Comparison of neutral detergent fiber methods

Authors: Hall, Mary Beth; MERTENS, DAVID - Mertens Innovation & Research, Llc

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/8/2023
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Neutral detergent fiber (aNDF) is the most commonly reported fiber metric in dairy cattle nutrition. An empirical analyte, the method (M) used defines aNDF. The definitive method is AOAC Official Method 2002.04, performed on samples ground to pass the 1-mm screen of a cutting mill (1CM) with refluxing and then filtration through Gooch crucibles without (AOAC-; definitive M) or with (AOAC+) a glass fiber filter. Other M in use include grinding materials through the 1-mm screen of an abrasion mill (1AM), filtration through a Buchner funnel with a glass fiber filter (Buch), and the ANKOM filter bag system (ANKOM Technology, Macedon, NY) using filter bags with 25 micron (F57) or 6-9 micron (F58) particle size retentions. Our objective was to compare AOAC and alternative M using feeds processed with 1CM and 1AM. Two alfalfa silages, two corn silages, dry ground and high moisture corn grains, grass hay, ryegrass silage, soybean hulls, calf starter, and sugar beet pulp were analyzed in duplicate in replicate analytical runs performed on different days. Data were analyzed as a completely randomized design with a 2 x 3 factorial arrangement of treatments. Significance declared at P < 0.05, and tendency at 0.05 < P < or = 0.10. The aNDF% of dry matter (aNDF%) from 1AM as compared to 1CM ground feeds were or tended to be lower for 8 of 11 feeds. Method affected aNDF% results for all feeds, with M x grind interactions for 6 of 11 feeds. For ash-free aNDF% of 1CM ground feeds, a priori selected contrasts showed that the number of feeds for which M differed or tended to differ from AOAC M were Buch: 4, F57: 8, and F58: 3; and 3 for AOAC- versus AOAC+. Evaluation of how many mean feed aNDF% values fell outside of the 2 standard deviation range from AOAC- means for 1CM and 1AM ground feeds, respectively, were AOAC-: 0, 4; AOAC+: 0, 2; Buch: 2, 2; F57: 8, 10; and F58: 4, 7. We conclude: 1) 1CM grinds or equivalent are necessary for the NDF M tested to agree with the AOAC reference M; 2) with 1CM grinds, M in order of agreement with AOAC are Buch, F58, and last, F57 which often produced lower values; 3) as an allowed modification of AOAC-, AOAC+ is worthy of consideration for general use. Further evaluation with an expanded sample set is needed.