I firmly believe that if you feed your dogs a variety of food (assuming the dog does not have a sensitive stomach to start) and without 'catering' to a fussy dog (eg introducing new foods only as a way to try and get a dog to eat) it will eat almost everything with no fuss or bother.
Dogs have very tough stomachs and simply changing a food, unless you only ever feed one brand and flavour kibble entirely on its own, should not bother them one bit. Consider what dogs will happily eat -- trash, old bones with decomposing meat they have buried ages ago, things children drop, scraps, dead animals they find, cat and other animal feces, raw meat...! All with rarely any problem at all (as I know from experience, having had only ONE incident of one dog getting stomach upset from something eaten off the sidewalk).
If you only feed one brand of kibble, then do try to change over gradually. I have always understood the reason for doing this to be more to get the dog to accept a new food tastewise, rather than anything to do with stomach sensitivity.
I know breeder Laura Lang regularly rotates dry and feeds a wide range of foods. Her dogs will eat just about anything, from salad greens to raw to cooked to dry to tinned to fruits and veg. They do not have any problems. I followed her feeding advice and ditto for me; I feed all the above. Mine will eat anything. I alternate meals from day to day or sometimes week to week though I'd never feed the same thing in a row for a full week. The dogs are very easy to board or kennel as a result. I have never ever had anyone turn up a dog nose at a bowl of food, except Jaspar when he was a lone pup and prone to playing food games.
Typical meals:
- chicken or turkey homecooked stew (with veg and rice or barley or oats)
ground beef stew, with veg and grain
raw chicken necks
raw chicken wing pieces
kibble with sardines or egg
kibble with added cooked beef, chicken or other meat
kibble with banana
leftovers
To any of the above, added fruit pieces, veg, yoghurt, cottage cheese, egg...
The one thing I have seen make dogs get stomach or bowel upset is very poor quality kibble or tinned food. :yuk: