Six dry dog foods and six dry cat foods with different carbohydrate sources were investigated in digestion trials. Food and fecal samples were analyzed for crude fiber (CF), total dietary fiber (TDF) and starch. In dogs, neutral detergent fiber (aNDFom) and acid detergent fiber (ADFom) were also analyzed. N-free extract (NfE) was calculated for CF and all other fiber analyses.

Crude fiber analyses gave the lowest values and TDF the highest, while ADFom and aNDFom were in between. Variation between diets was lowest in CF and highest in TDF. Total dietary fiber, aNDFom and ADFom in food were positively correlated. CF did not correlate with any other method. The NfE analogue for TDF was closest to the starch content. Methods of fiber analyses in feces did not agree well with each other. CF had the lowest apparent digestibility, followed by ADFom, TDF and aNDFom.

For all analyses, there was a significant correlation between fiber intake and fecal fiber excretion. True digestibility was close to zero for CF, with a high uniformity in both species. In dogs, true digestibility of aNDFom was 53%, ADFom, 26% and TDF, 37%. In cats, true digestibility of TDF was 31%.

Except for CF, the intercept of regression equations suggests fecal excretion of some material of non-food origin is analyzed as fiber. A combination of TDF and CF analyses might give good information on the content of total (TDF), unfermentable (CF) and partially fermentable fiber (TDF-CF) in petfoods.

Source : L.D. de-Oliveira et al., 2011. Fibre analysis and fibre digestibility in pet foods – a comparison of total dietary fibre, neutral and acid detergent fibre and crude fibre. JAPAN online August 2011. doi: 10.1111/j.1439-0396.2011.01203.x