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.
How ADF changes with crop maturity
The single biggest driver of ADF in any forage is the stage at harvest. As a plant matures, the cell walls thicken with cellulose and lignify — ADF rises steeply through the growing season:
| Plant stage | Typical ADF | Energy effect |
|---|---|---|
| Boot / pre-bloom | 22-28% | Highest energy, lowest ADF |
| Early bloom | 28-34% | Still good — typical silage harvest window |
| Mid bloom | 34-40% | ADF rising fast; energy density dropping |
| Late bloom / seed set | 40-50% | Energy too low for high-yielders |
| Mature / dried on stem | 50-60% | Maintenance only |
This is why maize cut at the dough stage delivers much better ration energy than maize left in the field until grain hardens. The same physical mass of forage delivers 20-30% more usable energy when harvested at the right stage.
For hydroponic green fodder, ADF stays low (12-15%) because the sprouts are harvested at just 7-9 days, well before lignification begins. This is a key reason hydroponic fodder is so digestible per kg of DM.
Seasonal ADF patterns for Indian dairy
Indian forage ADF follows predictable monsoon-driven cycles:
- Post-monsoon (Sept-Nov) — best window for low-ADF silage harvest; cool, moist conditions favour leafy growth
- Winter (Dec-Feb) — irrigated fodder stays low-ADF; rain-fed crops harden and ADF rises
- Pre-summer (Mar-Apr) — ADF rises sharply as plants mature under heat stress
- Peak summer (May-Jun) — fresh green fodder scarce; what's available is high-ADF mature material. This is why silage made in Sept-Nov is so valuable in May-Jun
- Monsoon (Jul-Aug) — fresh growth restarts at low ADF, but waterlogged fields delay harvest
A dairy buying purchased green fodder in May-June often pays premium price for high-ADF material — energy density per rupee is poor. This is the strongest seasonal argument for on-farm silage production.
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.