I'm pretty sure the ponies of Equestria don't eat meat, for the sake of them being My Little Ponies. (even if the animators added in some things sometimes that resemble meat, I like to believe they are either plant-based or simply not what we think they are). Equestria has a moderate, nice climate (which the ponies completely control btw), so they wouldn't eat meat by choice. After all, herbivores despise the taste of phosphor.
Spike, however, is a predator. I'll be darned if this dragon doesn't NEED it. Every species with sizeable fangs needs to have meat, or they wouldn't have those fangs in the first place.