I used to mow lawns. We would dump the clippings into a pasture to feed the cows. They absolutely loved it, and would come running when they heard our truck. The rancher told us to stop after one of them died of a weird illness. There's a a lot of nasty shit people spray on their lawns to make them look nice and green.
Just nitrogen for the green part. The nasty chemicals are for weed and pest control.