After my 1st application cycle when I applied to 5 schools and didn't get a single interview, I did file reviews with Cornell, Colorado, and Tufts. They all said pretty much the same things.
What I took away from my reviews was that I didn't get in because of
* low undergrad GPA
* vet experience not diverse enough
* not enough community service/activity
All my reviewers said my GRE, LORs and PS were excellent. My problems were that I only had small animal shadowing experience and tons of hrs in lab animal work, but no LA, shelter, or zoo experience. Also while I had a 4.0 in my pre-req post-bacc work, my undergrad GPA was a 3.25. While I couldn't do anything about my undergrad GPA, one of the reviewers gave me great advice. She also said that they were impressed with my post-bacc work, but since I had been taking 1-2 classes a semester while working full time, they weren't convinced I could handle a full class load.
I spent the next year getting horse experience, working at a cat shelter, being more active in the community, and I went back for a full semester while working part time (not even pre-reqs, just classes "for fun" - hah!).
It must have worked because this time I got 4 interviews, 2 acceptances and 2 alternates. It just goes to show that even when you have a low undergrad GPA, you CAN do things to improve your chances!