Translation:I am so hungry that I could eat a horse.
There is a similar expression in Polish (and probably in other european languages as well, including English : http://en.wiktionary.org/wiki/I_could_eat_a_horse), and we even add "with hooves". Noone is eating horses here ( at least not on purpose) and horse meat is not part of polish cuisine.
Actually, yes. Cheval here is meant to be seen as a big quantity of food. (That's the way I've thought about this idiomatic expression since childhood.) You could say "J'ai si faim que je pourrais manger un éléphant" without changing the meaning.
However, mptmpt's comment had me thinking about the "taboo" implication of eating a horse. I guess a city girl like me didn't consider the bond between the horse and its owner.
The Present Conditional form of most verbs uses "would" + verb. Two notable exceptions are pouvoir (all cases in Present Conditional use "could" -or- "would be able to") and devoir (all cases in Present Conditional use "should" or "ought to"). Source: Barron's 501 French Verbs.
I'm going to argue that "je pourrias manger un cheval" is literally "i would be able to eat a horse" and is the same thing as "i could eat a horse." In support of my contention, DL itself gives both "would be able" and "could" as acceptable translations in their "we could live here in peace" example.
Speaking of literal, the introductory clause is literally, "I have such hunger ..." but DL shot me down on that one too!