No, that horse wasn't supposed to be undead... If it looks like that to you, then I guess it's just my poor drawing. He shouldn't look underfed, so if he does it's because of my mistakes.
Don't beat yourself up. It's just the wrinkles on his sides could almost be taken for ribs, but a second look disproves the notion. At any rate, you draw a better horse than I could hope to.