You could try adding some pumpkin to his food. Pure-not pie mix. It would also be good to give him probiotics and plain yogurt(tbsp.) to help the good flora in his system. When you do change foods, you need to do it gradually,and it's best to feed grain-free foods. Every dog is different and has different systems. The RC may be great for your friends dog-but may not be the best for yours. Many people here feed Fromm's. I feed Taste of the Wild/Salmon.