Abrupt change in your dog's food is the #1 cause for diarrhea. It becomes a vicious cycle, where an owner sees loose stool or diarrhea, thinks it must be the food, and then changes food again.
When I adopted my foster Cahota, his well-intentioned previous owner left a note regarding "the only food he'll eat" so the next adopter would be aware. She wanted to find a food he seemed to like, and was shopping around different brands until he ate one with more enthusiasm than ones previous.
Especially when adopting dogs who are underweight, we feel nervous when they seem to not be eating enough. I think that is the prime inspiration to switching out food all of the time. The reality is, they will eat when they are hungry, and they can be brats about new food at first. The key is to find nutritious, appropriate food for our dogs and stick to it.
When we adopt a new dog, they tend to have been on a food that we don't love, or it's just not our food of choice. They key, is to slowly wean them off of the old food in order to avoid gastric upset. This is true of all food changes. The transition should take about a week. Slowly integrate the new food, in gaining portions, so their body can adjust. It almost seems silly, isn't all dog food sorta' the same? Not really. And, our pups tummies are much more sensitive than ours. We can eat any variety of food from day to day, but that is what our body is used to. Sometimes merely changing their treats can cause gastric upset and diarrhea.
My Cahota didn't love the food I feed my dogs at first. But with patience and not a ton of time, he learned to love it. He still doesn't always eat all of his breakfast, but his weight is fine. I sometimes add fish oil extract over his food, which encourages him to eat it all! But ultimately, he needs to learn to eat the food I give him; remind us of being kids? Parents don't cater their children's meals to what they "like", or else it'd be McDonald's every day. If your dog doesn't seem to like your nutritious food, they may be spoiled to a food that was more tasty, yet less good for them.
Transitioning our kitties diets is equally important, however unlike dogs, we cannot wait for them to eat if it takes a few days to adjust. Kitties bodies are different, and it is unsafe for them to go more than 2 days without eating. If your kitty doesn't want something, they won't eat it. Period. I learned that 1 bad experience with a food may be all it takes for your kitty to say "no way". By bad experience, I mean that one food may have been followed by an upset tummy that your cat will never forget. They may put their little paws out until the end of time over that food.
Always remember that while our dogs are a lot like us, their digestive system isn't. Constant changes in diet bring nothing but potentially negative results. Stick with the food you believe in, and when in doubt, ask your vet!
