Evaluating accuracy of neutral detergent fiber methodology on effluent samples from dual-flow continuous culture fermenters

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Ruminant animals such as cattle can utilize fiber as an energy source. Fiber is the carbohydrate portion of feed that can only be digested by gastrointestinal microbes. The neutral detergent fiber (NDF) system is used to calculate three fiber components of a sample: lignin, cellulose, and hemicellulose. Accurate NDF measurements are beneficial when calculating nutritional value and digestibility of feeds. Dual-flow continuous culture fermenters (DFCC) are used to mimic rumen function and examine feedstuff digestibility in the ruminant system without the cost of an animal trial. Effluent samples from fermenters are finely ground, which makes it more challenging to filter the sample during the NDF procedure. My objectives were to compare filter types (paper vs. microfiber) and determine which was more accurate compared to a commercial laboratory standard. My secondary objective was to evaluate the effect of ash contamination on NDF results. My hypothesis was that the 934-Ah microfiber filters (AhMF) would be more accurate for determining NDF content of fermenter samples. My other hypothesis was that ash percentage in feed samples would have a direct effect on both filtering time and NDF accuracy. To make this comparison, dried effluent samples (n=24) from 3 previously published DFCC trials were assayed for NDF in triplicate and filtered by 541 paper filters (PF) or AhMF. In a second experiment, 3 feed samples (alfalfa hay, brewer's grains, and corn silage) were dried (55C), ground (2mm) and assayed for NDF using the PF. Ash was obtained by burning biochar at 550C. Each feed sample was contaminated with a differing level of ash (0%, 20%, 30%, 40%, and 50%) and run in triplicate. The AhMF and PF had a mean difference from the commercial laboratory standard of -2.86 and -2.50 respectively (P<0.0001). In experiment 2, ash contamination had a direct effect on increasing the amount of NDF retained on the filter (P<0.0001). These data indicate that ash contamination has a significant effect on the recovery of NDF values using the reflux method. Since DFCC effluent samples are around 50% ash, more work is needed to determine the best method to obtain accurate NDF values.


Animal and Insect Sciences (The Ohio State University Denman Undergraduate Research Forum)


animal nutrition, feed analysis, fiber digestibility, ash contamination