Can cats eat dry cat food and wet dog food?

I take care of 6 semi feral cats I feed them dry cat food and wet food daily. The biggest can for cat food is 12 ounces and 22 ounces for dog and it's the same price. I was wondering since dry food is their main source of food would it be ok to feed them canned dog food once a day? If not I know I can get a 22 ounce can of cat food for the same price but it does have tuna in it which I know isn't good but since it's just one meal maybe not terrible.

I would not be feeding them dog food.  Tuna would be better than dog food.  Have you checked prices online?  Petflow.com offers 10-20% coupons weekly.  Also Chewy.com and Amazon.com have decent prices too.  Petflow and Chewy both offer free shipping on orders over $49.

If you want to slip a can of dog food in now and then, it won't hurt. My cats just go crazy for canned dog food. .. what's in it anyway? So I do let them have a can occasionally. But not on a regular basis because it doesn't have the necessary taurine and the mineral balances may be wrong for cats. The tuna in the big can of cat food will be better than dog food on a regular basis.