UDP is connection-less, meaning there is no such thing as true connection. You can limit packet rates of UDP though just like any other limiting. Use something like this if you are concerned about too many packets per second of UDP:
chain=input in-interface=1-coxBiz protocol=udp limit=5,5
connection-state=new action=log log-prefix="UDPLIMIT"
not sure the connection-state=new does anything but I think so if you have connection-tracking turned on. There really isn't such a thing as connections in UDP but the stateful firewall will keep track of them. You can see in the firewall / connections tab there are UDP connections being tracked, so as far as MT goes you can limit just like anything else.