Nutrition in Small Mammals

A variety of small mammals such as hamsters, guinea pigs, mice, rats, rabbits, and chinchillas are commonly kept as household pets for adults and children alike. These pets have been bred in captivity for years and are ideal for a variety of pet owners because of their small space requirements, quiet nature, ease of handling and relatively simple husbandry requirements. Diet is an important part of the care of these pets and each species should have its own specific nutritional needs met. A rabbit is not a rodent is not a ferret, and so on.

Clean water must be accessible to these pets at all times. Some species, such as chinchillas and gerbils, require less water due physiological adaptations to living in an arid environment, but they still need a ever present water source. A sipper water bottle is the best choice because it cannot be contaminated with bedding, food, feces and urine. Animals unfamiliar with a sipper bottle may have to be trained to use it. It is not necessary to add vitamins to the water for any of these species if the recommended diets are followed. The disadvantages of adding vitamins to the water include; making the water taste disagreeable and promoting bacterial growth. In addition, many vitamins are inactivated shortly after they are exposed to air, water and light which reduces their effectiveness. Although, it is a rare problem, it is possible to overdose a pet on vitamins which can result in disease. Medications should be added to the water only under the advice of your veterinarian.

As a general rule, any changes in your pet’s diet should be made slowly over a period of time to avoid intestinal upsets. If your pet is not in the best of health, or if you are in doubt about changes that should or should not be made as suggested by this article, please consult your veterinarian before proceeding. The dietary recommendations in this article are made for NON-BREEDING, NON-PRODUCTION PETS. If you are involved in a breeding or production program, you may need to make adjustments in the amount and types of foods fed.

And keep in mind, as you tour your local pet store, that they sell products because people buy them. It does not mean that they sell products that are good for the animals. And there are plenty of products sold as bedding, diets, treats, and supplements in pet stores that are not healthy. When you make an appointment, we will discuss the bedding, housing, and diet recommendations in more detail.

Rabbits
Rabbits are perhaps the most commonly kept small mammal (other than cats) in the United States. They are not rodents, but are included in a family called Lagomorphs. They are strict herbivores and have continually growing incisors and molars that are designed to tear and macerate very tough leafy foods. The teeth rub against each other and are worn down by the action of eating. Rabbits require a large percentage of fiber in their diet to maintain normal gastrointestinal motility. Rabbits have a large cecum, which is a blind pouch located at the junction of the small intestine and the large intestine, where the digestible portions of the intestinal contents enter and are broken down by bacteria. Some nutrients are absorbed through the wall of the cecum, but most nutrients are locked up in the bacteria. The rabbit then produces bacteria-rich droppings called cecotropes, which are softer, stickier, greener and have a stronger odor than the regular waste droppings. These cecotropes are eaten directly from the anus as soon as they are produced. The cecotropes are then passed through the digestive tract of the rabbit and nutrients such as vitamins, amino acids and fatty acids are released from the bacteria and absorbed into the rabbit’s body. In this way, rabbits are very efficient at producing their own vitamin, protein and fat supply from food that for some animals, such as ourselves, would be totally useless.

The biggest mistake people make when feeding rabbits is overfeeding high calorie foods such as commercial pellets and grains and underfeeding high fiber foods such as hay and greens. This pattern of feeding can lead to obesity and gastrointestinal disease. The most important part of the house rabbit diet is an unlimited supply of grass hay which provides essential fiber as well as proteins, vitamins, minerals and carbohydrates. In addition, because of the high fiber content of the hay, it is the best preventative for stomach and intestinal problems such as ‘hairballs’ and chronic soft stools making it unnecessary to routinely use hairball laxatives or anti-diarrheal products. Hay should be provided for your pet in a box or hay rack and should always be available. Grass hay is preferred over alfalfa hay because grass hay it is lower in calories and calcium. (Commercial pellets already contain a large portion of alfalfa hay). There are several types of grass hays available such as mixed grass, timothy or oat. Hays vary depending on the area of the country and the time of the year. Sources of hay include pet stores, feed stores and horse barns. If you have several rabbits, it may be beneficial to buy an entire bale of hay as it will be gobbled up quickly! Hay should be stored in a cool, dry area in an open bag to allow for good air circulation. Hay should have a fresh smell. Damp hay can become moldy and should be discarded. Rabbits of any age can be introduced to hay without any special preparation.

