The Importance of a Digestible Diet For Management of Diarrhea

Anton, a 2.5-year-old, 21-kg (47-lb), intact male standard poodle (FIGURE 1) was presented for a nutrition consultation to a board-certified veterinary nutritionist (EBVS [European Board of Veterinary Specialisation] European Specialist in Veterinary and Comparative Nutrition, DECVCN [diplomate of the European College of Veterinary and Comparative Nutrition]). 

Figure 1. Anton, a 2.5-year-old, 21-kg (47-lb), intact male standard poodle with clinical signs of chronic diarrhea.

Anton had a history of chronic diarrhea (>3 weeks’ duration). The feces appeared soft, sticky, “cow patty–like” (Purina fecal score 6 out of 7; bit.ly/3URgsmq), and were foul-smelling; the frequency of defecation was multiple times a day. The owner reported that the first feces in the morning are typically formed, but later in the day stools are soft as described above (FIGURE 2). The owner stated that Anton has had these problems since puppyhood.

Figure 2. Feces at presentation. They often appear soft, sticky, “cow patty–like” (Purina fecal score 6/7).

The medical history revealed that, as a puppy, Anton was diagnosed and treated for Giardia species infection (treatment with fenbendazole 50 mg/kg once daily). At the same time, he was suspected of having intestinal dysbiosis based on fecal bacterial culture results. Treatments for his chronic diarrhea and intestinal dysbiosis included various dietary trials. Based on the owner’s feedback, a diet consisting of raw meat with cooked potatoes or rice was associated with better but not satisfactory clinical response. On recent physical examination, Anton was bright, alert, and had a body condition score (BCS) of 4/9. No abnormalities were noted. A fecal examination for parasites was negative.

A detailed dietary history revealed that Anton’s current food consists of a mix of commercial dry kibble and canned food (daily amounts: 250 grams dry kibble [lamb, herring, egg, pea, quinoa] and 250 grams canned food [beef, poultry, chicken]). The owner stated that Anton is a very picky eater and often refuses to eat his commercial food. As a result, the owner has been offering various treats during the day to entice Anton to consume his food. These various treats include dried beef jerky, soft beef strips, rawhides, cheese, venison lung, and venison tendon. Anton receives an estimated total of almost 100 grams of these treats per day (650 grams per week).

Upon careful and detailed questioning about a timely association between his regular diet, receiving treats, and the clinical signs of diarrhea, the owner mentioned that Anton appeared to have more frequent episodes of severe diarrhea after receiving soft beef strips and rawhides. Typically, he appeared to have no diarrheic episodes when receiving cheese as a treat.

Presumptive Diagnosis

Based on the clinical history, adverse food reactions, including either food intolerance or food allergy, were initially considered as the main differentials. Previous dietary trials included novel protein diets that were unsuccessful. Because the owner was a veterinarian, owner noncompliance was not considered as a potential cause for dietary trial failure. 

Once food allergy was ruled out as unlikely, food intolerance became the presumptive diagnosis. Additional supportive evidence for food intolerance was that fecal consistency was more normal in the morning and became progressively worse during the day, and chew treats with suspected low protein digestibility were clearly associated with the severity of diarrhea. Furthermore, the amount of these chew treats as a percentage of the total daily food intake was considered high (approximately 15%). A positive clinical response to a homemade diet consisting of raw novel meat sources and potatoes further supported the suspicion that poor digestibility of the provided food as the most likely reason for poor stool consistency.

Therapy and Management

The initial approach to dietary management was to instruct the owner to completely eliminate all commercial chew treats with poor digestibility from Anton’s diet and to provide small amounts of cheese treats instead, which typically have high digestibility and historically were not associated with Anton’s diarrhea. The current food (dry and wet food) was not changed initially. The owner was then instructed to bring Anton in for a follow-up exam in 14 days.

There was a rapid clinical improvement in a few days. Fecal frequency was reduced to once daily and the fecal score was consistently a 2/7 (FIGURE 3).

Figure 3. Picture of feces after owner was instructed to stop feeding treats with poor digestibility.

At the follow-up visit 2 weeks later, the owner reported that Anton was producing solid feces for the first time in years. Long-term follow-up over 4 years revealed that Anton’s stool consistency and frequency remained normal.

Discussion

Clinical signs of chronic diarrhea can be due to multiple causes. Differential diagnoses include infectious causes, such as with parasites or specific bacterial pathogens (e.g., Salmonella, Campylobacter jejuni). True infectious etiologies are considered rare; for example, prevalence of parasites has been reported in just up to 6% of dogs in a recent study evaluating 466 pet dogs.¹ Similarly, the prevalence of C jejuni was 5% (10 out of 185 shelter dogs)² and of Salmonella, 2.5% (60 out of 24 222 pet dogs).³

