Hi there, I'm really sorry to hear that your results were not what you were hoping for.
Retaking year 12 is a good idea. Unfortunately however for your application this year you might struggle; it's very unlikely you'll get in with 'low grades'. Veterinary medicine is competitive, and grades is one of the first ways that universities can start whittling down the applicant pool. If you don't meet the minimum requirements then you won't even get an interview, sorry.
Usually teachers will predict you up to one grade above what you achieved at AS (so in this case BBC). Veterinary medicine requirements are around AAA (see
here for all of them), and I think you would struggle to convince your teachers to predict you much higher.
The previous poster has mentioned foundation courses. Nottingham, the Royal Veterinary College and Bristol offer a six year 'Gateway' program with lower entry requirements, however there are other requirements to this such as having a low household income or no history of parental further education, so look into whether you would be eligible.
So, an application for 2017 is looking sketchy, however don't be put off. A few people in the
veterinary medicine forum took A levels in three years, and another year will give you extra time to gather work experience to help your application stand out.
All the best
Again sorry to hear that you didn't get the grades you wanted today but it's by no means the end of the road!
I've just finished my first year of vet school so if you have any questions about applying/vet school in general do let me know