It depends a lot on the professors and content at both your undergrad and your vet school. I have not taken vet school microbio yet, but I doubt my undergrad micro class will really be that useful compared to the cell bio classes I took. At UMd, micro was a standard 200-level pre-med or bio major class (not all bio majors had to take it, it depended on your track within bio) with HUGE lectures and so-so labs. More to the point, when I took it as a senior because Minnesota requires it, I was pretty bored with the shallow level of detail. It was more about processes and general physiology, and we learned about staining and culturing techniques in lab, half of which I had already learned by working at a vet hospital only with nicer equipment. We did not have to memorize anything about particular bacteria, their pathogenicity, staining patterns, etc., save for some very basic information about genera. It's nice to know that stuff, but it doesn't get you very far ahead WRT having to know the pathogenicity/susceptibility/typical and atypical presentations in multiple species, transmission cycles, typical susceptibility patterns, etc. Ask around and see if you can peek at the syllabus - it sounds like other schools are very different.
OTOH, I am very glad that I took cell biology twice in undergrad - I took the 200-level cell bio and the 400-level cell bio (and I think I sat in on some other cell bio stuff). I am a big-picture person, and having to remember the minutiae of location signals on proteins and deal with cell cultures that died half the time made me a wee bit grumpy, but having that stuff hammered in before I had to take UC Davis' physiological chemistry definitely helped me visualize the pathways and put it in a different perspective that I could at least sort of understand. I also had biochem in undergrad but it was an accelerated version which did not help me as other people who had taken full-year courses.
I guess the point to my long, rambling post is that I think it really does help to take the most rigorous upper-level (at least at UMd, there definitely is a real difference on average in rigor and therefore future usefulness between 200, 300, and 400 level courses) bio courses you can (and do well in them, of course) in terms of having things make sense and making it easier to remember in vet school. YMMV, what do I know, I'm just a first year on leave, etc.