This feels like one where "kha hota" should be right? Big animals do not eat grass (habitually), rather than The big animals do not eat The grass? Or am I wrong?
The होता है form for stating a general fact only applies to adjectives, for example बड़े जानवर डरावने होते हैं, "Big animals are (in general) scary". It doesn't work with verbs.
खाते हें is the (masculine plural) habitual form of खाना - if you use होते हें it's the habitual form of होना, 'elephants are/be [habitual, not used here in English] grass'. खा होते isn't anything.
We can write it but generally while talking in hindi we dont say 'hai' every time when we are indicating someone's or any group's habit
Hope this will help