I believe you will find responses to that question in an earlier post below at:
http://www.dirtdoctor.com/forum/viewtopic.php?t=844
Unless there is something unusual about your dogs, the agent most likely is the excess nitrogen in the urine, and David's answer addresses that. The answer might be slightly different if they are Dalmations, but probably not much different.
As for the urine smell around the patio, if it is urine, that is addressed in this earlier post:
http://www.dirtdoctor.com/forum/viewtopic.php?t=956
Those answers probably still maintain even if the smell actually is cat spray.