A ferret is an obligate carnivore, and must eat appropriately for the species to maintain health. Adult ferrets have 34 teeth. Ferrets have a very short intestinal tract; the GI transit time is approximately 3 hours, a time so short that absorption of nutrients is not that efficient. Because of this timeframe, 3 hours is adequate when fasting a ferret before surgery. Transit time in young ferrets can be as short as one hour. Ferrets tend to eat small amounts at frequent intervals. Young ferrets particularly need high-quality diets while they are growing.
Pregnant ferrets will require extra protein (not fat) during gestation. Lactating (nursing) ferrets will require extra caloric intake. Abandoned or orphaned kits may be hand raised with either puppy or kitten milk replacer with cream added to raise the fat content. Ill, anorexic ferrets can develop hepatic lipidosis and hypoglycemia. There are good dietary supplements commercially available for assist-feeding anorexic ferrets. Ferrets with insulinomas, a common problem, should be encouraged to eat every few hours.
Whole prey diets (chicks, mice, and/or rats) are fine for ferrets and are popular in certain parts of the world although not so much in North America. Cat food is often fed to ferrets, but ordinary grocery store cat food is a poor choice for them. Premium dry cat foods or balanced commercial ferret diets are better choices. The ideal ferret diet is high in protein (30-35%) and fat (15-30%), and low in fiber. The protein source should be meat-based, rather than grains. Grain-based diets have been associated with urolithiasis in ferrets. Ferrets fed dog food will not do well. Meat or poultry or their by-products should top the ingredient list of any suitable ferret food. A diet in which the first main ingredient is corn is not a suitable diet for ferrets. The feeding of table scraps should be kept to a minimum. There are several brands of supplemental nutritional products for ferrets that are commercially available. These products are unnecessary in most ferrets. Older ferrets may require less protein than when they were younger.
Fruits and vegetables have little nutritional value for ferrets. An adult ferret needs approximately 43 grams of dry food per kilogram of body weight, and 200-300 calories/kilogram per day. Calcium: phosphorus ratios in ferret diets should be minimally 1:1. Dilated cardiomyopathy (DCM) occurs in ferrets, and although it has not been associated with taurine deficiency, taurine is generally added to ferret diets as is the case with cat food. Commercial ferret diets have vitamins and minerals added in adequate amounts. Water should be made available at all times; most ferrets will prefer a bowl to a sipper bottle. They also like to play with their water. Ferrets tend to not be fond of changes in their diet after they are used to a certain kind. Ferrets imprint by smell on the food they like at a very young age. Most ferrets will be content to eat one brand of commercial diet that they enjoy for their entire lives.
Treats should not consist of more than 10 percent of the daily diet. They love raisins; however, while there is no formal study on ferrets and raisins, there are anecdotal reports of raisin toxicosis in ferrets, so raisins are best avoided. Egg can be a good supplement, as can small amounts of liver or hamburger.