I use zupreem pellets, mixed with nuts, safflower seeds, soy beans, nutriberries, etc.
They get bits of chicken and fish when I cook that stuff for us.
Lots of vitamin A foods, sweet potato being the all time favorite. You can cook one, and cut it up into cubes, and freeze it, then just nuke a couple of cubes in the microwave each morning - checking the temperature with your fingers - not too hot, or you will burn their crops.
Another nutritious favorite is warm oatmeal, again, not too hot.
Fresh fruits and veggies. Grapes, oranges, banana, apples. Broccoli, peas, corn on the cob, etc.
Expose them to a wide variety of foods when they are young and they will learn to eat just about anything you put in front of them.