Rabbit Nutrition

by Kathryn Smith

Many rabbit care websites tell us what percentages to look for in fiber, protein, and fat content of purchased food. We hear that carbohydrates are bad. Too much protein and fat is bad. Not enough fiber is bad. But how many of us understand the role of these nutritional elements? I certainly didn’t before I started working on this article. Frances Harcourt-Brown’s Textbook of Rabbit Medicine* is an excellent resource for more detail about diet and nutrition. What follows is a summary of what I have learned while researching this article.

As you will notice, there is no “one size fits all” formula for nutrition – and no food (or water) source is 100% risk free.

Fiber is considered the most important component of a rabbit’s diet. While hay should be the primary source of fiber, when choosing a commercial food it is also important to choose one with high crude fiber content (at least 16%). Although crude fiber percent understates the amount of dietary fiber in most commercial food, it is the value that is required (by law) to be reported. There are two main types of fiber. Indigestible fiber comes mainly from the long strands found in grass or grass-based hay. It keeps the GI tract moving, helps create normal dental wear, stimulates the appetite, and encourages the eating of cecotrophs (partially digested foods that are passed from the bunny – they have a grape-like appearance – and then reingested). A diet too low in indigestible fiber can result in GI and dental problems. However, a diet too high in indigestible fiber can result in malnutrition. Fermentable (digestible) fiber comes from smaller particles of hay and commercial food and fresh produce. Digestible fiber provides nutrition, helps maintain the balance of cecal flora, and contributes to healthy, firm-consistency cecotrophs. Harcourt-Brown suggests feeding fresh grass (if not chemically treated) because it contains both indigestible and fermentable fiber. In areas where you frequently see raccoons, skunks, and other wildlife, there is a greater risk of grass being contaminated with parasites. If you pick fresh grass for your rabbits, thorough rinsing can help reduce – but not totally eliminate – that risk.

Protein is required for healthy bone, muscle, and fur growth. Cecotrophs, also known as cecal pellets, provide an important source of protein. However, protein is required for proper functioning of cecal bacteria, so finding the proper balance is important. Too much protein can strain the kidneys. It can cause overproduction of cecal pellets, reduce your rabbit’s interest in ingesting cecotrophs, and/or upset the balance of bacteria in the cecum. Excess protein can also increase ammonia production and excretion. If you notice urine having a stronger ammonia smell, check the protein content of your commercial food. Insufficient protein can result in poor tissue regeneration after an injury. Your rabbit’s body may also “steal” protein from muscle to grow fur. If your rabbit’s coat begins to look unhealthy, check the protein content in the commercial food you are giving (or, if not feeding food pellets, consider adding a small amount to his diet). Commercial foods should contain 14%-16% protein for most healthy adult short-haired rabbits. Angoras and other long-haired or thickcoated breeds may require higher levels of protein. Growing rabbits require more protein than adults because bone, muscle, and other tissue are still developing. Sick rabbits may need higher levels of protein to support their immune system.

Carbohydrates are an important energy source and should not be eliminated completely from your rabbit’s diet. Carbohydrates include natural sugars (found in fruit) and starches (found in seeds, grains, and commercial food). As with other nutrients, the key is finding the correct balance for the individual rabbit at his present stage of life. A diet too high in carbohydrates can lead to weight gain (if converted to fat) and/or a bacterial imbalance in the GI tract. However, a diet too low in carbohydrates may cause your rabbit to move less to conserve energy. Sick rabbits also may require more energy to support full recovery. Younger rabbits require more carbohydrates. However, since a young rabbit’s GI system is more precariously balanced, fruit and grain should be strictly limited. Commercial food is usually recommended for growing rabbits. According to Harcourt-Brown, recent studies show that adult rabbits digest starch more efficiently than young rabbits, explaining why some rabbits seem to tolerate the occasional starchy treat. Fats Like carbohydrates, the amount of fat in your rabbit’s diet should be limited but not eliminated. Look for commercial food that contains 2%-3% fat. If your rabbit does not eat commercial food, other sources of fats include grains, nuts, and vegetable oils.

Vitamins help regulate metabolism, release energy from food, assist tissue development, and act as antioxidants. Most commercial food producers do their best to provide the proper balance of vitamins and minerals for domestic rabbits. There is no one brand or formulation that is the best choice for all rabbits, and in a multi-rabbit household, you may need to buy more than one type of commercial food. Vitamin A is important for vision, bone development, and combating infection. Too much Vitamin A can cause neurological and skin damage. B-complex vitamins are found in cecotrophs and play a key role in many metabolic processes. B-vitamin injections are occasionally prescribed to help boost the appetite of an anorexic rabbit. Vitamin C is required to maintain and repair connective tissue. Hartcourt-Brown states that there is evidence that a rabbit’s Vitamin C requirements increase during periods of high stress. Vitamin D plays an important role in metabolism of calcium and phosphorus. Vitamin D is rare in food. Hay that is slowly sun-dried (as opposed to hay that is rapidly cured) contains vitamin D, as do dry autumn leaves (which rabbits allowed to play outdoors seem to prefer over other vegetation), and in commercial (pelletted or extruded) foods.

In Textbook of Rabbit Medicine, Harcourt-Brown hypothesizes that “Vitamin D deficiency may be a contributory factor in the development of dental disease.” Since direct exposure to sunlight plays a key role in proper synthesis of Vitamin D, this may help explain why so many house rabbits seem to have dental issues. Since excess Vitamin D can cause calcium deposits in tissues such as joints and kidneys, Vitamin D supplements should be used with extreme caution (and only under veterinary supervision). Vitamin E is a natural antioxidant, helping to prevent widespread tissue damage. Young grass is an excellent source of Vitamin E. Vitamin K, found in cecotrophs, helps blood clot properly. Other important nutritional considerations involve calcium, the calcium-phosphorous ratio, and magnesium. For more information on those elements, please look to the books cited for this article. Rabbits have a unique and delicate digestive system, so it is important to make sure that what they eat is affecting them in a positive way. They are members of our families and loving companions and we want them to live long, healthy lives.