NDF (Neutral Detergent Fibre)
NDF — Neutral Detergent Fibre — is the modern, more accurate measure of fibre content in cattle feed. It represents the total cell wall content of plant material: hemicellulose, cellulose, and lignin combined.
NDF is determined by boiling a feed sample in a neutral detergent solution that dissolves the cell contents (proteins, sugars, fats, starches) but leaves the cell walls behind. The residue, expressed as a percentage of dry matter, is the NDF.
Why NDF matters
NDF is the single best predictor of dry matter intake in dairy cattle. As NDF rises, an animal cannot eat as much because the rumen fills up faster. Conversely, very low NDF feeds risk acidosis and reduced rumination.
| Ration NDF target | Typical use |
|---|---|
| Below 28% (DM basis) | Risk of acidosis; insufficient rumen scratch |
| 28–34% | High-production target for early lactation |
| 35–40% | Standard lactation ration |
| 40–50% | Late lactation, dry cows, heifers |
| Above 50% | Maintenance only; intake will be limited |
NDF vs Crude Fibre
The older "Crude Fibre" measure (still required on BIS labels) is calculated by acid-and-alkali digestion and captures only part of the cell wall. NDF captures more — hemicellulose is included in NDF but not in Crude Fibre.
Roughly: NDF ≈ 2–3 × Crude Fibre for typical Indian feed ingredients. Modern dairy nutrition uses NDF for ration formulation; BIS labels still report Crude Fibre for regulatory purposes.
Effective NDF (eNDF) — the "scratch factor"
Not all NDF is equal. Physically effective NDF (peNDF) is the fraction of NDF that is in long enough particles (typically over 1.18 mm) to stimulate rumen contraction, cudding, and saliva production. A ration high in total NDF but low in peNDF (e.g., finely ground hay-based ration) can still cause acidosis.
This is why TMR target a forage chop length of 1–4 cm with about 5–15% of particles above 4 cm — to deliver enough peNDF for healthy rumen function.
Typical NDF values of common Indian feed ingredients
| Ingredient | NDF (DM basis) |
|---|---|
| Maize | 8–12% |
| Soybean meal | 12–15% |
| Cotton seed cake | 25–40% (undecorticated higher) |
| Wheat bran | 35–45% |
| DORB | 30–40% |
| Maize silage | 40–50% |
| Green fodder (young) | 35–45% |
| Green fodder (mature) | 50–60% |
| Wheat / paddy straw | 65–80% |
| Legume hay (berseem) | 35–45% |
Practical use
When formulating a lactating cow ration, target total ration NDF on a DM basis at 35–40% for moderate-yield, 30–35% for high-yield. Below 28% is acidosis territory; above 45% intake will drop. Ensure at least 19–22% of NDF is from physically effective sources (long-stem forage).
NDF and its companion measure ADF together give a complete picture of fibre quality.