Maize Silage Feeding After Drought Condition

Maize Nutritional characteristics under drought situation

Under drought stressed conditions we observed:

  • Lower yields
  • DM content variation: In field and between fields and so in the silo
  • Energy content : Feed value is app. 80%, but varies between 70% and 100%
  • Low level of starch: even lower than 10% DM basis
  • High levels of sugar: Up to 20% DM basis; sugar is fermented rapidly in the rumen and the acidosis risk increases.
  • More ADF and NDF content: decrease in total forage digestibility, but NDF digestibility can be increased. Due to possible higher NDF digestibility the passage rate in the rumen can be more rapid.
  • Higher crude protein content (10%): but more NPN (Non protein nitrogen), ammonia affects liver negatively and increase milk urea.
  • High levels of Nitrates
Figure 1. Maize silage analysis (1,386 samples, 1º. Jul – 7 Aug, 2012 (Dairyland Labs)). The year 2012 was a drought year in the US.


 Solutions and recommendations

  • Adapt your diet to the changed maize silage characteristics and maybe ask specialized feed consultant. Adjust the energy balance as well as energy and nitrogen availability in the rumen. Fast energy needs also fast protein. Don’t feed additional NPN. Check rumen filling, feed intake and subclinical acidosis signs.
  • Analyze silage on a regular basis to adapt adequately your diet.
  • Take care with high DM variation (from 25% up to 45%).
  • Analyze the kernel processing of the silage to adapt the feeding strategy.

Nitrates content

  • When plant growth is retarded by adverse growing conditions or when excessive amounts of nitrogen are available in the soil, nitrates not converted to protein accumulate in the plant stems and leaves.
  • Nitrates are converted to Nitrites, which interfere with the hemoglobin of the blood, preventing the regular transport of oxygen by the blood.
  • Symptoms: low body temperature, reduced consumption, weakness / low muscle tremors.
  • Lower third of the stalk contain up to 80 times more nitrate than leaves.
  • High nitrates may increase buffer capacity in the silage and nitrate can support clostridia and enterobacteria growth in the very beginning of the ensiling. Higher acetic acid concentration and dry matter losses can be a result.
Figure 2. Cornell University (nitrates-N content in ppm)


Solutions and recommendations

  • Test silage for nitrates content before feeding.
  • Adapt cows to nitrate containing feeds step by step.
  • A good ensiling reduces nitrate 30 – 50%, a specific silage inoculant will help here.

Gas production

  • Silage fermentation may produce several kinds of gas, including carbon dioxide and nitric oxide. Although carbon dioxide is non-poisonous, it can cause suffocation.
  • Nitric oxide changes to nitrogen dioxide when it contacts oxygen in the air. Nitrogen dioxide (NO2) is poisonous and can injure and kill people as well as livestock.
  • NO2: heavy gas, orange in color, accumulating in lower parts of the bunker
  • Smells like some laundry bleaches
  • The greatest danger from nitrogen dioxide gas from silage is during the first 12 to 60 hours after filling.
Figure 3. Firefighters, Germany, 2018


Solutions and recommendations

  • Be careful to the bleach-like odors and/or yellowish-brown fumes in or near the silo. Be alert the gas don’t enter the barn and harm the animals and employees.
  • Stay away at least 10 days from the silo, better two to three weeks. If you have to go, never go alone and place warning signs and explain children to stay away.

Listen to our podcast on silage gas here.

Yeasts, molds and mycotoxins risks

  • Higher yeasts risk contamination under drought condition (for example for this trial in US: 28% of the 183 samples have a yeast count above 10 000 000 CFU/g)
  • Risk in decreasing the feed intake due to alcohol production, losses of DM and energy, nitrates content
  • Risk of aerobic instability and reheating with a high level of remaining sugar. A high sugar content is more susceptible to reheating then a high starch content.
  • Drought stressed plant are more vulnerable to mold contamination and higher mycotoxins risks.

Figure 4. Yeast contamination (n=183, Jul-Sept 2012, Dairyland Labs)

Solutions and recommendations

  • Silage feed out management:
    • Do not uncover more of the silo than will be fed daily
    • Remove sufficient silage to prevent silage heating > 20cm
    • Do not allow silage to sit in piles, as it may start to deteriorate
    • Remove silage from the silo immediately before feeding
    • Use an appropriate toxin binder to deal with potentially high mycotoxin levels
  • Use of an heterofermentative bacteria inoculant will help preventing yeasts, molds and mycotoxin development in the silage
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