As others have said, you should be able to do all of the math/science you need in 4 semesters of full time course loads.
Depending on what schools you intend to apply to, and whether you have ever taken any college courses, it might take you an additional 2 semesters or so to get all of your pre-reqs done because the number of English and Humanities/Social Science or other elective credits required can be wildly different depending on the schools you want to apply to, so you would need extra semesters to complete those too, if you don't have them already.
Let's say you started this summer, your course load could be something like the below, and you would be eligible to apply to some, if not all, vet programs in the 2019 application cycle.
Summer Session 2018:
Chemistry I + Lab
Chemistry II + Lab
Fall Semester 2018:
Organic Chem + Lab
Biology course + Lab
Math
English Composition
Spring Semester 2019:
Organic Chem II + Lab
Biochemistry
Biology course + Lab
Additional English / Math / Bio Class
Summer Session 2019:
Physics I + Lab
Physics II + Lab
*Apply to vet school
Additional semesters - Fall 2019 + Spring 2020:
Any other classes you might need to apply for admission. Some schools require specific additional classes, and some require up to 30 electives in addition to their basic pre-reqs. Some of the specific additional requirements for various programs are: Cell/Molecular Biology, Genetics, Physiology, Microbiology, Animal Nutrition, an additional Math course, an additional English/Speech/Communication course, or humanities/social science courses.