I don't think they are recommended for use as the sole diet, but I think most canned foods come to about 1 can per 15 lbs of body weight. You might see if they list the calories and compare to other canned foods that provide guidlines.
According to their website, the EVO 95% Beef Canned Dog Food can be used as a complete diet. "Use EVO alone, or as a supplement to your raw or home cooked pet food for a complete and balanced natural feeding." http://www.evopet.com/products/default.asp?id=1493
You can probably get your questions answered by calling Natura's Customer Service - their 800 number is listed at the bottom of their home page. http://www.naturapet.com/