Honestly, even if you have "enough" hours, you will probably want to keep on accumulating them. For me, much as I enjoy learning, when you are spending a lot of time studying things that at least at the time do not seem like they will ever apply to vet school or veterinary practice (a lot more than you think truly will- so don't get discouraged!), you can start to lose sight of what you are aiming for. Riding along on farm calls, assisting with the bull castrations or ewe c-sections or whatever it we are doing on each call is very motivating.
I'm in a special program for pre-vet students who want to do production medicine. My veterinary hours are lower than many because they want food/fiber animal vet hours and those are hard to come by in most places. I spend my breaks and summers shadowing.
However, I do have thousands of hours of animal experience, mostly in livestock. I did grow up on a farm, but until I was 14, all we had was a small poultry flock for eggs and meat and some gardens and a large field that was rented out. Then when I was 14 I got into sheep. I am the only person who cares for them and I am responsible for every single aspect of their management. VERY educational and a huge responsibility, especially at 40 head now. It's possible to really rack up the hours during lambing season, and trust me, you are WORKING. More like not sleeping, as Storyofmylife said about his/her foaling experience.
Some say that your animal hours should not be from your own pets, or at least to keep your pet experience hours very, very conservative. I take this to mean walking the dog and scooping the kitty litter...livestock management is a different category. But you would do well to try to get experience in different clinics, farms, shelters, etc.
Really, the main purpose for requiring hours as everyone else said is to prove that you understand the profession and what it entails. Most vet schools want diverse experiences. The program I am in is very different and solely focused on cattle, sheep, swine, etc. I do have plenty of small animal vet hours- just not as many.
If you are going to a land grant institution, you might be able to get a job on one of the university farms, caring for cattle, sheep, swine, horses, poultry, etc. Even if you feel you want to do SA only, it looks very good on your application to have LA experience.
Best of luck to you!