Those who are genetically susceptible to getting cystine uroliths may have a problem. Searches in the FML Archives and FHL Archives will provide details on why those as well as high levels of any of the COLA grouping of amino acids, cystine, ornithine, lysine, and arginine may need to be restricted in those individuals. I trust people to search the archives. The FML Archive address is in the header of each day's digest. There has been a lot of discussion of this topic in past issues of the FML. The problem is that unless you know the health issues of the specific bloodlines you often do not know about this vulnerability being present in an individual until the ferret blocks which can be fatal, especially in the males. We have had such ferrets live happy and long lives on protein restriction, but that is not optimal for individuals who do not have this problem. For those who have it that approach usually prevents death, though a few also need meds. First indication can be difficulty defficating due to the colon being compressed by the stones in the bladder. [Posted in FML 7963]