Hi,
Catfood is not good for dogs, Catfood is higher in fat. It does not contain the appropriate proportions of essential vitamins, minerals, and nutrients. It will Not hurt the dog to get into the catfood once in a while but it should not be eating it daily.
Also If you are cats are 100% carnivores, Dogs are not totally 100% carnivores.
Having a problem feeding your dog his proper food try placing the catfood somewhere where he can not get at it. I have mine in the basement and Presley can and wont go down there as it is blocked off with a baby gate

Also cats can not produce their own source of taurine. They get the extra taurine from the catfood.. Dogs on the other hand do. A lack of taurine can cause blindness and heart defects