“How is aerobic stability measured?“
The aerobic stability of silage has become a “hot topic,” and yet this is the first time I have been asked how it is measured or determined!
Typically silage samples are taken from the undisturbed silage mass and are mixed by hand to incorporate air. Then the samples are stored at ambient room temperature, usually in open Styrofoam containers. The initial silage temperature and changes in temperature over time are recorded, preferably using data loggers, though frequent hand testing with a thermometer can suffice.
In most studies, silage is deemed to have lost stability when its temperature is 2 degrees Celsius above ambient temperature as part of a consistent heating event (i.e. not just a “blip”). This increase in temperature is a result from the activity of aerobic microorganisms that started the spoilage process.
Some researchers prefer a 1-degree Celsius increase, some others prefer 3-degree increase, but the 2-degree Celsius standard is most common. There are also other alternatives, such as measuring carbon dioxide production (produced from aerobic growth) or measuring pH increase, but these require more sophisticated equipment and techniques.
By using a standardized method, the stability of a given silage, or TMR, can be compared to the existing database and categorized.
I hope this information helps you understand how aerobic stability is measured and helps you improve the stability on your own feedstuffs.
The Silage Dr.