Comparison of using a reflux apparatus or ANKOM Fiber Analyzer with sequential or direct analysis to evaluate the fiber content in various feeds.

Two types of apparatuses, a reflux apparatus (RA) and the ANKOM Fiber Analyzer (AFA), are currently being used for the fiber analyses of feeds. In addition, the measurement of the ADF concentration in feeds may be conducted by sequential analysis (S) following an NDF extraction or directly (D) with the original feed. The objectives of this study were to evaluate NDF content of various feeds using RA or AFA and ADF content using RA or AFA with D or S (RAD, AFAD, RAS, and AFAS). PROC Mixed was performed on each feed, with models: NDF = apparatus + residual, or ADF = apparatus + method + apparatus x method + residual. The samples used were two sources of alfalfa hay (1 and 2), com silage (1 and 2), dried distillers grains plus solubles (1 and 2), grain mixes (1 and 2), and TMR (1 and 2), and one source of soybean meal, soybean hulls, whole cottonseed, sunflower seeds, and feces. Six replicates were used for each analysis. With the exception of soybean meal and sunflowers, the NDF content was determined to be greater (P < 0.05) in samples analyzed with RA compared to AFA. Acid detergent fiber for alfalfa-1 (30.9 vs. 29.5%), feces (33.2 vs. 31.1%), soybean meal (8.7 vs. 5.9%), soybean hulls (47.0 vs. 45.7%), and TMR-1 (22.3 vs. 20.7%) was greater (P < 0.05) when measured with AFA versus RA. In addition, the ADF in alfalfa-1 (32.0 and 28.4%), com silage-1 (27.8 vs. 25.6%) and 2 (28.0 vs. 26.5%), feces (34.0 vs. 30.3%), grain mix-2 (8.2 vs. 5.4%) soybean meal (9.0 vs. 5.6%), soybean hulls (46.9 vs. 45.8%), and TMR-1 (21.6 vs. 19.8%) and 2 (23.8 vs. 19.2%) was greater (P < 0.02) with D versus S. An interaction (P < 0.05) between apparatus and method was observed in corn silage-2, soybean meal, and soybean hulls, such that the decrease in ADF from AFAD to AFAS in these samples was much greater compared to the decrease in ADF from RAD to RAS. In conclusion, analysis with RA vs. AFA yielded increased values for NDF in most of the samples analyzed and decreased ADF in some of the samples. Analyzing samples with S decreased ADF in most feeds compared to D. [ABSTRACT FROM AUTHOR]