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

An accurate determination of fiber concentrations in feeds and feces is critical for the measurement of fiber digestibility in pigs. The method of AOAC for determining amylase-treated neutral detergent fiber (aNDF; method 2002.04) has been widely used for pig diets. To overcome the complexity of AOAC procedure, the Ankom method is also available for determining aNDF. Although these 2 methods have been compared for ruminant diets and feces, the comparison of the methods for pig diets and feces has not been documented. The objective was to compare aNDF values determined by the AOAC (aNDFAOAC) and the Ankom methods (aNDFAnkom) of ingredients, diets, and feces for pigs. A total of 255 test samples consisted of 26 feed ingredients, 39 diets, and 190 feces of pigs were analyzed for aNDF. To compare aNDFAOAC and aNDFAnkom, 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. The aNDFAnkom were greater than the aNDFAOAC by 2.90 percentage unit (standard error = 0.63; P < 0.001) on average for ingredients and by 2.56 percentage unit (standard error = 0.34; P < 0.001) on average for diets. For feces, the aNDFAnkom were greater than the aNDFAOAC by 1.30 percentage unit (standard error = 0.32; P < 0.001) on average. The differences between the aNDFAnkom and the 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. Amylase-treated neutral detergent fiber concentrations determined by the Ankom method were greater than the AOAC method in pig feeds and feces. Despite convenience, the Ankom method yields greater aNDF values compared with the AOAC method.