Crude Fiber and Total Dietary Fiber Concentrations of Popular, Premium, and Clinical Canine Diets Fed to Client-Owned Osteoarthritic Dogs

Dietary fiber has been used as a nutritional strategy in the management of osteoarthritis (OA) in companion animals. The non-enzymatically digestible quality of dietary fiber has been shown to aid in weight loss through lowering caloric density of pet foods. Crude Fiber (CF) is the officially required fiber method in the pet food industry. However, it only measures portions of insoluble fractions of the total dietary fiber (TDF) content. With clinical cases in which weight management is an important outcome, accurate determination of the dietary fiber content is crucial, and the correlation between CF and TDF measurements must be questioned. The objective of this study was to compare the analyzed concentrations of CF and TDF of commercial diets fed to a cohort of client-owned osteoarthritic dogs. These data were derived from a larger study evaluating multiple parameters of the lifestyle, medical, and dietary history of dogs with osteoarthritis. As part of this study, samples of food from client-owned dogs were evaluated for macronutrient composition, and labels of the diets were provided by the dog-owners. A total of 51 different diets were collected and subsequently characterized into three main categories: Popular (n=11), Premium (n=32), and Clinical (n=8). Our hypothesis was that the correlation between the analyzed concentrations of CF and TDF would be low due to the extreme variability and the inaccuracy of the CF assay. All diets were analyzed for dry matter and ash (AOAC, 2006), CF (AOAC, 2006), and TDF (Prosky et al., 1988). A linear regression was performed to analyze the correlation between CF and TDF measurements. The correlation between CF and TDF measurements was statistically significant (p < 0.001; r=0.7086). With the exception of one sample, TDF values were greater than CF values. On average (mean ± SD), TDF values were 5.24 ± 2.53 percentage units greater than CF values, with a range of 65% to 332% of the analyzed CF content. These results suggest that CF analysis leads to an incomplete and inaccurate measurement of dietary fiber content and for this reason should not be utilized as a predictor of dietary fiber content.