More frequent causes of chronic diarrhea are chronic enteropathies (CE). CE is an umbrella term that encompasses different subgroups of chronic intestinal disorders that are classified based on treatment response. These include food-responsive, fiber-responsive, immunosuppressant-responsive, and antibiotic-responsive enteropathy.⁴ The pathophysiology of these subgroups is not well understood, but it is likely a combination of intestinal dysbiosis, inflammation, degradation of the protective epithelial mucus layer, and increased intestinal permeability. The severity and extent of these changes vary between individual animals; therefore, no clear biomarkers are available that consistently predict which therapy patients will respond to best. For that reason, a sequential treatment approach is employed, with dietary trials often used as the first step.^5-7 

Various recent studies have shown that the majority of dogs with CE, especially those with milder clinical activity scores and no signs of systemic disease, respond to dietary modulation. Depending on the study, between 55% and 81% of dogs with CE were classified as having food-responsive enteropathy.^8-11 It is likely that food-responsive enteropathies are by themselves an umbrella term, as a variety of diet types have been shown to induce clinical remission in these studies. These include highly digestible gastrointestinal diets, hydrolyzed diets, fiber-enriched diets, and novel protein diets.^4,7,10,12 There is no clear predictor, however, of which diet may work best for any patient. Therefore, it is advised to obtain a detailed dietary history that includes probing owners for possible associations between different diets fed to their pet and the development of clinical signs.

A recent study demonstrated that only a small percentage of clinicians obtain a detailed dietary history for their patients. The same study also showed that if the first dietary trial fails, a significant number of dogs may still respond to a second (66%) or third (44%) dietary trial if a more complete dietary history is obtained in practice.¹³ There are several potential reasons for the high percentage of dogs that are food responsive, and these mechanisms are likely overlapping. Many veterinarians suspect food allergies and use, for example, hydrolyzed protein diets and report high success rates. It is important to note that the prevalence of true food allergies in dogs is suspected to be rather low.¹⁴ Another mechanism by which hydrolyzed protein diets may improve clinical signs is due to their high digestibility, or because some other unidentified food component in the original diet has been eliminated. The base food ingredients in fiber-enriched gastrointestinal diets are typically also highly digestible and, together with the fiber component, can modulate the intestinal microbiota.¹² Fiber-enriched diets have also been shown to lead to clinical improvement in dogs with acute large bowel diarrhea.^15,16

High amounts of treats with poor digestibility (i.e., rawhides) were the main reason for the clinical signs of chronic diarrhea in this case. Higher amounts of protein from low-digestible sources can lead to negative effects on the intestinal microbiota.^17,18 For example, 1 study noted increased amounts of poor digestibility protein sourced from slaughter byproducts led to increases in enterotoxigenic Clostridium perfringens and looser stools.¹⁹ High amounts of proteins were also associated with shifts in the microbiota, a decrease in beneficial short-chain fatty acid–producing bacteria, overgrowth of Escherichia coli and C perfringens, higher fecal pH, and an increased level of metabolites linked with inflammation.^20,21

In Anton’s case, intestinal dysbiosis was suspected based on abnormal fecal bacterial culture results. A recent study has demonstrated that fecal bacterial culture, although still commonly used, is not useful to assess the intestinal microbiome as most bacteria are strict anaerobes that cannot be cultured using standard laboratory procedures.²² A molecular-based test for assessing intestinal dysbiosis, the fecal Dysbiosis Index (bit.ly/3Ug3ygz), was not available at that time, and consequently, it remains unknown whether Anton had an altered microbiome.²² While major changes in the intestinal microbiota are often secondary to antibiotic administration²³ and changes in the mucosal structure in CEs,²⁴ it is important to note that inadequate dietary substrate, in this case low-digestible protein, can also induce gastrointestinal signs, even if there are no or only minor shifts in the microbiome.¹⁹ Therefore, dietary trials with diets with improved digestibility should be considered even in animals with suspected or confirmed dysbiosis, as dietary modulation alone has shown partial recovery of the microbiome over time.^25,26

There are several possibilities if fecal consistency is more normal in the morning and becomes progressively worse during the day. The stool overnight has spent the longest period of time within the colon, allowing the most water reabsorption. In addition, the pet is more active during the day, and with each meal or treat, peristalsis is triggered more frequently (gastrocolic reflex). Based on the experience of the authors, this can often suggest problems with digestibility. In such cases, the authors probe for details about the type of food—especially treats—and also the routine and timing of foods and treats. Nutritional management is often performed empirically as a first step in those animals with milder clinical activity scores (BOX 1) and no signs of systemic disease, even before extensive testing is performed to investigate for underlying intestinal disorders and/or microbiome dysbiosis. These can include, as in Anton’s case, simple elimination of low-digestible treats. Additional steps may include dietary management with highly digestible gastrointestinal diets, hydrolyzed protein diets, and/or the addition of fiber either as supplements (e.g., psyllium husk, cellulose) or fiber-enriched diets.^7,28,29

BOX 1 Scoring Index27

Different scoring systems have been developed to assess the severity of inflammatory bowel disease (IBD) in dogs. The most commonly used clinical scoring is the Canine IBD Activity Index, or CIBDAI. The CIBDAI score is the summation of 6 different clinical signs: attitude/activity, appetite, vomiting, stool consistency, stool frequency, and weight loss.27 This numeric index and scoring system can be used by the clinician to guide therapeutic strategies for canine patients with IBD.

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