Spraying hay fields

We have a good variety of hay fields on our farm. Pure timothy, pure orchardgrass, pure alfalfa, and alfalfa orchardgrass mix. We have some weed pressure. Mostly in the timothy, the crab grass comes back before the timothy and we can't get a 2nd cutting.
I have heard of some people spraying prowl on their hay fields to stop weeds from germinating. Has anyone tried this, or is there anything else I can spray on my Timothy for sure to keep the crab grass down?
Any ideas or thoughts on this will be appreciated.

Spraying hay fields