Trial shows delayed sealing’s negative impact on forage quality

By Michelle Chang-Der Bedrosian, Ph.D., Vita Plus
The initial phase of making silage is the aerobic phase and it is characterized by the presence of oxygen.  The aerobic phase begins when the plant is cut in the field and continues until the silo is sealed (either the plastic is laid on top of the silo or the bag silo is sealed) and oxygen is consumed by the upfront fermentation.  During this aerobic phase, the plant and the epiphytic microbes are still alive.  These microbes consume available high-quality proteins and water-soluble carbohydrates.

The danger of this process is that forage quality is related to protein and sugar content; anything that prolongs the aerobic phase decreases silage quality.  Fermentation is the conversion of sugars into acids that decrease the pH of the forages, which in turn protects the crop against microbial degradation.  The faster the pH declines, and the lower the pH becomes, the better silage quality.

When the aerobic phase is prolonged, such as with delayed sealing, valuable sugars are consumed and are therefore not available for fermentation.  Silages that have delayed sealing (24 hours or more) have a higher pH and less lactic acid because of this decrease in sugars for fermentation.  As a result of the higher pH, there is often more clostridial fermentation, which results in more butyric acid and more DM losses.

Graph 1. Effect of delayed sealing on silage pH.

Graph 2. Effect of delayed sealing on butyric acid production.

A recent trial ensiled 26% DM triticale in an effort to simulate a difficult-to-ensile crop.  Silages were stored in 2-gallon bucket silos that were treated with various bacterial inoculants – untreated, Crop-N-Rich^® MTD/1^® or an experimental inoculant – and sealed either immediately or after 24 hours (delayed sealing).

Results from this trial highlighted:

• Delaying sealing of silages for 24 hours, even though the silos were packed to a good density, resulted in a higher pH and less lactic acid.
• Inoculating the silages with a high-quality inoculant, such as Crop-N-Rich MTD/1, decreased the pH well compared with untreated silages and was a successful treatment to prevent the growth of Clostridia and production of butyric acid.
• Inoculating the silages with Crop-N-Rich MTD/1 did overcome the challenge of delayed sealing, underscoring the value of inoculants as an insurance policy should there be management challenges.
• In silages that had a higher pH, either due to a lack of inoculation or delayed sealing, there were higher levels of butyric acid.

It is important when discussing delayed sealing to underscore the value of safety, especially during or at the end of harvest. Employees are tired in the last stretch of the race.  Exhaustion, weather and loss of daylight can increase the danger associated with covering a pile.  Human lives are much more important than silage quality.  Silages should be covered as soon they can be by well-rested employees who are able to see clearly.  No tombstone will ever say “but the silage quality was great!”  Cover silages promptly, but make safety the first priority.