Thanks mrsD, you have given me a lot to think about.

I has a not dissimilar experience with my first generation cats (Nicky and Pippa) as yours with Sheba. Not knowing any better, I fed them highly processed stuff from cans. They both got untreatable renal failure quite young. I don't know if their food was causative but doubt that it helped. Lesson learned; avoid highly processed foods for both cats and people.

That is interesting about your omega-3 intervention. I eat fresh salmon three or four times a week mainly because it is a healthy food, including (obviously) being a good source of omega-3 fatty acids. I might try Blackberry and Waiwaiaa out on a bit of it, as a treat, and see how they go.

Thanks a lot for your taurine links = the evidence looks convincing to me. I have moderate and annoying tinnitus in one ear and some osteoarthritic pain in one shoulder - I will try it out as a supplement and see what happens.