Here's a link to a page with lots of ideas and pictures of the different veggies/ fruits too incase you're not sure what they are!
www.angeyswebdesigns.com/...nglist.htm
I aim to feed mine a minimum of five different fruits and veggies each day - a little bit of a few different things is more interesting for them than more of one type. Also, you don't need to worry so much about the possible effects of too much of one thing if there's less of it. The favourites in my herd (at the moment) are romaine, cucumber, parsley, apple, chopped celery, corn, broccoli, kale and melon. Remember to introduce new foods gradually so as not to upset their tums!
Treen
www.treenspigs.com/index.html