Comparison of Neutral Detergent Fiber Analysis Methods for Feed Ingredients, Diets, and Feces of Pigs.

Background: An accurate determination of fiber concentrations in feeds and feces is critical for the measurement of fiber digestibility in pigs. The method of AOAC INTERNATIONAL for determining amylase-treated neutral detergent fiber (aNDF; Method 2002.04) has been widely used for pig diets. To overcome the complexity of the AOAC procedure, the Ankom method is also available for determining aNDF. Although these two methods have been compared for ruminant diets and feces, a comparison of the methods for pig diets and feces has not been documented.

Objective: The objective was to compare aNDF values determined by the AOAC (aNDFAOAC) and the Ankom methods (aNDFAnkom) of ingredients, diets, and feces for pigs.

Methods: A total of 255 test samples, consisting of 26 feed ingredients, 39 diets, and 190 feces of pigs, were analyzed for aNDF. To compare the AOAC Method 2002.04 and Ankom methods for aNDF, regression analyses were performed with the aNDFAnkom minus the mean aNDFAnkom as an independent variable and the aNDFAOAC minus the aNDFAnkom as a dependent variable.

Results: The aNDFAnkom were greater than the aNDFAOAC by 2.90% (standard error = 0.63; P < 0.001) on average for ingredients and by 2.56% (standard error = 0.34; P < 0.001) on average for diets. For feces, the aNDFAnkom were greater than the aNDFAOAC by 1.30% (standard error = 0.32; P < 0.001) on average. The differences between the aNDFAnkom and aNDFAOAC were not consistent across the data ranges represented by a linear bias (slope = -0.16; standard error = 0.04; P < 0.001) in feces.

Conclusion: ANDF concentrations determined by the Ankom method were greater than from the AOAC method in pig feeds and feces.

Highlights: Despite convenience, the Ankom method yields greater aNDF values compared with the AOAC method.