For almost a year now, I have been making detailed studies, guides, and charts for my version of mlp anatomy that I have been posting as rewards on my Patreon account. I have recently finished all three of the main pony tribes, and now that I'm done, I am moving on to the Alicorns.
Because I want to give them all unique anatomical features, I am going to be doing all of the princesses separately. Starting last month with Twilight, and continuing this month with Cadence, I will be doing complete anatomy references for one of the alicorn's every month. January will feature Princess Luna, and Celestia will be out in February. Iron-tier Patreons will get a flat-color sketch of the character, Bronze tier Patreons will get a shaded, labeled illustration, Silver tier will get the illustration, as well as the skeletal system, and gold tier will get the character, the skeleton, the muscle system, and possibly some other extras.
This picture here was left deliberately messy, and shows several layers of the anatomy at once. I will be uploading the finished images to my pattern account on the first of December.
To answer your question, I do head-canon ponies as being... sooorrt of omnivores. Real horses will actually eat meat occasionally. It doesn't happen often, but there are documented cases of horses actually scavenging off the carcases of small animals. It's kind of like when dogs and cats eat grass as a source of fiber. There are just some things, wether it's salt, protein, fiber or certain nutrients, that can only be gotten out of certain things.
I imagine that most ponies are "vegetarian" but not "vegan." Even in the show, we see baked goods, usually curtesy of Pinkie Pie, so they're probably using eggs to cook with, if nothing else, and Applejack presumably milks the cows that live on the farm. That means that at the very least, egg and dairy products are probably socially acceptable as foods, although most ponies diets would consist primarily of plant mater.
I also imagine that some types of ponies would have different dietary needs. Pegasi, due to living in cloud-cities, high off the ground, and not having access to farmable soil for most of their early history, might have evolved to do things like catch fish or hunt small animals, like birds. Having a source of food that doesn't have to be grown, which requires spending a lot of time at ground level, would be very helpful for a society that lives in the sky. I also imagine bat ponies would be genuine omnivores, if not outright carnivorous, eating meat as a large and regular part of their diet. (They will probably have fangs, when I get around to them.)
But for the most part, I drew the teeth that way because I wanted them to look slightly more human. It looks really weird if you draw a pony smiling, and there are huge gaps in the teeth.
Thanks for answering my question!
EDIT (PS): Now that you mention it, I do see the smaller gap. I just missed it somehow x.x