Inoculants depending on the forage type are designed to preserve the contents of the silage as much as possible for feedout. They do this by lowering the pH to a point where undesirable bacteria, which can lower the quality of the silage, can’t grow. So if the pH of wetter silages (<30%) is lower than pH 4.2 after 72 hours, it’s safe to say the inoculant has worked.
Inoculants also help reduce dry matter losses. If your silage looks like its shrunk when you open and you can see effluent running from it, it’s likely the silage has suffered a poor fermentation resulting in high dry matter and energy losses.
Some inoculants are designed to treat drier forages with high sugar levels. These forages tend to ferment to lower pH readily, but when opened are often very unstable. Yeast and molds grow readily and the silage heats significantly. This results in significant levels of the silage being wasted. If you silage is not heating or no spoilage is seen on the face of the bunker after 3 or 4 days of being exposed to air, it’s safe to conclude that the inoculant has worked.
Read more on how to select forage inoculant.