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Veterinarian Technician June 2005 (Vol 26, No 6)

Gastrointestinal Problems in Rabbits

by Ed Robinson, AS, BA

    Rabbits are being seen more frequently in small animal practices, and with these patients comes an array of gastrointestinal (GI) problems. Technicians should become familiar with the latest techniques for treating these types of conditions, which may not be common knowledge in many practices.

    The Digestive System

    The digestive system of rabbits begins with the teeth, which are designed for chewing a high-fiber diet. This type of diet helps keep the rabbit's continuously growing teeth ground down. If the teeth are maloccluded (i.e., do not meet properly), overgrowth or abnormal sharpening can occur.1

    Rabbits are herbivorous hindgut fermenters (i.e., in these animals, the anaerobic digestion of food by microbes occurs in the cecum). The stomach is used primarily as a storage vessel and is almost always full, even if the rabbit has not eaten recently. The gastric fluid in healthy rabbits has a pH of 1.5 to 2.2, which essentially provides a sterile environment in the stomach and small intestine. A young, nursing rabbit maintains a higher pH of 5 to 6.5 to allow colonization of normal bacterial flora in the colon.2

    Fiber moves rapidly through the small intestine. Digestible nutrients are separated from the coarse fiber and form a suspension with smaller-particle nutrients on top and heavier nutrients on the bottom. These nutrients pass into the haustra of the proximal colon.3 The proximal colon allows the coarse fiber to pass to the distal colon, while the haustra use reverse peristalsis to push the nutrients back into the cecum for fermentation and concentration of nutrients (e.g., protein, volatile fatty acids, amino acids). The coarse fiber is eliminated through the colon in fecal balls, while the digestible nutrients are processed by the cecum. The rabbit's small size and high metabolism help in this process. The hindgut digests starches and fiber, and carbohydrates and nitrogenous materials are mixed with a cell mucin (mucus) product to form cecotrophs.

    Cecotrophs

    Rabbits produce two types of feces:

    • Fecal balls — Used to excrete waste products; these are the feces typically seen by clients and in the clinic.
    • Cecotrophs — Soft masses of nutrients produced in the hindgut and passed through the colon3; often called night or soft feces.

    Rabbits ingest cecotrophs as they are excreted from the rectum. Because cecotrophs have twice the protein and half the fiber found in fecal balls and are high in vitamin content, these feces are an integral part of the rabbit's diet. Ceco­trophs are passed as a normal part of the rabbit's circadian rhythm, but owners commonly mistake them for diarrhea. Rabbits must have access to the cecotrophs to remain healthy; therefore, wire-bottom cages should be discouraged.a

    Nutrition

    Because the rabbit's GI system — from teeth to colon — requires large amounts of fiber for proper function, nutrition is one of the most important aspects in client education. The best diet for rabbits is one that is high in fiber and low in carbohydrates. Carbohydrates can increase the pH in the GI system and allow pathogenic bacteria to inhabit the system, causing GI problems.

    Fresh hay such as timothy, Bermuda, or orchard grass, is a major part of a rabbit's diet. Some high-quality hays are available in small packaged quantities for rabbit owners. Fresh greens such as endive, dandelion leaves, parsley, and carrot tops should also be offered. The greens should be introduced one at a time and those that cause diarrhea eliminated from the diet.

    Fresh fruits and carrots used as treats should be given sparingly. The high carbohydrate content in these treats can alter the rabbit's normal intestinal flora, resulting in bacterial enteritis.2 Once rabbits get used to treats, they can become hooked on them to the point that they will stop eating everything else. Therefore, technicians should ensure that owners understand the danger of feeding their pet rabbits too many treats and should dissuade them from doing so.a

    Common Gastrointestinal Disorders

    Trichobezoars

    Trichobezoars, or hairballs, are a common problem in rabbits. They can be not only life threatening because of their ability to cause obstructions but also a sign of other problems.

    The most common cause of trichobezoars is a low-fiber, high-carbohydrate diet. This type of diet decreases GI motility, which leads to dehydration and accumulation of hair, food, and other stomach contents. As motility continues to decrease, the accumulation dehydrates and forms an impaction, which can occur in the stomach and eventually move into the cecum.2

    Signs include anorexia, weight loss, and depression. During physical examination, the stomach feels enlarged and doughy. In the past, typical treatment was the administration of fresh pineapple juice to break up the hairball; however, this treatment has been found to be potentially harmful. Although fresh pineapple juice contains an enzyme that may help break down the hairball, it is also very high in carbohydrates. The high carbohydrate content and the resulting decreased GI motility can cause a drastic change in intestinal pH, leading to pathogenic bacteria buildup in the GI tract. The accumulation of carbohydrates can lead to "hindgut overload" and eventual death if not treated properly.2

