Study veterinary medicine without a high school diploma?

I only have a vocational high school diploma, majoring in economics and foreign languages, and I'll be studying water management at a university starting in October. I'm just asking out of curiosity, because if I don't like the program, I'd like to study something else. Could I study veterinary medicine after two semesters, where I'd have enough or even more knowledge in the natural sciences and math than with the high school diploma? Would they make an exception? Or is there no way around the high school diploma or vocational training before hand?