I bought this for my four dogs about a month ago. We noticed a difference in my oldest after about a week. She had more energy, was eating better, and wasn't in as much arthritis pain. One of my others suffers from a digestive disease - he's healthy, but has always been on the small side weight-wise. After a month of having this salmon oil on his food, he's gained about 6 pounds. We haven't changed anything else, so I can only assume it's the oil. I'll definitely keep my dogs on this from now on!!