As long as you are feeding a food that is nutritionally complete, feeding dry only is fine. If you look on the label it will tell you if the food is complete. Complementary foods are usually things like mixers and biscuits and they have to be given with a canned food in order to make a nutritionally complete meal. Do make sure they have plenty of clean, fresh water to drink as there is very little moisture in dry food - most contain about 8-10% moisture which is not enough to meet your dogs' fluid requirements.
By Libby Sheridan (Hills Pet Nutrition) (Professional Advisor)