Determination of Acid Detergent Fiber (ADF) in Animal Feed Using FT900 Fiber Determination Apparatus_NEWS

Determination of Acid Detergent Fiber (ADF) in Animal Feed

Introduction

After removing fat, starch, protein, sugars, and other components from animal feed using an acidic detergent, the remaining insoluble substances are collectively referred to as acid detergent fiber (ADF). These include cellulose, lignin, and small amounts of silicates.

Principle

Plant-based feed is treated with an acidic detergent, then washed with water and acetone. The residue left after washing is the acid detergent fiber (ADF).

Instruments and Reagents
3.1 Instruments
3.2 Reagents

Acid Detergent Solution (2% CTAB solution): Dissolve 20g of CTAB in 1000 mL of 1.00 mol/L sulfuric acid (1/2 H₂SO₄) solution, stir to dissolve.

Filtration Aids: Diatomaceous earth (ash at 500°C for 1 hour, placed in crucible).

Water: Use GB/T6682—1992 grade 3 water
Analytical grade chemicals
Sulfuric acid (H₂SO₄)
Hexadecyltrimethylammonium bromide (C₁₉H₄₂NBr, CTAB)
Acetone (CH₃COCH₃)
Petroleum Ether (60–90°C)
Hydrochloric acid (HCl)
n-Octanol (C₈H₁₈O, anti-foaming agent)

FT900 Fiber Determination Apparatus
Cyclone Mill
Analytical Balance
Forced-Air Drying Oven
100 mL Graduated Cylinder
Desiccator
Sample Sieve (mesh size 0.45mm², 40 mesh)
Crucibles (mesh size 40µm–60µm, domestic G2 crucibles)

Procedure
4.1 Clean, dry, cool, and weigh the crucibles. Record the weight. Add 1g of diatomaceous earth to each crucible (the diatomaceous earth should be acid-treated).
4.2 Accurately weigh 0.5g–1g of the dry sample or the degreased sample, accurate to 0.0001g. The sample should pass through a 40-mesh sieve.
4.3 Connect the power and water supply, and turn on the main power switch (ensure the water supply is adequate for effective condensation).
4.4 Place the crucible with the sample into the instrument's heating chamber (ensure the correct placement: the crucible should be centered on the heating rack, and the top should align with the inner hole of the protection sleeve of the digestion tube). Press down the handle to lock the crucible in place, and then press down the heating element handle.
4.5 Close the valve, take a 100mL graduated cylinder, and add 100mL of the acid detergent solution. Open the instrument's lid and pour the solution through the top funnel of the condensation tube. Add a few drops of tetrahydronaphthalene (anti-foaming agent). If the sample sticks to the sides of the container, rinse it with no more than 5mL of the acid detergent solution.
4.6 Acid Detergent Digestion: After adding 100mL of acid detergent solution, heat the mixture to a gentle boil for 60 minutes. Then, filter and wash the residue several times until no bubbles are visible. After filtering out the washing liquid, if the crucible becomes blocked, use the air pump to backflush the filter and clear the blockage, then continue to filter out the solution. Afterward, add about 20mL of acetone and let it soak for 5 minutes, then filter again (repeat three times). After finishing, remove the crucible, allow the acetone to evaporate slightly, and transfer the crucible to a drying oven at 105°C for 4 hours. Then, transfer the crucible to a desiccator to cool for about 30 minutes before weighing it to a constant weight.
4.7 Calculation of Results:
ADF% = (M₁ - M₂) ÷ M × 100
Where:

M₁: Weight of the crucible with ADF (in grams)
M₂: Weight of the empty crucible (in grams)
M: Weight of the sample (in grams)

Repeatability
For each sample, measure two parallel samples and take the average as the final result. For ADF content ≤10%, the relative deviation should not exceed 5%; for ADF content >10%, the relative deviation should not exceed 3%.

Determination of Acid Detergent Fiber (ADF) in Animal Feed Using FT900 Fiber Determination Apparatus

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