Discussion
While therapeutic veterinary gastrointestinal diets are commonly utilized in veterinary practice for the management of gastroenteritis, this was the first study to evaluate the efficacy of these diets in vomiting cats with chronic gastroenteropathy. The majority of cats in this study presented with chronic vomiting represented in 25 of the 28 cats (89%). There were no statistical differences between dietary treatments in the weekly mean vomiting frequency or change in weekly vomiting frequency over time. However, looking within dietary groups, cats fed Diet A showed a significant reduction in vomiting occurrences in weeks 2–4 compared to baseline, with a 63% reduction in the final week compared to baseline. Cats fed Diet B, while not reaching statistical significance, also showed a numerical reduction from baseline over the study period. Follow-up studies with additional cats are needed to better define the efficacy of Diet B and any potential differences between dietary treatments.
In addition to the change of mean weekly vomiting episodes within treatment groups, it was also of interest to consider the number of cats that reached resolution, or no vomiting episodes, over the weekly period. The probability of vomiting declined during the course of the study, with a significant decline in cats fed Diet A in weeks 2–4, with a 0.2 probability in the final week. Sixty seven percent (n = 8) of the cats fed Diet A and 47% (n = 7) of the cats fed Diet B had no vomiting episodes at the final week of the study. Of these 15 cats, 3 showed an episodic pattern over the 4-week period, with 1 or more weeks without vomiting followed by a later week with vomiting.
Chronic diarrhea was less common in this study population, with only two cats having concurrent vomiting and diarrhea and three cats with diarrhea alone. It was considered that there may have been a lack of awareness or appreciation of diarrhea in the cats given the absorptive nature of litter that could have made diarrhea less recognizable to owner. The FCS chart included images of stool within litter to help educate and increase awareness of the owners participating in this study; however, overall frequency of diarrhea remained low and did not significantly change over the 4-week period.
Data from Banfield Pet Hospital® visits between 2008 and 2012 showed that older cats are more highly represented among cases of chronic gastrointestinal disease (8). Because of this, it was considered that age may have been associated with more severe clinical disease; however, no significant correlation was observed between age and vomiting occurrence within this study population. Previous studies evaluating diagnostic outcomes of cats with chronic gastroenteropathy have shown that older cats (mean ages ranging from 9.3 to 12.6 years) were more likely to have an underlying neoplastic etiology compared to younger populations (mean age 7.7–8.9 years) (13, 14). The population in this present study was relatively younger (mean age of 7.2 years) and likely had less severe disease than those evaluated in previous studies at tertiary referral practices. Given the risk of underlying neoplastic disease in cats with chronic gastroenteropathy, dietary intervention in conjunction with additional diagnostics is warranted in older patients.
Similar to previous reports, we found a relatively high prevalence of cats that were positive for FCoV antibody and C. perfringens enterotoxin gene (15). Cats with a positive status were included within this study population, receiving dietary intervention alone. Similar to a previous report (15), a positive status did not correlate with the occurrence of vomiting or diarrhea over the study period. It should be emphasized that the presence of FCoV antibody and C. perfringens toxin gene does not necessarily denote infection nor does it indicate the need to initiate medical therapy. Similarly, antimicrobial therapy for Campylobacter spp. is not recommended in animals that are not immunocompromised or showing systemic signs of illness (fever, hemorrhagic diarrhea, abnormal leukogram findings) as it can prolong the carrier state and the diarrhea typically self-resolves with supportive care alone (16).
Both Diet A and Diet B are categorized as therapeutic gastrointestinal diets designed to manage non-specific acute and chronic gastrointestinal disorders. Although both diets share similar indications, there are nutritional differences between the two diets that are worth considering. The macronutrient distribution of protein, fat, and carbohydrate differed between the two formulas. The percent of calories from protein, fat, and carbohydrate were 31, 31, and 38% in Diet A and 35, 40, and 25% in Diet B, respectively (Table 1). While protein level was similar between the two formulas, the fat and carbohydrate contents varied more widely. Reduced dietary fat has been recommended in patients with gastroenteropathy due to potentially impaired fat absorption (7, 8); however, dietary fat was shown to have no difference in clinical response in cats with chronic diarrhea (6). The presence of concurrent chronic pancreatitis has also been an indication for feeding reduced or moderate fat diets in cats with gastroenteropathies (17); however, cats with increased fPL levels were excluded from this study. Carbohydrate malabsorption was previously reported in cats with IBD, but dietary carbohydrates were not shown to negatively impact clinical signs (18). The higher dietary carbohydrate content of Diet A, relative to Diet B, did not appear to negatively impact diet performance and was well tolerated.