Another important part of the house rabbit diet is fresh, leafy greens. These food provide not only fiber, but a variety of vitamins, such as A and C, minerals, proteins, and carbohydrates. Most rabbits really enjoy their greens. The old stories about greens causing ‘diarrhea’ are usually referring to rabbits that have been on a low fiber or high calorie diet, such as a commercial pellet or a high grain diet, that are suddenly introduced to greens. On commercial pellets or grains, the gastrointestinal tract may become a bit sluggish due to the high calorie content and lower fiber content, then a diet high in grass hay and greens. When greens are introduced to these rabbits, the intestinal tract ‘speeds up’ to a more normal rate and some of the bacteria in the cecum may change, resulting in a temporary ‘diarrhea’ which usually stabilizes within a week. For recently weaned rabbits or rabbits that have never been exposed to hay or greens before, first introduce hay to the diet for two weeks and then introduce greens gradually and the transition should go smoothly.

Feed at least three different types of greens daily so that you provide a variety of nutrients. Greens should be washed thoroughly, to remove dangerous pesticides. Uneaten fresh foods should be removed from the cage after 3 to 4 hours to prevent spoilage. The amount to feed is a minimum of 1 heaping cup of greens per day per 4 lbs of body weight. You can double or triple this amount as your pet becomes used to these great foods. Some examples of nutritious greens are: dandelion greens (and flowers), raspberry leaves, kale, mustard greens, escarole, endive, raddichio, collard greens, beet greens, carrot tops, parsley, turnip tops, romaine, Swiss chard, bok choy, mint leaves, cabbage (red and green), etc. Use dark, tough, leafy greens as opposed to light colored thin-leafed greens such as bibb lettuce and iceberg lettuce. Other vegetables and fruits that can be fed in the amount of 1 heaping Tablespoon per 4 lbs body weight daily (total volume of all these foods fed combined) are pea pods (not the peas), carrots, apples, pears, peaches, strawberries, raspberries, blueberries, squash, tomatoes, papayas and mangos. Stay away from starchy and high sugar content foods such as bananas, peas, corn, beans, grapes, white and sweet potatoes. Cereal grains and cereal products can cause digestive upsets due to their high starch content, are high in calories and in general should not be used for the house rabbit. These foods include: bread, cookies, crackers, rolled oats, breakfast cereals and other grain products. Although many people feed these treat foods because their rabbits love them (like candy!) if they are fed in too large an amount, they can create obesity and chronic soft stools. Don’t introduce these ‘candy’ items to the diet and your pet will only know good nutrition and never know about the ‘junk food’ he or she is missing!

Commercial rabbit pellets were originally designed to promote rapid growth, weight gain, and ease of feeding for production rabbits (meat and fur) and laboratory rabbits. They are very efficient at what they are designed to do, but for the house rabbit that is to live out a full life, the unlimited feeding of a commercial pellet may be a problem. Once rabbits are full grown, they don’t need to put on more weight. Feed your pet a commercial pellet that is designed for the maintenance of the adult rabbit, with a fiber content of 18% or higher, a protein content at around 13-14% and fat content at no more than 3%. Once a young bunny has reached its adult size (4-8 months depending on the breed) we recommend cutting back the pellets to 1/8-1/4 cup per 5 lbs body weight per day as a MAXIMUM. Remember, there is always hay available so your pet will never go hungry. Pellets should be bought in amounts that will be used within 3 months and kept in a closed container in a cool dry place to prevent spoilage. Do not use pellet mixes that contain grains and seeds along with the pellets. The addition of the grains and seeds only add to the calorie and fat content which can result in obesity, liver and intestinal disease. Some rabbits that are obese and have difficulty losing weight on pellets may have to have them removed from the diet altogether, but this should be done only under your veterinarian’s supervision.

Additional supplements are not needed for rabbits on a diet that is rich in hay, greens and limited pellets.

Guinea Pigs
Guinea pigs, rats, mice, hamsters, gerbils, and chinchillas are all rodents, but they have some distinct differences in their dietary requirements due to the diverse habitats where they originate. Guinea pigs are herbivores and require a similar diet as rabbits with plenty of grass hay and greens and limited commercial pellets. They have continuously growing incisors and molars which wear down, as in the rabbit, with the normal action of eating. Guinea pigs also produce nutrient rich cecotropes in a similar manner as the rabbit which they eat directly from the anal area. Guinea pigs should have unlimited grass hay for the same reason as rabbits. Dark leafy greens are particularly important to guinea pigs due to their requirement for an external source of vitamin C. Other rodents, rabbits and ferrets produce their own vitamin C inside their bodies. Dark, leafy greens are very high in vitamin C, for instance a cup of fresh kale contains approximately 250mg of vitamin C compared to a cup of oranges (without the peel) which contains only 50mg of C. The minimum daily requirement for vitamin C in the guinea pig is 10-30 mg per day. Guinea pigs can easily get this amount and more with the feeding of 1/2 to 1 cup of fresh leafy greens (as in the list for the rabbit), daily. Some particularly high vitamin C foods are kale, dandelion greens, parsley, collard, green peppers and mustard greens. Supplementing vitamin C in the water is not very effective due the rapid breakdown of the vitamin when it is exposed to light and heat and the fact that some vitamin C products have a very bitter taste. Feeding fruits and other vegetables in small amounts as described for the rabbit is also acceptable.

