I was a Persian Cat Breeder, but have since neutered/spayed all of my 40 remaining Persians. I now find that all my older cats (12yrs) are developing kidney problems - one very large kidney and one shrivelled up kidney. I feed them Royal Canin Persian and share one kg. Venison Mince per day amongst all my cats. My vet says that the mince is the culprit, but I feel they are getting so little. What must I do?