Pamela, It seems from the hundreds of ferrets which have passed through here in the past few years that once a ferret is taken off a fish based diet and ut on a chicken based diet-- it doesn't ever want to go back! Now that may just be my interpretation ( human at that) of the ferrets presentation. BUt numbers convince me. The Kaytee does have a fish base as do a few other ferret foods. They are also lower in fat. The chicken based foods ( quality vet grade diets) have as much if not more protein in a chicken base-- they usually have more fat. Fat is a necessary ingredient in the ferret diet. Perhaps this explains why your kid took to the ProPlan over Kaytee. Alicia a shelter Mom [Posted in FML issue 1961]