New Ideas in Feeding Ferrets
By Dr. Louise Bauck, DVM
The domestic ferret requires only small quantities of food, so high-quality, premium diets are a reasonable option for ferret owners. However, there’s more to know about ferret nutrition than recommending or feeding a high-quality, premium ferret diet.
If you own these fascinating carnivores, you owe it to yourself – and your pets – to learn more about their dietary requirements. Although we have scant research on the science of pet ferret nutrition, we have some new findings extrapolated from nutritional research about black-footed ferrets in zoos, as well as mink and cats.
Ferret veterinarians are particularly interested in the relationship between diet and common health problems such as obesity, stunting, urinary tract obstructions, trichobezoars (hairballs) and pancreatic cancer, as well as the relationship between taurine and cardiomyopathy (heart disease). Other areas of interest include omega 3 and omega 6 fatty acids and factors that affect oxidation (rancidity).
Free Choice Feeding
Normally, adult ferrets consume 30 to 40 grams (1 to 1-1/2 oz) of a quality dry ration each day. To promote ‘free choice’ feeding, you may leave dry food out alt day. However, ferrets tend to ignore stale food, so don’t put out more than the animals will eat in a single day.
Ready access to food is particularly important to young ferrets. First, baby ferrets may be more likely to nip or bite when hungry. Second, young ferrets can suffer from hypoglycemia (low blood sugar) if deprived of food. Recently weaned ferrets do best on a dry premium ferret food that has been mixed with warm water. To ensure freshness, replace this moistened food several times a day.
It can be a challenge to provide adequate nutrition for pregnant ferrets, which may suffer from complications such as toxemia or small litter size. Rations for pregnant ferrets must contain more than 35% high-quality protein and more than 22% fat.
Extended fasts are not recommended even for surgical patients. Most surgical patients should be fasted for a minimum of four hours but not longer than eight hours.
High Protein Requirements
Ferrets should not be fed like cats: They need higher levels of quality protein, more fat and less fiber than cats do. However, the guaranteed analysis printed on the food bag is not very helpful in determining protein levels in the food. The protein must have high ‘biological value’ and high digestibility, and the amino acid balance must be suitable for an obligate carnivore with a very short digestive tract and a rapid intestinal transit time. Most reference texts suggest that levels of quality protein for non-breeding ferrets should be 34% to 40% on a dry matter basis.
In 1995, investigators at the Toronto Zoo found that the feral diet of the black-footed ferret is approximately 42.5% protein on a dry matter basis – with prairie dogs serving as the primary protein source. Although the domestic ferret originated in Europe, where it certainly did not eat prairie dogs, its original carcass diet probably consisted of similar, but smaller, rodents.
Because ferrets are not plant eaters in nature, the protein in their diets should be derived primarily from animal sources rather than plant sources, such as soy or corn gluten meal. Some experts suggest that excess plant protein in the ferret’s diet can lead to alkaline urine and urinary stone formation. Urolithiasis, seen in North American pet ferrets, is particularly difficult to deal with in male ferrets, which can develop serious obstructions and infections.
Based on this information, the primary or first listed ingredient in a ferret food should be protein with a high biological value, such as chicken or poultry meal. Poultry meals generally cost more than poultry by-product meals, so they are more likely to be used in ‘premium’ diets. Egg also is a high-cost protein ingredient with a very high biological value.
Good-quality poultry meals for ferrets probably should be bone-reduced grades (low ash). This information does not appear on the ingredient list, but may be obtained from the manufacturer. Meals made from poultry byproducts or other byproducts are difficult for consumers to evaluate because their ingredients vary greatly and are not graded or controlled. Sometimes, desirable organ meats, such as liver, are included. In other cases, all useful items have been removed already. The inclusion of heads and feet usually lowers the biological value of protein in byproduct meals.
Unlike minks, ferrets in the wild do not eat fish. In our experience, some ferrets find fish-based diets less palatable. Unless very high in quality, fish meal may be prone to increased rancidity or oxidation problems. However, some ingredients derived from cold water fish contain oils that are high in valuable fatty acids, and sometimes are given as part of a dietary supplement.
It is important to remember that two similar ingredients may be made to look less prominent in an ingredient list if they have been ‘split’. Common examples include herring meal and whitefish meal, or soya meal and soya flour. Ingredients must be listed by weight, so they move farther down the ingredient list when split. This may make it difficult to determine whether fish or soy might be the principal ingredient. Some manufacturers may have good reasons for using two similar ingredients – contact the manufacturer for more information.
