I second all the advice you have gotten from SCM. I have a 17 year old in CRF and has been declining for a couple of years now. Like SCM, I am more concerned about her eating, then the phosphorus content as she is extremely picky eater, even when she was young.
I make my own cat food once a month, divide it up into daily feedings and freeze it, taking out the daily amount the day before to thaw in the fridge. I grind whole chickens (I cut off the fatty pieces but leave some skin on as that is the only way cats can get their Vit D, add 5%kidneys/hearts & 5% liver, a bit of iodized salt (for iodine), and raw egg yolks (great vit B). I make about 30-35 lbs at a time (I have 4 cats).
I mix the raw with quality canned (same brands as SCM has stated). I have no problems leaving it out all day for them to munch on.
I had to slowly start mixing raw with their canned, then eventually get to 50-50 and now they will eat plain raw.
Cat maid to:
Jasper, male Ragdoll ?? (approx 10 yrs)
Rose semi feral, a cpietra rescue, female tabby (approx 7 yrs)
Sweet Pea RIP (2004?-2014)
Puddles RIP (1996-2014)
Snowball RIP (1991-2005)
In a cat's eye, all things belong to cats.-English Proverb
“While we are free to choose our actions, we are not free to choose the consequences of our actions.” Stephen R. Covey