That's a pretty unfair comparison. Cows eat grass. Pigs and chickens are omnivores that can save themselves from the synthesis of a lot of protein building bl

That's a pretty unfair comparison. Cows eat grass. Pigs and chickens are omnivores that can save themselves from the synthesis of a lot of protein building blocks. Fish are cold blooded so they don't waste a big portion of calories that they eat keeping warm. Only the comparison between chickens and pigs is really relevant here.