I had been feeding my dogs sardines for awhile and recently had to cut them off completely due to financial problems so I have gone back to feeding fish oil capsules and got a few tins of herring for the dogs this time because there weren't any sardines at the store. From my knowledge, herring and sardines are within the same family being that sardines are just a younger version of herring, correct? What I wanted to know if herring is any more rich, or just to some dogs at all than sardines? My Hanna has been throwing up and having the runs today and I know it's from introducing the herring last night like I used to once a week. My other dog was fine and had a normal bowel movement. Does anyone else on here feed herring? Thanks.