Is this sentence for real? xDD The horse is eating my scarf. WHEN will I have to say this?? LOL Well, I don't know Sweden, maybe this happens a lot there.
It's really hard to say this in a truly idiomatic way in Swedish, for lots of reasons. Most importantly, you should probably have the particle verb åt upp (stress upp) here. Let's say Hunden åt upp min läxa, it's still not an unproblematic sentence, but I guess it will have to do.
I think what happened here is that the original example about the horse eating a scarf got mixed up with my question about how to say "My dog ate my homework". "My dog ate my homework" is a kind of American cultural joke that refers to the ridiculous reasons that students give for not having their homework done when they arrive at school.