Aerobic spoilage during storage is responsible for the majority of dry matter (DM) lost in silage, and losses may be as high as 30% to 40%.
Unfortunately, there’s so single solution to avoid spoilage. Management practices that reduce exposure to oxygen are the best solution to reducing aerobic spoilage, such as:
- Rapid silo filling
- Good packing
- Rapid covering and sealing
- Adequate feedout rates
- Consuming feeds within a few hours after removal, especially during warmer weather
- Using research-proven silage inoculants
Management practices generally do not eliminate yeasts but reduce their ability to grow.
Causes of Instability
Aerobic instability is usually due to rapid growth of yeasts over a short period of time. Even crops harvested at the optimal maturity, moisture content and chop length can be susceptible.
Aerobic spoilage can occur shortly after harvest while there is still oxygen present in the plant mass. Yeasts can multiply during the first few days after harvest, before all of the oxygen in the ensiled feed is consumed. In addition, the crop may ferment well and reach a low pH, only to heat rapidly and spoil at feedout.
The risks for aerobic spoilage can increase when:
- Plants are harvested at increasing maturity levels
- Crops are damaged from hail, insects or frost
- Plants are stressed from drought, for example
- Crops are ensiled with greater than 1,000,000 (1 x 106) colony-forming units (CFUs) of yeast per gram of fresh forage
Corn silage, cereal silages and HMC can have high indigenous yeast populations because yeasts grow best on feeds that contain starch and soluble sugars. Aerobic instability in silage also may allow molds and other opportunistic microbes to grow.
Managing Aerobic Spoilage
Once aerobic spoilage has occurred, organic acids — propionic, acetic and benzoic acids — can be applied to control aerobic instability. There are two common strategies:
- Apply high rates of the acid to achieve complete preservation. To be effective, 10 to 20 lbs., or 4.5 to 9 kgs, active ingredient (AI) of organic acids are required per ton of feed ensiled.
- Apply organic acids at low rates (2 to 5 lbs., or 1 to 2.2 kgs, AI per ton) at ensiling to control yeast populations at feedout.
Lower rates do not provide full preservation, and the material is still dependent on an ensiling fermentation. An inoculant is still recommended to help ensure adequate fermentation.
Don’t Feed Spoiled Silage
Do not feed spoiled silage to livestock. Including spoiled silage in a ration has been shown to lessen animal intake and production. Don’t compromise a carefully crafted ration with spoiled silage. The drawbacks far outweigh any perceived benefits.