Jack and Rocco were carrot fiends. You could never give either of them enough carrot.
Jake adored broccoli, but not the heads, just the stalks. He always left the heads, so my dad got into the habit of getting a large amount of broccoli for a family Sunday dinner, cutting all the heads off, and once a week Jake would get this huge broccoli stalk for dinner. He was such a damn picky eater otherwise though. I went through so many pellet and food mixes because he'd eat one for about a month then refuse to eat it ever again.
Comet and Blitzen...it's hard to be sure. There were always arguments over melon (of any kind), lettuce/cabbage leaves (not so much romaine, but definitely gem or savoy), but honestly I think that Blitzen's favourite was thyme. He was a major thyme hoarder. And if I only gave him small pieces he always came back to the bars for more which he really didn't do very often (preferring usually to nick Comet's food instead). Comet's favourite food was probably hay. I know, right? But no really, hay. He tried leaping off the sofa twice to get at the damn hay bag. And he frequently got tired of fruit treats and went back to his hay, so...yay for Nature's Own?
