Some other tips for you to consider concerning supplemental homemade cat food. I've always been in the habit of cutting away a lot fat whenever I buy any type of meat.
Often times, its more fat than it is meat! If you have no use for the fat then its a waste by-product and likely thrown into the garbage.
Why not view it as a bonus instead of a waste. Do what I started doing a few years ago, cut off the excess fat, chop into bite sized pieces and store in an airtight container in the fridge.
Try it as a treat for your cats first to see if they will eat it. Most cats will and they love anything that differs from their usual fare.
Some people point out the fact that its raw and that cats can get sick on so-called 'raw' food. I say to that, what do you think they are eating when they catch prey? Its a living animal or bird they've caught that can easily carry a virus or some other sickness yet a cats digestive and immune systems are designed to cope with that. Its fat cut off of fresh meat and if you handle and store it properly, it will be safe. Not one of my cats has ever been sick and its a lot safer than some of the stuff I've seen people feeding their cats on the Utube videos; that's just plain scary.
So, don't think of the extra fat on the meats you buy as waste, use it to advantage. Since cats are meat eaters, their systems are used to digesting raw animal fats. I sometimes include a bit of the meat as well. The result, I have very healthy cats with shiny, soft manes of fur. If they have a poor diet at all, its in the bags of cat food I have to purchase for them. The fat and bits of meat at least supplement this for them.
Try for yourself and watch for the results.