    The best treatment for trichobezoars is intravenous or oral fluids to rehydrate the GI system so the hairballs are able to pass through it. Antibiotics that are safe for the rabbit's GI system should also be administered to support normal bacterial flora and eliminate pathogenic bacteria. Motility-enhancing drugs may be given to stimulate GI motility, and antigas compounds can help relieve gas buildup. Finally, one of the most important factors in restoring proper GI function is dietary supplementation (e.g., Critical Care, Oxbow Pet Products, Murdock, NE).2

    Gastric Stasis

    One of the most often diagnosed GI problems in rabbits is gastric stasis. The condition itself is not the primary problem but rather a sign of other issues (e.g., renal disease, improper diet). It is common for rabbits with gastric stasis to be on a low-fiber, high-carbohydrate diet. Signs of gastric stasis include anorexia, lack of feces, depression, and weight loss. Radiographs taken as part of the full workup may be inconclusive or show gas accumulation, but they often can confirm the diagnosis.

    The underlying cause of gastric stasis needs to be addressed. Treatment includes rehydration to prevent obstructions caused by dehydration (e.g., trichobezoars), analgesics (e.g., buprenorphine), GI motility enhancers (e.g., cisapride, metaclopramide), and antigas compounds (e.g., simethicone). Gastric stasis allows pathogenic bacteria to become established in the GI tract; therefore, antibiotics that are safe for the GI tract (e.g., enrofloxacin) should be given. In addition to all other treatments, the rabbit needs to start eating again to ensure that GI motility returns to normal. Often, it is necessary to force-feed the rabbit a high-fiber, low-carbohydrate supplement as mentioned earlier.

    The rabbit should be discharged as soon as it starts eating on its own and is producing feces. Rabbits are very sensitive to stress, and being sent home as soon as possible can help reduce that stress. The owner should continue to administer antibiotics, antigas compounds, and fluids. Force-feeding supplements should continue until the rabbit begins eating its normal amount of food.2

    Enteritis

    Parasitic Enteritis

    The primary cause of parasitic enteritis is infection from one of two parasites, Eimeria spp (Coccidia) or Passalurus ambiguus (pinworms). Coccidia enteritis is uncommon in rabbits. Although many rabbits are carriers of the parasite, most are asymptomatic. Coccidiosis is more common in young rabbits, and these animals are treated easily with trimethoprim-sulfa drugs. Good hygiene can help prevent parasite transmission.

    Pinworm infections are common in pet rabbits. This parasite lives in the cecum and colon but rarely causes clinical disease. Infections can cause parasitic enteritis with signs of failure to gain weight and decreased reproductive efficiency. Treatment with fenbendazole often has mixed results, whereas ivermectin is often ineffective.1

    Bacterial Enteritis

    Bacterial enteritis can be caused by several factors (e.g., stress, antimicrobial therapy, some forms of gastric stasis). Signs can range from soft stool (fecal balls) to profound diarrhea, gastric stasis, and enterotoxemia. As the pathogenic bacteria start to proliferate, normal intestinal flora decrease. Pathogenic bacteria can create endotoxins and cause enterotoxemia, which can lead to coma and death.2

    Signs of enterotoxemia include brown, watery diarrhea, depression, and anorexia. The stool may contain blood and mucus. Enterotoxemia requires quick, aggressive supportive care and treatment.

    Treatment is aimed at eliminating the pathogenic organisms and repopulating the normal bacterial flora of the intestines. In addition, gas produced by the bacteria needs to be eliminated, and the rabbit should be rehydrated and started on a feeding supplement. The overall treatment is similar to that for trichobezoars and gastric stasis.1

    Conclusion

    As rabbits are seen more frequently in small animal clinics, technicians need to be aware of common problems that can affect this species, including GI disorders, and the most current methods of treatment. Technicians also must educate rabbit owners about the importance of proper nutrition; this will help these pets have fewer GI problems and live a healthier life.

    Acknowledgments

    The author thanks Dr. Kathy Clark of Twin City Animal Hospital, Newington, Connecticut, for recommending this topic and sharing her knowledge of rabbits.

    1. Quesenberry KE, Carpenter JW: Ferrets, Rabbits, and Rodents Clinical Medicine and Surgery, ed 2. Philadelphia, WB Saunders, 2004.

    2. Murray MJ: Rabbit gastroenterology. Proc NAVC: 1352-1354, 2005.

    3. Hillyer EV, Quesenberry KE: Ferrets, Rabbits, and Rodents Clinical Medicine and Surgery, ed 1. Philadelphia, WB Saunders, 1997.

    aClark K: Personal communication. Twin City Animal Hospital, Newington, CT, 2005.

    References »

    NEXT: Life Is Sometimes the Pits

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