Estimating energy contributed by fiber using a general factor of 2 vs 4 kcal/g

Effect of crude fiber and total dietary fiber on the calculated nitrogen-free extract and metabolizable energy content of various dog foods fed to client-owned dogs with osteoarthritis

OBJECTIVE

To compare measurements of crude fiber (CF) and total dietary fiber (TDF) for various dog foods and their effect on the calculated nitrogen-free extract and metabolizable energy (ME) content, and to compare label-guaranteed and laboratory-analyzed macronutrient values.

SAMPLES

51 dog foods fed to client-owned dogs with osteoarthritis.

PROCEDURES

Foods were analyzed for dry matter, ash, crude protein, acid-hydrolyzed fat, CF, and TDF. Metabolizable energy was calculated by use of a formula with modified Atwater factors and formulas recommended by the National Research Council that included both CF and TDF values. Linear regression analysis was performed to determine the correlation between CF and TDF values.

RESULTS

Only a few foods failed to conform to the guaranteed analysis for all macronutrients except for CF, in which approximately 40% of the foods exceeded the guaranteed maximum values. The CF and TDF values were moderately correlated (r = 0.843). Correlations among CF- and TDF-based ME estimations were moderate with use of the modified Atwater formula and strong with use of the National Research Council formulas (r = 0.86 and r = 0.91, respectively).

CONCLUSIONS AND CLINICAL RELEVANCE

Values for CF were the most variable of the macronutrients of the evaluated dog foods and results suggested that CF is an incomplete and inaccurate measurement of dietary fiber content and, thus, its inaccuracy may lead to inaccurate and variable ME values.