dog mess

Well, all waste will eventually brake down of course but waste from creatures that eat animal protein ie meat is not generally used for it's potential health problems and the smell. If you do want to use it (I wouldn't advocate it personally) then you need to define the area and after so long, stop adding it as it will need quite a while, say six months to be left to break down.

Another reason I probably wouldn't use it is because there is little if any bulky material (plant material) in it which helps open the soil up. This is why horse manure is so good.

Another point, the bacteria needed to break any residual undigested animal proteins down into ammonia, then into nitrates (which is the sequence it goes through) are the ones that cause potential health hazards.

I simply wouldn't bother. It's just not worth it for what you get back.

Bag it and bin it would be my advise

The short answer to your query is - NEVER DO IT...for all the reasons given above. It really is too dangerous.
If you have so much animal waste that you are overwhelmed...then you could indeed get a Dog Septic System.
This deals with all animal waste and the enzymes provided "digest" the waste.....which then SAFELY soaks into the ground. The Wiggly Wigglers wormery people can provide a wormery that deals with dog waste..this is a newish product I have just heard about - haven't tried it yet!! You can always build your own version of a dog poo digester but there is of course a whole site you can go to which gives some other ideas ...including the new Dog Bog Bags that flush down the loo...yes they do! And they are recommended by NCDL etc!!

http://turning2green.co.uk/blog/2009/04/what-do-you-do-with-dog-waste/

Good luck!