The Collaborative International Dictionary of English v.0.48:

Eatage \Eat"age\ ([=e]t"[asl]j; 48), n.
   Eatable growth of grass for horses and cattle, esp. that of
   aftermath.
   [1913 Webster]

WordNet (r) 3.0 (2006):

eatage
    n 1: bulky food like grass or hay for browsing or grazing horses
         or cattle [syn: eatage, forage, pasture, pasturage,
         grass]