Cooking & Baking

and I've been warned by a vet that too much uric acid causes kidney problems, to which cats are particularly prone. Both of my Mom's cats died of kidney failure. And there's other concerns besides ...

https://www.cathealth.com/cat-care/nutrition/2246-ethoxyquin-mercury-and-pcbs-is-feeding-fish-safe-for-cats
https://mypetnutritionist.com/post/the-problem-with-purines/ (some dog breeds have similar problems)

Cheaper brands of cat food often include some form or another of fish-byproducts or fish meal in the ingredients. Sometimes you have to read well down the list on the label to spot it. The silver scales of many species of fish (including sardines) are rich in guanine, and indeed crystalline guanine looks very reminiscent of fish scales.