As you know, my habit when I don't have enough info to figure that I can provide a definitive answer to a question or come to question what I had accepted is to ask an expert. Below is from Dr. Tom Willard whose doctorate is in animal nutrition. I learned a LOT from this and hope that you also will. [Begin Dr. Willard post:] Kidney Disease and Diet This is not intended to be a complete review paper regarding kidney disease in carnivores or ferrets but only to bring up several points which are know about the kidney of different species and to make recommendations regarding the diet of carnivores. I would have to say in my 30 years in the pet food industry and over 10 years in working almost exclusively with ferrets in both nutrition and research, that renal failure - cause and effect - is possibly the most misunderstood and mistreated disease in companion carnivore pets. First, we need to define chronic renal failure. According to Dr Gregory Reinhart, PhD and Director of Strategic Research, R&D, The Iams Co., it is the sum effect of a wide range of diseases that results in loss of 75% or more of the functional parenchyma of both kidneys. In chronic renal failure, this loss of function is progressive and irreversible. Further, it is associated with a gradual decline in glomerular filtration rate plus an accumulation of protein metabolic byproducts such as BUN and creatinine. Increased severity of histological lesions and development or worsening of clinical signs (pg 395)_. Dr Delmar R. Finco, DVM, PhD, DACVIM Professor in the Dept. of Physiology and Pharmacology Medicine, U. of GA has conducted extensive research on both dogs and cats regarding the influence of protein one renal failure over the past 20 years. In the 1998 Iams Nutrition Symposium Proceedings_ (pg 413), Dr Finco presents a paper on the Influence of Protein and Energy in Cats with Renal Failure, states in his summary: "It is concluded that restricting protein in cats with chronic renal dysfunction for renoprotective purposes is questionable, unless more convincing evidence of harmful effects is provided". He goes on to elaborate in his presentation that progressive renal failure is a common cause of death in cats so slowing its progress will prolong the life and add to the comfort of the animal. The same would obviously be true for ferrets. But Dr Finco goes on to state, "contrary to a previous study, results did not demonstrate adverse effects of protein ingestion on glomerular mesangial matrix accumulation, even when amounts consumed were greater that previously shown to be injurious". There have been studies on dogs that have shown that there is no relationship between protein intake and progression of chronic kidney disease seen in rats, according to Dr Gregory Reinhart of The Iams Company_. Dr Reinhart goes on to state that there is no evidence that feeding moderate protein diets to either dogs or cats relative to severely protein restricted diets contribute to progression of chronic renal failure, the rational for excessive protein restriction is even more questionable in these species. Most of the misinformation regarding the benefits of feeding protein restricted diets has come from a poorly designed study over 35 years ago pertaining to laboratory rats with kidney disease. Not until Dr Finco began his research on dogs in the late '70's and early '80's and later on cats, using the remnant kidney technique, which he developed, did factual information become available on carnivores regarding the effect of dietary protein levels on kidney disease. In an uncontrolled and unreported research study, which we conducted during the mid '90's on ferrets, we demonstrated a positive effect on eight-week-old ferret kits who had suffered kidney damage and exhibited extremely elevated BUN levels. We fed our current Totally Ferret diet of 37% protein and 23% fat to all nine kits and 4 of the 5 recovered whereas the 4 kits fed a low protein, low fat diet (30% protein, 16% fat) all died. Based on all of the information I have reviewed plus many of our own studies, restricting the protein intake on an obligate carnivore such as a ferret is contraindicated. Not only will the essential amino acids not be available for tissue rebuilding in the damaged kidney, there will be a lack of all of the essential nutrients for immune system rebuilding which will open the animal up to secondary infection. This includes feeding special prescription cat diets designed for kidney dysfunction. As previously stated, this is not a lengthy review article on kidney disease of carnivores in general nor ferrets specifically; it is a presentation of some specific information as sited above regarding dogs and cats. There is little or no direct research information on kidney disease in ferrets which I am aware of so we can only attempt to draws some cross species conclusions. I do however, suggest that any veterinarians diagnosing renal disease in ferrets at least consider that ferrets are a more restrictive carnivore that cats and according to the available research in cats restricting protein is contraindicated for disease symptoms mitigation _. I will be happy to further discuss this with anyone involved in research on ferrets as our company is always interested in advancing the nutritional and healthcare knowledge of the domestic ferret. Thomas R. Willard, PhD President Performance Foods, Inc. [Posted in FML issue 4153]