule it whenever it fits best with your major and other required courses. It might be difficult to schedule all required, major, and general education courses if you are not a biology major, but it will not be impossible. Major in something you are interested in. Not all schools require an undergraduate degree, but because of the intense competition, very few students are admitted without a bachelor's degree.