Are there any advantages? If so, how much does it help?
Yes, attending UCD gives you an advantage.
See link: http://www.vetmed.ucdavis.edu/students/admissions/ClassOf2020Statistics.cfm
The two Cal Polys are also important feeders (especially SLO).
You will notice that the UCD vet school class of 2020 enrolled a total of 104 graduates from California schools. Of those, more than half (56 total) were either from Davis, Cal Poly SLO, or Cal Poly Pomona.
Vet schools want to see hands-on experience working with animals – and this typically includes large animals, not just doggies and kitties. It is much easier to get that kind of experience if you go to the kind of school that has big ag programs, with barns, stables, dairies, and livestock right on campus. Those kinds of resources are readily available in places like Davis or SLO, not so much in places like Santa Barbara or Irvine.