When I first got Rowan, his foster mom told me that he had stopped eating the Canidae she was feeding and he was put on some sort of sensitive Iams or... something. I switched him off immediately when I got him so I don't remember. Those first couple years we didn't have any food issues. I had him on high quality kibbles that entire time. The only ones I remember specifically were Timberwolf (some sort of fish formula I think) and Nature's Variety Prairie/Instinct (I think I used both, chicken variety both times.) He also ate some raw, too, which was primarily chicken based. None of these caused him any issues. There was a period of time where I was really struggling financially, so he was eating whatever crap I could afford at the grocery store (so was I - lots of rice, discount bread, etc.) Not good quality foods at all, but they changed a lot. There were a few times where I'd offer food, and he'd look at it, sniff it, and walk away. This dog will bend over backwards for ANY food so it was concerning, but changing the food always fixed it. When I was a *little* more settled, I put him on Purina One Beyond, and after a couple months of eating that, he'd do the same thing - look at it, and walk away. I finally made the connection that every food he'd done that with had been chicken based. That was ~3 years ago. I haven't given him any chicken-based kibble since then, and we've never had a problem since. The weird thing is, I have fed raw chicken since then, and he's just fine with it. There never comes a point where he refuses it, nor does he act sick/uncomfortable in any way so I don't think it's just the novelty of it being raw meat that keeps him eating. I kind of thought that maybe it just had something to do with how chicken is processed when making kibble, but it seems like he only had issues when he was on lower quality brands, with the possible exception of the Canidae (I didn't observe that so I don't know if it was the same reaction.) He never had issues on Nature's Variety, for example. Could it have something to do with the quality of the chicken instead of the protein itself? This is all hypothetical because it's not really worth the risk to me to try him on chicken kibble again, but I'm really curious to know exactly what is going on with him.