It depends how hard working the dog is. My dog either pulls a pulk or carries backpack, and then he needs much more calories on tour than usual. The food-brand I use for him has some highcalorie version, and on tours I bring this. Like OM my dog has a bit sensitive stomac, but when sticking to the same brand the change for my dog is so minor that he does not get problems.

I also raise the amount of food. He gets normally 300 grams (10oz) dayly, but on tour it is 500g. In addition he acts as my waste-bucket and gets all leftovers of the food I eat. I have calculated the calories for tours to the double.

Remember that some dogs have no problems at all to change food. My first two dogs were Siberian Huskies, and I could feed them literally almost anything edible. On one tour the SH I had did not eat "my" food at all, as she ate all the lemmings she could find on the track.