Usually when someone says "not to be rude," that's a signal they should reconsider what they're about to say, because it's usually rude.
Anyway, <IF> you get in, the grades shouldn't matter and you can slack off as long as you pass with whatever minimum is required by the vet school that you are assuming you will get into.
But, I agree with the two other veterinarians who have already answered that said a) you can't assume you'll get in, and then they will matter, and b) this material matters in vet school - you think you're working hard now, just wait until vet school... so learn it well now and it will just ease up the biochem in vet school.
I can't say I have direct experience evaluating academic qualifications of applications, but I have done vet school interviews (as an interviewer and as a candidate), so I do have a bit of experience with the evaluation process. Not to mention, of course, having gone through it as an applicant/student. Not to be rude....