According to the investigators at the Toronto Zoo, the apparent requirements for amino acids (relative amounts) in the black-footed ferret are substantially similar to those of other carnivores. For example, arginine deficiency had been reported in ferrets while taurine deficiency has not. Taurine problems have been studied in the cat, but have not been described in the ferret.
Because dilated cardiomyopathy, a heart problem, has been reported in ferrets, some researchers have become interested in the role of taurine in the ferret’s diet. Feline cardiomyopathies sometime respond to taurine supplementation, but this effect apparently has not been seen in the ferret. Taurine generally is present in premium ferret rations, even though it usually is not listed as a separate ingredient.
High Fat Requirements
Ferret owners should pay close attention to the fat content of any ferret ration. Ferrets have high requirements for dietary fat compared with cats or dogs. In fact, levels of up to 30% have been suggested for normal ferrets!
The quality of the fat is a deciding factor in determining whether fat levels are adequate. For the best fatty acid balance, select diets that use high-quality, fat sources. For example, poultry fat is considered to be high in quality with approximately 60% unsaturated fatty acids and 22% linoleic acid. Beef fat has 52% unsaturated fatty acids and only 4% linoleic acid. ‘Animal fat’ is derived from an unspecified source, usually beef or pork.
Fat and oil substances can be broken down into dozens of saturated and unsaturated fatty acids. Unoleic acid is a fatty acid that is sometimes called an omega 6 type. Often, the terms linoleic acid’ and ‘omega 6′ are used synonymously – as are the terms linolenic acid’ and ‘omega 3′. However, the omega 6 and omega 3 families include many different fatty acids.
What is important is the ratio of total omega 6 fatty acids to total omega 3 fatty acids ingested. Many standard carnivore diets have an unbalanced omega 6 to omega 3 ratio – as high as 20-to-l or 30-to-l. First, fat sources used in prepared foods differ in content. Second, the heat of the extrusion process destroys many beneficial fatty acids.
Several manufacturers have devised solutions to the problem of balancing fatty acids. For example, many diets feature poultry fat – which has a naturally good balance of fatty acids – or special fatty acid additives. In addition, several companies offer fatty acid liquid supplements. Other ferret owners can tell you how much their pets adore products such as Dermacare, FerretDerm, Nutriderm, [Ferretone, Linatone, etc.]. I let my ferret lick a few drops right from the bottle as a treat.
There’s another good reason to pay attention to fat: The sources of fat and their relative amounts affect the food’s shelf stability. Rancidity (oxidation) of fats is an ever-present problem in commercial ferret diets because they contain higher levels of fat than canine or feline diets. Thus, preservatives of some kind are recommended. Ascorbic acid and tocopherols (vitamin E) may not be sufficient to preserve the food if it is stored for a prolonged period or is stored in less-than-ideal conditions.
The use of gas-impermeable materials and low-oxygen packaging techniques as well as storage in cool conditions may significantly preserve the quality of the diet. I recommend storing all ferret foods in the refrigerator after purchase.
Look for an expiration date on any high-quality ferret diet. Buy only what you can use by that date [even if it is on sale!].
Minimal Fiber Requirements
Ferrets probably eat little fiber in the wild, and do not require it in their diets. With shorter digestive tracts than cats, they seem to do better on diets containing fewer carbohydrates than are found in most cat or kitten foods. In fact, one reference has suggested that ferrets may be maintained without carbohydrates if sufficient fat is present. Therefore, grains and fiber ingredients should be minimized in good-quality ferret diets.
Pet ferrets can develop trichobezoars (hairballs), but this is not thought to be related to diet or fiber intake. Because ferrets have low fiber requirements, it may not be appropriate to increase cellulose levels in their diets in an attempt to flush out hairballs, as we do with felines. Grooming our ferrets regularly is a much better approach.
Pancreatic problems (endocrine neoplastic disease or cancer) are common in pet ferrets in North America. Although there is no evidence linking these conditions directly with an increase in dietary carbohydrates, it would seem logical to mimic a natural diet as closely as possible. This means less grain and less fiber in the rations. This also means cautioning owners to severely limit candy treats or high sugar items such as fruit juice, cookies, ice cream, chocolate (also likely toxic), and raisins.
