ADF (Acid Detergent Fibre)
ADF — Acid Detergent Fibre — is the measure of the least digestible portion of plant cell walls in cattle feed: cellulose and lignin. ADF is determined by boiling a feed sample in an acid detergent solution that dissolves hemicellulose along with cell contents, leaving cellulose and lignin (plus some minerals).
ADF is a strong predictor of feed digestibility and energy density. As ADF rises, digestibility falls. A high-ADF feed has more indigestible material the animal must move through its gut without extracting nutrition.
ADF vs NDF
NDF measures total cell wall (hemicellulose + cellulose + lignin). ADF measures only the harder-to-digest part (cellulose + lignin).
Hemicellulose (digestible fibre) = NDF − ADF
The hemicellulose fraction, NDF minus ADF, is the fibre portion that rumen microbes can ferment into useful energy. ADF itself is largely indigestible — particularly the lignin portion, which essentially passes through the animal unchanged.
Typical ADF values
| Ingredient | ADF (DM basis) |
|---|---|
| Maize | 3–5% |
| Soybean meal | 6–8% |
| Bypass protein (premium) | 10–12% |
| Cotton seed cake | 18–25% |
| Wheat bran | 10–14% |
| DORB | 12–16% |
| Maize silage | 22–28% |
| Green fodder (young) | 25–30% |
| Green fodder (mature) | 35–45% |
| Wheat / paddy straw | 50–60% |
Why ADF matters for ration formulation
ADF correlates inversely with energy density. A practical relationship:
Higher ADF → Lower TDN → Less energy per kg of feed
This is why lactating cows producing 15+ litres per day need low-ADF rations — their energy demand exceeds what a high-ADF (mature forage, lots of straw) ration can deliver per kilogram of intake.
Target ADF for a high-yielding lactating cow: 18–22% of total ration DM. For a maintenance ration, ADF can go higher (25–30%) because the energy demand is lower.
ADF in lab analysis
ADF is measured by sequential acid-detergent extraction in a standard lab (typically the Van Soest procedure). Cost is moderate (₹300–500 per sample at a certified Indian feed analysis lab). For commercial dairies, periodic ADF testing of green fodder and silage is standard practice.
Practical use
NDF and ADF together give a complete fibre profile:
- High NDF + High ADF → Low digestibility, low energy (mature straw)
- High NDF + Low ADF → More digestible fibre, moderate energy (silage, young green fodder)
- Low NDF + Low ADF → High concentrate, high energy (compound feed)
The right ration balance depends on the animal — high-yielders need low ADF, dry cows tolerate higher.