That's right, you incredibly bright person, you. It means you can feed a low protein diet and make cystine stones, or feed a higher protein diet and not make stones; ultimately the deciding factor is the concentration of cystine in the urine, which means it all centers around hydration. Because kibble is a dry product with a maximum of 10% moisture, and the number one treatment for cystinuria is a high intake of water, eating a dry kibbled diet can contribute to dehydration. You could be eating a product with only 25% protein, but if it sucks water out of your bloodstream to rehydrate the kibble, you could drop the specific gravity of the urine enough to cause a precipitation cascade, building cystine stones. Meat, on the other hand, is between 60-75% water, so even though it has a higher protein level, the demand for water is lower, so there is less of a likelihood that a cystine precipitation cascade will result. In all fairness, I should point out the most dangerous food of all would be high protein kibbles because you get the double whammy of high protein and dry food. However, using the word "dangerous" to describe high protein kibbles is only valid when used with ferrets diagnosed with cystinuria; it is not a danger in normal, healthy ferrets--not all. So, why do I know cystinuria is not a widespread genetic trait in ferrets? Because it is probably either an autosomal recessive trait requiring two copies of the bad gene, or it is X-linked, meaning a lot of males would show the disease in a very high ratio over females. While most of these cases are inherited, it is possible a chance mutation could cause it in an individual male, not having a second X-chromosome to resolve the problem. In any case, if this problem were in the general ferret population, you wouldnt be hearing about a couple of cases, even ten of them; they would be as common as adrenal disease or insulinoma. Cystinuria is common problem in dogs because it is widespread throughout the gene pool of 60 different breeds. Remember, it is NOT protein that causes the problem; its a function of acidity and concentration of cystine in the urine. ANY ferret with cystinuria would form stones if they were sufficiently dehydrated. Think of how many albino ferrets there are, and that trait inherits exactly like the most common form of cystinuria. If cystinuria were in the general population, you would have an incidence of the disease that would equal or exceed the diseases we are familiar with today. We don't, so it cannot be in the general population. The only possible explanation for the small number of reports is that whatever is driving this inherited disease, autosomal recessive or X-linked recessive, it remains relatively isolated from the general population. As I said, it is not a problem that worries me in the slightest. You treat the sick ferrets without punishing the rest. Now, to sweeten the pot, I made a long-distance call this morning to an expert in cystinuria to ask for some tips in small carnivores. The person was very interested in any cases in ferrets because they are so unusual. I read my previous remarks over the phone, and after a couple of corrections that clarified what I was trying to say, the post past their approval. I specifically asked what steps ferret owners, IN CONJUNCTION WITH A LICENCED VETERINARIAN, could do for this problem. The following hints were suggested: 1) Try to increase the animal's water intake by feeding liquid food, soups, and broths; your goal is to double the ferret's urine volume. Do not feed dry foods, such as kibble, unless they have been hydrated. If your ferret is well hydrated, the treatment of choice, they will probably not form cystine stones, especially if the urine is slightly alkaline (see #2). If your ferret has cystine stones, increasing the water intake can even dissolve them. If you cannot increase the fluid intake orally, it is possible to give fluids subcutaneously once or twice a day. Make sure your vet monitors the ferret's electrolytes and urine specific gravity. 2) You can add small amounts of baking soda (sodium bicarbonate), or better still, potassium citrate to the food to make the urine less acidic (see #3). Your vet needs to monitor urine acidity--you want to get it close to pH 7.5; any more alkaline and you cause other types of stones to form. 3. Do not allow your ferret extra salt; eliminating extra sodium might increase cystinuria, elevating the risk of stone formation. 4. Your vet can prescribe drugs that bind to cystine, such as Tioproin or Penicillamine, making it up to 50 times more soluble in urine. Talk to your vet- -if they care for dogs, they should know these drugs are and how to give them. 5. Signs and symptoms of cystinuria result from the presence of cystine stones. If your ferret does not have cystine stones in the first few years of life, it probably never will. This is a recessive genetic trait that results in a reabsorption problem in the tubules of the kidneys. There is no cure and you have it all your life, birth to death. 6. It is not a good idea to limit the amount of protein or cystine in the diet unless all other methods of controlling the formation of stones fail. In cystinuria, not only is cystine spilling into the urine, but also, so are three other amino acids. Additionally, because the disease affects the transport of cystine across cell membranes, not only is cystine spilled into urine, but it also means there is impaired absorption of cystine through the intestines. Reducing protein in dogs is a useful treatment, but dogs are carnivorous omnivores, while ferrets are primary, obligate carnivores, and the reduction of cystine, a precursor of taurine, may have unforeseen redults. Regulating hydration and urine pH is a far better course of treatment, and unless it fails, protein reduction should be avoided. 7. Cystinuria is relatively unknown in ferrets, but the causes and treatments are the same in ALL species that have shown the disease (the Merck Veterinary Manual details the same basic treatment for all species, and it matches the treatment for humans). Nonetheless, all procedures should be carefully monitored by your veterinarian in cause ferrets have a physiological quirk that requires modification of the treatment. As I said, it is a disease that cannot be widespread in ferrets, so there is absolutely no reason to worry about foods with increased levels of protein UNLESS your ferret shows symptoms of stones. In that case, see a vet immediately, and if the stones are cystine, THEN you can worry about treatment. There is NO REASON to punish the vast majority of ferrets because of the illness of a few. Bob C [log in to unmask] "In that part of the West where Yap Yap the Prairie Dog lives is a relative called the Blackfooted Ferret who looks like a large Weasel. He is about the size of Billy Mink, but instead of the rich dark brown of Billy's coat his coat is a creamy yellow. His feet are black and so is the tip of his tail. His face is whitish with a dark band across the eyes. He is most frequently found in Prairie dog towns and lives largely on Yap Yap and his friends. His ways are those of Shadow and his cousins. There is no one Yap Yap fears quite as much." Thornton W. Burgess 1920 The Burgess Animal Book for Children. [Posted in FML issue 4787]