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Boost fermentation in haylage

When making haylage or baleage (above 50% moisture), farmers depend on two factors to preserve the forage: absence of oxygen (anaerobic conditions) and fermentation that produces organic acids (lactic and acetic acids).

I am often asked whether or not a bacterial inoculum should be added. The answer is “yes” for chopped haylage Molds need oxygen for growth, so creating anaerobic conditions stops mold growth. This is why packing to remove air in a tube or bunker, or making a dense bale and wrapping it with adequate thickness of plastic is so important. In both cases, minimizing the oxygen reduces heating and loss of crude protein and total digestible nutrients, as well as preserves the haylage or baleage.

Anaerobic conditions also are required for fermentation by Lactobacillus bacteria, which only grow in the absence of oxygen. They convert the starch and sugars of the forage into acids that enhance preservation. Acid production helps preserve the haylage in storage, and greater acid production also slows mold growth on feedout when the haylage is again exposed to the air.

Cheap insurance

While Lactobacillus are always present in the field, they’re often at lower levels when the crop grows under cool conditions (first or last cutting), and may be limited on midseason cuttings. Since the cost is about 50 cents per ton, and more than 50 cents per ton worth of nutrients can easily be lost from spoilage due to low acid levels, using a Lactobacillus inoculum is cheap insurance.

For the inoculum to work, it must thoroughly cover the forage since the bacteria do not move within forage. Thus, the recommendation for chopped forage is to apply liquid inoculum on the chopper as the forage is being blown into the wagon or truck to get good coverage of each chopped particle; applying the inoculum to the top of chopped forage going into the bag or to the top of a layer in the bunker results in poor coverage and little enhanced fermentation.

Similarly, spraying inoculum onto a windrow as the baleage is being made results in poor coverage. (Think of it as spraying paint on the windrow.) There is no movement of the Lactobacillus bacteria, so the small percentage of forage inoculated results in little enhanced fermentation. Thus, inoculation is not recommended for baleage since good coverage cannot be achieved. (Note that good fermentation can still occur in baleage if natural inoculation with Lactobacillus is high.)

Lactobacillus bacteria also need food (starch and sugar) to grow. Normally, early harvested forage for high quality has adequate starch and sugars for fermentation, while late-harvested forage (alfalfa at mid- to late flowering or grass that is headed) may not.

Also, cut forage respires (breaks down sugars and starch to carbon dioxide) in the field until the haylage or baleage is harvested and deprived of oxygen. Thus, making a wide swath to enhance drying preserves more starch and sugars for the bacteria to produce acids.

This also means that forage lying in the field for more than two days due to rain or poor drying conditions has likely respired much of its starch and sugars. With little substrate, or food, for the bacteria, they will not likely be able to produce much acid. Thus, inoculation is likely to be of little value when forage has lain in a field longer than two days.

In summary, good fermentation helps preserve haylage both in storage and in feedout. Fermentation requires anaerobic conditions, Lactobacillus bacteria well distributed throughout the forage and food for the bacteria. If any one of these three conditions is limiting, poor fermentation will result.

Undersander is a research forage agronomist at the University of Wisconsin.

This article published in the May, 2011 edition of WALLACES FARMER.

All rights reserved. Copyright Farm Progress Cos. 2011.