It is always great to add fresh ingredients to dog food! You just have to consider balance while doing so. Think about the dog food itself, it has been very carefully balanced with protein, carbohydrates, minerals, fats and vitamins etc. and just throwing on chicken and rice is going to 'rock the boat' on balance by increasing the carbs and protein, but not fat (since chicken is so low in fat) or many vitamins and minerals. You also have to consider the demands of a growing puppy, ESPECIALLY a giant breed puppy. The biggest concern with growing large-giant breed puppies and diets is calcium/phosphorous ratios and % protein. By adding chicken you are adding protein and phosphorus, but no calcium, that throws it off again. Now, for the brain teaser, it may be off balance, but dogs benefit so much from fresh ingredients that you need to consider if it is worth it to add it in or not. What I recommend and what I have done with my own dogs is add the the fresh stuff to the food, but balance it out first. It sounds like a lot of work, but it should be, there's a reason dog food bags have such long ingredient lists! If you are worried about it, I would recommend feeding canned food instead, but there are books out there that have recipes specifically for 'dog food toppers.' Hope this helps!
