Determination of Neutral Detergent Fiber (NDF)

Principle

Insoluble fiber in feed is determined as neutral detergent fiber (NDF). Neutral detergent solution recovers its main components cellulose, hemicelluloses and lignin.

Procedure

• Weigh oven-dry glass crucible (Wt)

• Add 0.5–1 g sample (Ws) in 600 ml Berzelius beaker

• Add 100 ml of neutral detergent solution and 0.5 g sodium sulfite

(Na2SO3)

• Boil for one hour in refluxing apparatus (Fig. 15)

• Pour through glass crucibles (Fig. 17)

• Admit vacuum (Fig. 16)

• Rinse crucibles with approximately 50 ml hot water four times until

all traces are removed

• Rinse with acetone repeatedly until drained liquid is cleared.

• Dry at 105 °C overnight

• Cool to room temperature in desiccator

• Weigh sample and crucible (W0)

• Ash residues for three hours at 550 °C

• Cool to room temperature in desiccators

• Weight crucibles and residues (Wa).

Calculations

%NDF = [(W0–Wt)/Ws]×100

Cell soluble material = 100 – %NDF

NDF expressed as organic matter:

Ash insoluble in neutral detergent

%NDFash = [(Ws–Wt )/(W0–Wt)]×100

Neutral detergent solution

• 2 l distilled water.

• 60 g sodium lauryl sulfate (C12H25O4S)

• 37.22 g disodium dihydrogen EDTA (C10H14N2Na2O8)

• 13.62 g sodium borate (decahydrate) (Na2B4O7.10H2O)

Figure 15. Refluxing apparatus 13

• 9.12 g disodium hydrogen phosphate (Na2HPO4)

• 20 ml 2–ethoxy–ethanol (C4H10O2)

• Adjust pH 6.9–7.1.

Equipment

• Precision balance (Fig. 5)

• Refluxing apparatus (Fig. 15)

• Vacuum filtering system with

trap in line (Fig. 16)

• Desiccator (Fig. 7)

• Berzelius beakers (600 ml)

• Sintered glass crucibles

(coarse porosity 1) (Fig. 17).

References

• Goering HK and VanSoest PJ. 1970.

• Van Soest PJ, Robertson JB and Lewis BA.1991.