First of all—congratulations on your decision to join the veterinary field. As a veterinarian for almost 25 years, I can say without a doubt it has been a very rewarding career. Like you, when I first started, I had no experience with equine and large animals. I was able to find a mixed animal veterinarian to shadow and this helped me tremendously. I went on farm calls with him and it was a great learning environment and eye-opening experience about the life of a mixed animal veterinarian.
Most veterinarians are happy to help future veterinarians and welcome shadow opportunities. If that is not an option, then try to find a farm or horse-riding facility where you can volunteer to help. This again can be a great opportunity to just be around the animals and get more comfortable in their presence. In my case, once I got into to vet school, I enjoyed my rotation in equine medicine so much, that I nearly opted for equine medicine as a career, never having been around horses before school! You never know what direction veterinary medicine will lead. Best of luck!