I wouldn't use dog or cat food. There are a lot of things that get mixed in that aren't good for ants. I've been told by a few knowledgeable people that it
can cause a colony to die off.
I guess that depends on your country. In my country the regulations for dog and cat food are actually stricter than for human food. The major issue I see could be salt (and some cat/dog food has vegetables mixed into it but they aren't even good for cats and dogs so forget about these), but the amount of salt in the food is noted on the can and if the ants have enough water they should be able to deal even with more salty food it. Someone in the forums (forgot who) has a giant invicta colony and feeds them half a can of dog food per day and they're doing fine.
Which country are you from? I find it hard to believe that your government would put animal food safety before human food safety.
It's not the salts its the contaminates that make their way into the food during production/handling, or the neglect of the companies when sourcing the ingredients.
They do not use the best materials to make the food, they use the scraps and leftovers, anything not fit of human consumption.
You said yourself they make cat/dog food that isn't even healthy them. A lot of the cat/dog foods are heavily contaminated with unhealthy things and I personally don't think it is a good idea to use as ant feed, or animal feed for that matter.
That's not to say there isn't any good cat/dog foods, if you want to spend the money you can get all natural healthy foods but if your going to feed them chicken cat food, why not feed them actual chicken?
The person with the invicta colony, may feed them some dog food but half a can a day seems a little excessive, and a doubt it is their only protein source. And that's not to say there aren't a few exceptions in the ant world that can sustain on unsatisfactory foods.
See here: http://www.littlebig...d-contaminants/
Current queens/colonies
Camponotus novaeboracensis x2
Camponotus pennsylvanicus x2
Camponotus herculeanus x1
Formica sp. x1
Lasius americanus x1 (Lasius alienus)
Lasius neoniger x1
Crematogastor cerasi x1
Myrmica sp. x1