It's surely been a big debate about whether it is ok to feed raw and kibble, whether at the same time or not. I have not heard of anyone, despite all I have read to contradict such, that has had a problem feeding both at the same time (raw mixed with kibble) or a meal of each per day.Â
The arguments I've heard are that raw food digests faster and causes upset by leaving kibble in the stomach and the age old don't mix because you will cause a nutritional imbalace.Â
I did rescue a great pyrenese a couple years ago and she did best with a mixture of kibble and raw. If she got just one or the other she would have very soft, runny stools.  The Akita I fostered ate mostly kibble and got raw meat once in a while - no problem there, either. The Great Dane has also done well with a combination.Â
I suppose it depends upon the dog.