lawn feed?

Is there a lawn feed that you can use that is ok for chickens?  

Yes we still have lawn, it's not gone, YET.  Hubby wants to keep it as long as possible and to be honest the girls are being quite good so far (4th week in)  

We have a border around the lawn that they love scratching in since I went around it with the trowel closely followed by 2 girls, they know the worms are to be found there now!