Force a manual refresh of resolver cache

I use fqdn in my firewall rules. To do so I had to setup a resolver and setup forward zones for all zones to a dns server I'm using that is not on the F5s. I and can set the refresh period to 10 minutes in the gui. It doesn't let me set the refresh any lower than 10 minutes. If I reboot the F5 the cache is cleared and doesn't populate until it reaches the 10 minute refresh period. So my firewall rules don't allow traffic until the resolver cache has been refreshed.

Does anyone know of a way to manually force a refresh of the resolver cache. I have been looking, but not able to find how to do this.