Technical note: Effects of filter bags on neutral detergent fiber recovery and fiber digestion in vitro

摘要

Filter bags facilitate the measurement of amylasetreatedneutral detergent fiber (aNDF) and in vitro (IV)undigested aNDF (uNDF) by eliminating the transferof residues from beakers into filtration crucibles. Theobjectives of this study were to (1) determine effectsof filter bags on recovery of aNDF and (2) evaluate effectsof filter bags on IV uNDF. For study 1, 6 sampleseach of grass hay (GR), alfalfa (AL), and corn silage(CS) were selected. Large standard deviations (SD)of ash-free aNDF (aNDFom) for samples in each foragetype indicated compositional diversity (15.1, 7.45,and 12.9% of DM for GR, AL, and CS, respectively),and starch SD for CS was 16.4% of DM. Samples wereweighed into Berzelius beakers or filter bags [25-μmpores (F57) or 6-μm pores (F58); Ankom Technology,Macedon, NY] for measurement of aNDF and aNDFom.All samples were extracted with neutral detergent,thermostable α-amylase, and sodium sulfite, and thensoaked in boiling water and then acetone. Residuesfrom beakers were filtered through a sea sand–coveredGF/D filter (Whatman, Marlborough, MA) in Goochcrucibles (CR). Filter bags were extracted in a pressurizedchamber at 100°C. The aNDF values did not differbetween F57 and CR, but F58 was greater than CRfor CS and AL. For GR, F58 was greater than CR foraNDFom. For study 2, diverse samples with large SDof aNDFom (20.7, 7.45, and 12.9% of DM for GR, AL,and CS, respectively) were weighed as loose powder intomedium bottles (LS) or F57 bags, which were weightedto prevent floating. Blended ruminal fluid from 3 steersfed a 30% aNDFom diet was used as inoculum. Threesamples of 1 forage type were randomly assigned to 1of 6 IV runs using both treatments (LS and F57), and3 bottles of each sample–treatment combination wereremoved after 12 h and 2 were removed after 120 hto measure uNDF. For LS, residues were extracted asin study 1 for CR. For F57, bags were rinsed in coldwater and extracted as described in study 1. After 12h, uNDF of F57 was greater than LS in CS, AL, andoverall types. Ash-free uNDF (uNDFom) after 12 h ofF57 was greater than LS in CS and overall types. After120 h, F57 was greater than LS for uNDF of CS, butno differences were detected for uNDFom. The SD ofuNDFom, but not uNDF, was higher after 12 and 120h for F57 compared with LS. From 6 to 96 h, overallgas production of F57 was less than LS, and F57 wasless than LS for CS from 3 to 96 h. Overall, LS gavegreater maximum and faster rates of gas productionthan F57, as did AL and CS, but lag did not vary.Results indicate that filter bags affected aNDF andaNDFom measurement and inhibited fermentation forsome materials.