I would guess that OP means to improve their application before they apply again.
I had played with this idea before, and I also found the Certificate in Veterinary Medical Science through Drexel University.
Have you already taken into account the timeline for applying/being accepted into these one year programs compared to the timeline for vet school? If you have already passed the deadline for admission into these other programs, then you might have a year of doing nothing at all until you apply to vet school or the other programs again.
When I was considering this, I determined that I should have apply to a Master's program at the same time as I did vet school, in order to try and guarantee that I would be doing something in the gap year between when I apply to vet school and when I would hopefully matriculate.