Dietary therapy plays such an integral role in the management of gastrointestinal (GI) diseases that it constitutes a part of the therapeutic plan in virtually every such case. Diet can be part of the diagnostic process as well, such as using an elimination diet in a dietary trial. It is beyond the scope of this discussion to address each disease of the GI system and the recommended diagnostic and therapeutic approach for each.
Dietary therapy plays such an integral role in the management of gastrointestinal (GI) diseases that it constitutes a part of the therapeutic plan in virtually every such case. Diet can be part of the diagnostic process as well, such as using an elimination diet in a dietary trial. It is beyond the scope of this discussion to address each disease of the GI system and the recommended diagnostic and therapeutic approach for each. Instead, we will consider methods for obtaining an in-depth nutritional assessment of each patient and developing an individualized nutritional plan for dogs and cats with different categories of GI disease to optimize the success (and avoid common pitfalls) of nutritional therapy.
The Circle of Nutrition
Animal Factors-consider the patient's signalment, lifestage, current body weight and body condition (as well as any recent changes in weight and BCS) physical exam findings, health, appetite, activity level and the environment. A detailed history of gastrointestinal signs, and laboratory results should be included help to localize the area and extent of GI tract affected. (see table 1).
Table 1 Anatomic Localization - Small Bowel vs. Large Bowel Diarrhea
Determine whether the current diet is home prepared or commercial product(s) including the form (moist semi moist or dry). If home prepared, obtain the recipe and amounts eaten. If the patient is fed a commercial food, examine the quality and availability of the diet. The food should be made by a reputable manufacturer, have a nutritional adequacy statement that it has undergone animal feeding trials for adult maintenance, have a nutrient profile matching the needs of this specific pet, and provide adequate dietary protein. Ask how long the patient has eaten its current diet. With GI disease, owners will often have attempted several diet changes on their own, or on the advice of staff from a pet food specialty store, their neighbour or the internet. Asking only about the current diet can be misleading and not reflective of usual intake. If the patient has undergone recent or frequent changes in foods, ask specifically about each diet used, (brand, flavor/type) as well as the response to each diet, and reason for change. Make sure to ask about type and amounts of additional dietary components, treats and supplements.
Feeding Management Factors
Ask how the food is offered and how often. Is it measured and how? Is intake observed? The availability becomes especially important in multi-pet households.
Once this assessment is complete, either a diagnostic plan is in place, or hopefully a diagnosis is pending. Sometimes, however the decision is made to perform a diet trial in lieu of diagnostics, as part of the diagnostics or as part of the therapeutic plan. Use your knowledge of localization of the disease, and the nutrient profile of the diet to formulation the nutritional plan for the patient. The nutritional goals should be to 1) meet the nutrient requirements for species, and lifestage with a complete and balanced diet 2) prevent or correct protein calorie malnutrition 3) improve or resolve clinical signs 5) correct any underlying nutrient deficiencies (ex. cobalamin in IBD) 6) potential for targeted nutrient to modulate the disease process.
There are 4 major diet categories used in the management of gastrointestinal diseases. These include:
1. Highly digestible, Low residue- This represents the therapeutic "enteric" diets with high quality, highly digestible protein, low fiber, with moderate to lower fat levels (Examples: Hill's i/d®, PVD EN, Eukanuba Low residue, Royal Canin Sensitive formula)
2. Novel Protein- These diets are meant to offer a single, novel source of dietary protein often with a single source of carbohydrate. Use of these requires a thorough, lifelong diet history in order to determine suitability. (Examples: IVD limited antigen, Hill's d/d, PVD LA, Eukanuba KO).
3. Hydrolyzed protein diets- These diets contain proteins as short peptides, which are more easily absorbed than intact proteins and are theoretically "hypoallergenic" as their small size means they go undetected by the immune system. These diets are also formulated with purified starches as the carbohydrate source. They have the added benefit of also being highly digestible (low residue) even in the presence of significant GI disease (Examples: Hill's z/d, PVD HA and Royal Canine Hypoallergenic HP).
