You might consider checking out David Stripinis's book "The MEL Companion". He has a section in there where he talks about developing a grass generator. The melscript uses poly cylinders for the grass, so you can control the level of detail that you need. It also allows you to specify density, number, height, etc of the grass field. Not sure off the top of my head if it's setup to animate, but I don't imagine that would too difficult to add in.