Butyric Acid

The main source of butyric acid in silage is fermentation by clostridia, which are present on the crop in relatively small numbers at harvest. Numbers in the ensiled forage can be dramatically increased by the inclusion of soil, picked up either by cutting the crop too low or during raking or tedding, or on packing tractor wheels in wet conditions. Soil can contain up to 10 billion CFU of clostridia per gram. In addition to producing butyric acid, which can give the silage a very strong, persistent fecal smell, clostridia can also break down proteins, leading to significant loss of protein and the production of biogenic amines, e.g. histamine, putrescine, cadaverine, that can affect herd health and/ or production and produce odors associated with putrification or decay.