Have you never had problems with the dog hunting with food in his belly King?Something I've always avoided myself so would be good to hear your experiences.
Two slices of bread won't sit in the stomach too heavy, it's not like running them on a full belly of food which is a big no-no.
If you want to avoid the bread but still want to give the mutt an energy boost midway through a day/night out you could carry a few cubes of lard or dripping to give it, a nice energy boost with no heavy food sitting in their gut
Only 1 bit of brown bread Gaz so nothing really weight wise or size in the