Silage is often considered the foundation of a profitable dairy ration. This is because even small losses in quality can reduce milk production, increase feed costs, and affect herd health.
Fortunately, assessing silage quality does not require sophisticated equipment. Farmers can identify many defects simply by looking, smelling, and feeling the silage before sending samples for laboratory analysis.
Start with your senses
Good-quality silage should have a light green to olive-green colour. While slight browning can occur naturally, dark brown or black silage usually indicates excessive heating during storage, which reduces its nutritional value.
The smell is equally important. Well-fermented silage should have a pleasant, fruity, slightly acidic aroma. Silage that smells rotten, rancid, mouldy or strongly of ammonia has undergone poor fermentation and should be investigated before being fed.
Texture also provides valuable clues. Good silage should feel soft and fibrous without being slimy or excessively dry.
Look out for mould
Visible mould is never a good sign. White, blue, green, or black mould indicates that oxygen has entered the silage, allowing spoilage organisms to grow. Surface mould can sometimes be removed safely, but extensive mould growth usually points to poor sealing or inadequate compaction.
The presence of soil, manure, stones, or plastic contamination should also raise concern, as these reduce feed quality and can introduce harmful bacteria.
Watch for heating
Freshly exposed silage should remain cool. If the silage becomes warm or hot after the bunker has been opened, yeasts and moulds are likely becoming active. Heating reduces feed quality and often causes cows to refuse to consume the ration.
During warm weather, farmers should remove sufficient silage from the bunker face each day to prevent heating and maintain a smooth and vertical feed face.
The right moisture makes all the difference
One of the biggest determinants of silage quality is harvesting at the correct dry matter content.
Silage that is harvested when it’s too wet often ferments poorly, producing undesirable acids that reduce palatability.
Silage that is too dry becomes difficult to compact, allowing oxygen to remain trapped inside the bunker and increasing spoilage losses.
For maize silage, the ideal dry matter content is generally between 32% and 38%, which usually corresponds to the milk line being halfway to two-thirds down the kernel.
Laboratory analysis still matters
While visual assessment is useful, laboratory analysis remains the best way to determine nutritional quality.
Farmers should have representative samples analysed at least once every season for:
- Dry matter;
- Crude protein;
- Starch;
- Neutral detergent fibre and acid detergent fibre;
- Energy value;
- Potential of hydrogen; and
- Fermentation acids.
These results enable nutritionists to balance rations accurately and identify potential fermentation problems before they affect milk production.
Good silage starts at harvest
Many silage problems begin long before the bunker is sealed.
Good management includes:
- harvesting at the correct maturity;
- using sharp knives and correctly adjusted kernel processors;
- filling the bunker as quickly as possible;
- spreading forage in thin layers;
- compacting continuously to exclude oxygen; and
- sealing the bunker immediately after filling.
Proper sealing with high-quality plastic and adequate weighting remains one of the cheapest ways to reduce spoilage losses.
A daily feed-out routine pays dividends
Silage management does not end once fermentation is complete.
Every day, farmers should check that:
- the feed face remains cool;
- no mould is developing;
- spoiled silage is removed;
- cows consume the silage readily; and
- feed refusals do not increase.
Any sudden drop in intake may indicate declining silage quality before laboratory results reveal a problem.
A simple traffic-light guide
🟢 Good-quality silage
- Olive-green colour;
- Pleasant fruity smell;
- Cool at feed-out;
- No mould;
- Cows clean up the ration.
🟡 Warning signs
- Slight browning;
- Mild heating;
- Small patches of surface mould;
- Increasing feed refusals.
🔴 Investigate immediately
- Black or very dark silage;
- Rotten, rancid, or ammonia smell;
- Extensive mould growth;
- Hot silage;
- Slimy texture;
- Soil contamination;
- Cows refusing to eat.
Good silage is not only about producing enough forage, but also about preserving as much of the crop’s nutritional value as possible. Careful harvesting, effective compaction, airtight sealing, and disciplined feed-out management all contribute to higher milk production, healthier cows, and improved profitability. A few minutes spent checking silage every day can prevent costly losses later in the season.
