Various mobs grazing code

How can I code the behavior of some other particular mobs (if they normally do not) that they would be grazing just like sheep do? I'm using Tynker to modify some mobs for my purposes and for the challenge they have to eat the green surface that is covering dirt blocks just like sheep do. Is it (will it sometimes) be possible? Funny, but sheep itself is taken out from Tynker Mob templates...