DM (Dry Matter)
DM — Dry Matter — is the portion of any feed ingredient that remains after all moisture has been removed. It is the foundation for every meaningful nutrient comparison in cattle nutrition, because moisture varies enormously between ingredients (green fodder is 80% water; compound feed is 11% water) and would otherwise distort all comparisons.
How DM is measured
A weighed sample of feed is dried in an oven at 100–105°C until weight stops changing (typically 24 hours). The dried weight, divided by the original wet weight, gives the DM percentage.
DM % = (Dry weight / Fresh weight) × 100
Why DM matters
All nutrient comparisons — protein, fat, fibre, TDN, mineral content — are reported on a dry matter basis so that a wet ingredient can be compared fairly to a dry one.
Example: 25 kg of fresh green fodder (20% DM) and 5 kg of compound feed (89% DM) might seem like different sizes, but their dry matter contributions are:
- Green fodder: 25 × 0.20 = 5 kg DM
- Compound feed: 5 × 0.89 = 4.45 kg DM
Comparable amounts of nutrition.
Typical DM content of common feed ingredients
| Ingredient | Dry matter % |
|---|---|
| Soybean meal | 89–90% |
| Maize (grain) | 87–90% |
| Compound cattle feed | 89% (11% moisture max per BIS) |
| Dry fodder / straw | 88–92% |
| Maize silage | 30–40% |
| Green fodder (mature) | 22–30% |
| Green fodder (young) | 15–20% |
| Fresh berseem / lucerne | 14–18% |
| Sugarcane tops | 25–30% |
| Whole milk | 12–13% |
Dry matter intake (DMI)
The amount of dry matter an animal eats per day is called Dry Matter Intake or DMI. Targets:
| Animal class | DMI (% of body weight) |
|---|---|
| Lactating cow | 3.0–3.5% |
| Lactating buffalo | 2.5–3.0% |
| Heifer | 2.5–3.0% |
| Dry cow | 2.0–2.5% |
| Calf (4–6 months) | 3.0–3.5% |
For a 450 kg lactating cow, DMI target is approximately 13.5–15.8 kg per day.
How dry matter shifts during storage and across seasons
Dry matter is not static — it changes meaningfully under storage and weather conditions:
- Compound feed loses DM during monsoon — bags stored in 75%+ humidity warehouses pick up 1-3 percentage points of moisture, dropping effective DM and accelerating mould growth. This is why BIS specifies 11% moisture maximum for compound cattle feed
- Green fodder DM changes dramatically through the day — fodder cut at 6 AM (high dew, 18% DM) loses ~3 percentage points by 11 AM (sun-dried, 21% DM). For silage making, harvest timing matters because target DM is 30-40%
- Hay and straw lose DM during baling and stacking — open-air stacks gain moisture during monsoon and lose it during summer, with the surface 10 cm of a stack varying 10-15% in DM from the core
- Maize silage stabilises within weeks — fresh silage at sealing is 30-35% DM; well-fermented silage is the same DM 6 months later, as long as the seal holds. A leaking silo causes both moisture re-entry AND DM loss through aerobic spoilage
Why farmers should care about DM in practice
A farmer who feeds "5 kg of compound feed and 30 kg of green fodder" thinks they're feeding 35 kg. On a DM basis it's 5 × 0.89 + 30 × 0.20 = 10.45 kg DM — not enough for a high-yielding lactating cow that needs 13-15 kg DMI. The animal looks well-fed but is under-producing because the wet bulk masks an actual DM deficit.
The reverse problem also occurs: feeding too much DRY fodder (wheat bran, straw) over-fills the rumen on a DM basis but undersupplies protein and energy. DM accounting is the only way to spot these mismatches early.
Practical use
When formulating any ration, compute the DM contribution of each ingredient first, then sum them to get total DMI. The total ration's CP%, TDN%, fat%, and fibre% are calculated on the combined DM basis. This is how the DCP and TDN calculator and the ration cost calculator compute their numbers.