In addition to total dietary fat, the fatty acid composition should also be considered. Based on the guaranteed analysis for total omega-3 fatty acids and inclusion of fish oil (Table 1), Diet A was expected to provide greater concentrations of long-chain omega-3 fatty acid. Dietary long-chain omega-3 fatty acids have been shown to modulate inflammation within the body, providing benefit to a variety of inflammatory medical conditions (19). The underlying etiology was not defined in this study; however, IBD is commonly reported in feline gastroenteropathy, and the use of omega-3 fatty acids may have a beneficial effect in modulating the inflammatory response (19). While the duration of this study was relatively short, fatty acid incorporation into intestinal tissues can occur fairly rapidly, with one study showing significantly higher concentrations of eicosapentaenoic acid and docosahexaenoic acid in human colonic tissue following 7 days of supplementation compared to controls (20). Additional studies evaluating diets with titrated levels of long-chain omega-3 fatty acids are required to better understand potential benefits in cats with chronic gastroenteropathy.
Finally, differences in dietary fiber and prebiotic ingredients may have influenced response. Crude fiber analysis was 2.22% in Diet A and 3.16% in Diet B. Total dietary fiber and the soluble and insoluble fractions were not analyzed in this study. These data would have helped to better characterize the dietary fiber composition of the diets; however, ingredient composition provides some insight as to how these two diets differ. Diet A utilized dried beet pulp, fructooligosaccharides, and mannanoligosaccharides, while Diet B utilized powdered cellulose followed by dried beet pulp. Based on the ingredient composition, Diet A would be expected to provide more fermentable fibers and prebiotics that may have promoted an increased production of total intraluminal short-chain fatty acids and positively influenced microbial populations (21–30). While dietary fiber and prebiotics are generally considered to provide benefits primarily within the large intestine and aid in the management of diarrhea, recent studies have demonstrated immune modulating benefits that could have broader benefits, particularly in conditions with an inflammatory nature (31, 32). The time required to see potential clinical benefits is unclear, and clinical improvement related to immunomodulation may require more than 1–2 weeks of dietary intervention. Additional studies are needed to better understand the role of the microbiota in inflammatory gastrointestinal disease and the potential benefits of dietary fibers and prebiotics in animals with chronic gastroenteropathies.
There were several limitations to this study, including the relatively small study population that was below the initial target of 25 cats per treatment group. Additional numbers may have been required to demonstrate a significant difference in Diet B and between the two dietary interventions. This study also relied on a comparison to baseline versus a comparison to a non-therapeutic control formula. A non-therapeutic control would have been ideal for establishing effectiveness of the therapeutic diets; however, due to ethical considerations, all study participants were provided with a therapeutic dietary intervention. Additionally, this study relied on the owner’s recall to establish the baseline weekly vomiting frequency. A recorded baseline would have been preferred; however, it was decided that it was not in the cats’ best interest to delay dietary intervention. Finally, the lack of significance may have been influenced by the variability of clinical disease within individual cats. It was appreciated in this study that while most cats had a progressive decline of vomiting occurrences, some cats had episodic occurrences of vomiting that varied from week to week (Figure 1). The 4-week feeding period was chosen to approximate a reasonable duration for a dietary trial with a gastrointestinal therapeutic formula before additional diagnostic procedures and/or medical treatments would be employed to better characterize and manage the underlying disease. While this study did not follow the cats beyond the 4-week period, it would have been optimal to evaluate this cohort for 4–6 months to identify whether there were recrudescence of clinical signs and any differences between the two diet groups long term.