Commercial guinea pig pellets can be fed in limited quantities. Guinea pigs can become overweight on unlimited pellet feeding, particularly if they are not allowed to exercise daily. Feed 1/8 cup pellets per 2 lb guinea pig daily. Although guinea pig pellets have vitamin C added, you should not depend on them to provide the full daily amount. Guinea pig pellets must be used within 90 days of the day they were produced to guarantee sufficient amounts of vitamin C. In many situations, bags of pellets have been sitting on the shelf for longer than 3 months and the vitamin C content is drastically reduced due to breakdown by contact with air, moisture and high environmental temperatures. Scurvy, a disease caused by vitamin C deficiency, is still one of the most common diseases seen in the pet guinea pig fed a strictly commercial pelleted diet. Rabbit pellets should not be substituted for guinea pig pellets because they may contain excessive levels of vitamin D which can be toxic to guinea pigs. Do not feed cereal grains or sugary foods to guinea pigs for the same reasons as in the rabbit.

Guinea pigs are notorious for playing with their water bottles and spilling a great deal of water into the cage. The bottle may have to be refilled frequently and the bedding underneath it changed daily to prevent mold from growing.

Chinchillas
Chinchillas have a diet similar to rabbits. They are herbivores with continually growing teeth as in the rabbit and guinea pig. They originally came from a dry, cold mountainous area. Chinchillas appear to have a diet that depends a great deal on dry grasses and other plant material. Chinchillas should be provided with unlimited grass hay as described for the rabbit because the fiber is critically important to proper digestion and the tough hay strands may be helpful in keeping the teeth worn properly. They can also be offered greens as described for the rabbit, but they will tend to eat less, and offering one half to one cup daily is sufficient. Commercial chinchilla pellets can be fed in the amount of 1/8 cup daily for an adult chinchilla. The pellets should contain approximately 16 to 20% protein, 18% fiber, and about 2 – 5% fat. Chinchillas can also be offered small amounts of dried fruits and nuts not to exceed 1 teaspoon total volume per day. Chinchillas rarely have a problem with obesity and these ‘treat’ foods appear to be greatly relished.

Rats, Mice and Hamsters
Rats, mice, and hamsters have similar dietary requirements. They all eat primarily plant material but rats, mice and particularly hamsters are also know to eat some meat products and are considered omnivorous. All of these species have continually growing incisors which wear down as described for the rabbit. The basic diet for this group should consist of a good quality rodent chow or lab block. Rodent chows should have a minimum of 16% protein and 4-5% fat content. These dry foods can be left in the cage at all times in a bowl or hanging feeder to be consumed as needed. Very young, recently weaned animals may have a problem gnawing on the hard pellets and it will be necessary to break them into smaller pieces or soften them for a few weeks until the pet is more mature. Pelleted food should be purchased in amounts that will be used in three months to prevent spoilage. Good quality rodent chows are considered to be fairly complete diets for this group.

Other foods can be fed in addition to the commercial pellets but should not constitute more that 10% of the total diet. Fruit and leafy greens as described for the rabbits, guinea pigs and chinchillas can be offered. Remove any uneaten fresh foods within 3 to 4 hours to prevent spoilage. All of these species love grains, nuts and seeds, but these foods should be offered in very small quantities because of their high fat content. If these ‘treat’ foods are given free choice, the pet will eat them exclusively, not eat the balanced pellets and develop nutritional disease such as obesity. A few nuts or seeds daily given as a special treat is acceptable. Meat and cheese in small amounts may be offered to mice, rats and hamsters. These foods spoil rapidly and should be removed from the cage within one hour if not eaten.

Conclusion
Feeding your pet will take some thought and preparation, but once a routine is established it should be easy to accomplish. Good nutrition is the basis for a strong body. Feeding your pet in a healthy manner will help to prevent many potential disease problems down the road.

Visit your veterinarian with your pet regularly not only for health checkups but to stay informed of current information in the ever evolving field of small mammal husbandry and care. We recommend annual check ups for your pet.

Copyright 2000 – 2008 by Susan Brown, DVM. Used with permission. All rights reserved