Although many ferret rations contain ingredients such as fruit juices to increase palatability, these additives should be present in very small quantities to avoid introducing unneeded sugar into the diet. Sugars are simple carbohydrates and are not part of the ferret’s natural diet.
Controlling a Ferret’s Weight
Ferrets can become obese. Do not try to manage a ferret’s weight by controlling food portions, increasing the diet’s fiber content or decreasing the diet’s fat content. Instead, the best way to manage a ferret’s weight probably is by exercise.
Let’s look at the link between obesity and exercise. Recently, I was involved in an informal study by a ferret food manufacturer to examine the effects of cage-living versus liberty on a ferret’s weight. Over the course of two years, we studied six ferrets at a time, being careful to rotate their housing situations to minimize the effects of seasonal weight loss or gain. (Many authorities believe that some ferrets tend to gain weight in the fall.)
For the cage-living portion of the trial, we confined six ferrets, in pairs, in three commonly used commercial cages over a period of approximately six months. Although they were allowed out for occasional exercise, the ferrets spent most of their time in the 4′ x 2′ cages. They were fed a high-quality commercial dry ration of 38% protein and 20% fat, offered free-choice in multiple feeding stations. Several of these ferrets experienced obvious weight gains during the trial period.
For the liberty or exercise portion of the trial, we confined the ferrets, one pair at a time, in a room without cages for a six-week trial period. They had access to numerous toys, boxes and tunnels, which were exchanged with novel items each week. They were fed the same ration, still offered freechoice in multiple feeding stations. These ferrets frequently engaged in vigorous play activity, particularly in the morning and evening.
At least 3 of the ferrets were considered to be obese at the start of the exercise portion of the trial. Five of the six ferrets lost significant amounts of body mass and changed markedly in appearance. Although they showed significant weight loss in a short time period, the animals showed no signs of metabolic distress or problems associated with the rapid change.
Apparently it is not necessary to reduce caloric density to cause weight loss in ferrets – even if the diet is relatively high in fat. Increasing the level of exercise may be a safer and more nutritionally sound method for weight control.
Promoting Ferret Food
It is important to remember that feeding kitten food to ferrets is a poor strategy. In my experience, few owners can make a clear distinction on an ongoing basis between a true premium kitten food (sometimes suitable for ferret maintenance if it meets all the criteria discussed in this article) and a ‘regular’ or grocery store kitten food. Rather than take the chance that the owner will switch to a regular kitten food, I simply recommend that all ferret owners feed a high quality ferret food as described here.
At present, we do not have enough research to justify any formal recommendations regarding a special ‘kit’ food for young ferrets. However, experience at one food manufacturer’s holding facility in Canada has suggested that young ferrets achieve excellent growth and health on ferret diets with at least 38% protein and 22% fat.
Canned cat foods and soft-moist cat foods are used less commonly to feed ferrets. First, it is difficult to achieve a sufficiently high caloric density to meet the ferret’s needs when using ordinary canned foods. Second, it is very difficult to keep moist foods fresh – a problem made worse by the fact that ferrets tend to eat small meals throughout the day. Theoretically, these problems can be negated. However, more research is needed on the practicality of using canned diets on an extended basis.
Carcass Diets Versus Commercial Diets
Experts suggest that we mimic the ferret’s natural diet as closely as possible. So why not choose ‘carcass diets’ over commercially prepared diets?
In Europe, it is common to provide pet ferrets a diet consisting of fresh or frozen thawed carcasses, including culled mice, chicks and even fresh road kill. In North America, commercial fur farmers often feed ferrets frozen raw meat and fish diets designed for mink. However, hygiene concerns and the need to purchase large quantities of raw or frozen meat tend to preclude the use of these diets by the average pet owner in the United States. Besides, ferrets raised on dry commercial diets may be reluctant to sample fresh carcasses.
Pet owners will probably have more practical success if they stick with premium-quality dry ferret foods – as long as they remember to critically evaluate the ingredient list and guaranteed analysis information on the packages.
Ferrets are fascinating carnivores that deserve additional research as to their dietary needs. It is my hope that manufacturers will sponsor new research as pet ferrets continue to gain in popularity!
Louise Bauck, BSc, D.V.M., MVSc, is the director of veterinary services for the Hagen Avicultural Research Institute in Montreal, Canada.