I try and keep away from dry food and stick with meats and veg.
Condition is a massive part as we all no. Iam no professional when it comes to dogs nutrition but iam when I comes to humans. Muscle is muscle tho no matter what is on I would imagine so long as getting protein like meats and that for muscle and recovery. Carbs like fruit and veg for energy and to help transport protein. And health fats like fish etc.....
And if wanted to go in to even more I start looking into amino acid build ups with its diet.