4. Fiber enhanced- These diets have increased levels of fiber(s) (either high insoluble fiber a mix of soluble and insoluble fiber). Not all fibers, and not all high fiber diets are alike, and it is important to have an understanding of these differences for successful management of the most severe colonic diseases
When the presenting signs or disease process localizes to the small bowel, it is more likely that a highly digestible, novel protein or hydrolyzed diet will be successful. Select the category based on clinical signs or diagnostic results, in addition to the diet history. Have any of these categories been utilized? What was the degree of success? The plan should be to select from the diet category and use that diet exclusively if possible to avoid confounding variables in treatment. Most patients will show responsiveness within 2 weeks of a diet trial. If no success, then select a diet from a different category, and proceed again.
If food allergies are suspected, an elimination trial is in order. Currently the gold standard is to have the owner home cook a diet made of a novel protein source. This is becoming increasingly challenging. To select the novel protein, you must have a history of all diets the pet has been exposed to. Many pets have been exposed to multiple brands, and many treats and human foods. Many commercial products are made of multiple protein sources, and formulation may change over time. Often the owner cannot provide an accurate diet recall, or declines to cook because of concerns about cost and labor. In the absence of an accurate diet history, a hydrolyzed diet would be preferable for the elimination diet trial.
If the large bowel is the suspected site of disease, either a fiber enhanced or a low residue diet would be an appropriate first choice. Colitis is variable in its causes and responsiveness to dietary fiber. It may be worthwhile trying alternate sources and types of fiber. The type of diet that is most effective will depend on the dog or cat's acceptance of the diet, the dietary needs, and the disease process. Pumpkin is a commonly recommended supplement as a source of fiber. Pumpkin does contain fiber, primarily soluble fiber, however the quantity required to supply a significant dose makes it unrealistic as a dietary fiber supplement: www.nal.usda.gov/fnic/foodcomp/search/
Based on the USDA nutrient database, the fiber content of pumpkin is 0.4 gms total fiber per tablespoon, 7 gms per cup of canned pumpkin.
When making a nutritional plan, estimate the energy requirements of the patient, then determine daily protein requirements, protein ~2 gms/lb ideal body weight for cats and ~ 1 gm/lb ideal BW for dogs. Select the diet from the category that most suits the needs of the individual patient. The diet should be palatable and acceptable to the client and patient. Because we feed to meet the energy requirements of the patient, the best way to compare diets is to look at the nutrient content on an energy basis (example: gms fat/ 100 kcal) to assure the diet is providing the remaining nutrients of concern at an adequate level. Refer to therapeutic product guides or online information or the Ohio State Nutrition Support Service website: http://vet.osu.edu/nssvet for diet table comparisons
Veterinary foods often are sold as containing "high" or "low" levels of some nutrients. Currently, no generally accepted definition of these terms exists. Buffington's definitions, many extrapolated from human nutrition, follow:
Ranges for "high" and "low" nutrient densities in pet foods
Other Nutrients of Concern
Vitamins and Minerals
Vitamin and mineral requirements must be replete. There have been reports of failure to respond to therapy in cats with GI disease and cobalamin (Vitamin B12) deficiencies. They responded once Vitamin B12 was supplemented. With chronic losses, vitamin and mineral deficiencies can occur and may require parenteral supplementation until GI function can be restored.
Future research is needed to further evaluate the efficacy of nutraceuticals and dietary supplements. Nutrients such as omega-3 fatty acids and pre- and probiotics may play a role in modifying the disease processes (immune dysfunction, inflammation) at the cellular level.
Making a Nutritional Recommendation
The dietary and medical history will be valuable tools to help develop the therapeutic plan. Knowledge of previous exposure will help determine the likelihood of success in trying a commercially available novel protein diet, as well as give information and indications of client likelihood for compliance. Use the interval between episodic outbreaks of clinical signs and design the diet trial to be longer than that interval in order to evaluate the success of therapy.
• Feeding Factors- In order to avoid causing food aversions, care should be taken not to make sudden changes in diet or to make changes when the pet is feeling ill. Food aversion is quite strong, so introduce new foods gradually and consider optimizing the timing.