Ammonia-N is one of the key indicators of fermentation efficiency. High ammonia-N level (>10% of TN) shows that a good amount of protein has broken down due to poor fermentation. This will reduce the animal performance if forage is not supplemented sufficiently. Good quality fermented forage will usually contain around 5-10% NH3-N. Less than 5% is very good as it indicates very little protein has been broken down.
2. Total Fermentation Acids (% or g/kg DM)
Total fermentation acids (TFA) is mainly made up of lactic and acetic acids and it shows how much carbohydrate has been converted into acids, all of which will help with the acidification. Good fermentation usually results in a TFA of 8 - 12% DM.
3. Lactic acid (% or g/kg DM)
Lactic acid is a key indicator of efficient primary fermentation. Typically, at DM of 25-30%, a good lactic acid fermentation will result in lactic acid content of around 7-10% DM, with the lactic acid comprised of over 80% of total fermentation acids
4. Butyric acid (% or g/kg DM)
If there is presence of butyric acid, this shows that secondary fermentation has occured. It produces a putrid smell, reduces palatability and results in poor quality silage. In an ideal case, silage should not contain any butyric acid although a maximum of 0.5% is acceptable.