I have had my colony for well over 2 years now. I have found they prefer fruits and veggies over foods with higher protein contents. The dog food I use is moisened dry dog food. The brand is Iams. When they had a choice they always chose the fruits and veggies over the dog foods. I have tried many different brands of dog foods, all with the same results.
I still offer them a choice and almost always throw out left over dog food.