How long have you been feeding that particular kibble? I tend to think dogs get bored eating the same thing every day food *too* long. I switch up the "flavors" in Cookie's kibble (many kibble brands have various protein sources to switch to). I know Merrick, Taste of the Wild, and Acana all have options to choose from and switch around. If I feed the same protein for too long, he lets me know. I don't switch it too much, I mean I will feed the same thing for a month, maybe two, but 99% of the time it does not hurt his digestive system at all to switch protein sources within a brand. Even between brands if the ingredients are comparable. The kibbles I choose are always grain free and have high quality ingredients so usually if I stick to that, he is fine.