Feeding a balanced total mixed ration (TMR) is one of the most reliable ways to support herd performance, but even a perfectly formulated ration can fall short if one small detail is overlooked — the feed’s dry matter. Fluctuations in forage moisture can quietly throw off nutrient delivery, reduce feed efficiency, and cause unpredictable changes in milk yield and components.
What dry matter means for your ration
Dry matter (DM) is the portion of feed that remains after moisture is removed. Nutritionists use it as the basis for ration formulation because cows need a consistent supply of nutrients — not water — in every bite.
If a ration is mixed “as fed” without accounting for current moisture levels, the balance between energy, protein, and fiber can shift. Wet silage may dilute nutrients, while drier feed can create excess energy or starch. Either way, the cow receives something different from what was intended on paper.
Penn State Extension notes that even small changes in feed moisture can “cause shifts in feed weight, resulting in an unbalanced diet if not adjusted” (Penn State Extension).
The impact of moisture variation
Research continues to highlight how feed moisture directly affects performance.
An Ohio State University study found that when forage dry matter dropped by roughly 10 percentage units, cows consumed more feed on an as-fed basis but produced milk with lower fat content. The study concluded that short-term fluctuations may not always require a full ration reformulation — provided the producer monitors and adjusts feeding amounts accordingly (MSU Extension).
Other research published in the Journal of Dairy Science reported that varying dietary dry matter concentration through added water influenced feed intake, digestibility, and rumen fermentation patterns. Stable dry matter supported more consistent microbial activity and milk solids (ScienceDirect).
The message is clear: maintaining steady DM across feed batches helps stabilize intake and supports predictable milk output.
Why it happens
Feed moisture is constantly changing. Rainfall, humidity, silo management, and the position of silage in the pile all influence dry matter. Forages near bunker edges or exposed to air tend to dry faster, while newly opened silos can have higher moisture.
When these shifts go unchecked, the ration a cow receives may differ significantly from the one balanced by the nutritionist. That mismatch can alter rumen fill, increase sorting, and reduce feed conversion efficiency. The rumen ecosystem thrives on consistency — and moisture changes disrupt that rhythm.
How to stay on target
Maintaining dry matter accuracy doesn’t require complex tools — just consistent habits.
1. Test frequently.
Check silage and wet feed dry matter at least weekly. Many producers use portable moisture testers or a simple microwave test to track changes.
2. Adjust the ration as needed.
When moisture increases, raise the as-fed inclusion rate; when feed dries out, lower it. Keep ingredient proportions the same.
3. Watch feed refusals.
If leftover feed looks drier, courser, or contains more long forage, it may signal a shift in moisture or sorting behavior.
4. Calibrate mixer scales.
Scales that drift out of calibration can amplify feeding errors. Check equipment quarterly, or whenever load weights seem inconsistent.
5. Work closely with your nutritionist.
Persistent moisture swings lasting more than a few days may require a ration re-balance. A proactive plan helps avoid production dips.
At the feed bunk
Consistency counts. Even small variations in dry matter can quietly change nutrient balance and affect performance. A few quick checks each week help ensure cows receive the ration that’s intended — not a diluted or concentrated version. The payoff is steadier production, fewer digestive issues, and better use of every kilogram of feed mixed.
