Nutritionist > Pig
Fungal growth
Fungal species are often divided into two groups:
- Field fungi
- Storage fungi
Storage fungi (also called storage moulds) are those that invade grains or seeds during storage. They need less moisture than field fungi (13-18%) and usually do not present any serious problem before harvest. Storage fungi include species of Aspergillus and Penicillium.
While the field/storage terminology is generally used to indicate the differences in temperature and moisture required by various fungi, the proper conditions for the growth of a specific organism can occur in either the field or storage bin. Ideal conditions for fungal growth depend on the species, but normally moulds require high temperature and moisture.
Mycotoxins are produced as secondary metabolites. Under field conditions, stress and subsequently reduced vigour often predispose plants to infestation and colonisation by toxigenic fungi. In stored grain, toxigenic fungal infection and mycotoxin production result from a complex interaction between moisture, temperature, substrate, oxygen (O2) and carbon dioxide (CO2) concentration, fungal abundance and insect presence. Insects can influence a differentiation of fungal species, that is a specific insect determines the presence of a specific fungal species.
Mycotoxins can be found in forage. On one side plants can modify the concentration of mycotoxins due to different enzymatic systems. On the other side, it seems that they can move substances from the site of production to the hull and the stem and then to the leaves.
In general, most fungi need at least 1-2% oxygen and usually grow at temperatures between 20 and 30°C. It is important to note that if the grain is at high temperature at harvest, it can maintain that high temperature for several days or weeks after harvest unless the storage facility has cooling capabilities. Normally, in storage conditions fungi grow at 13-18% moisture. However, in case of grains with high levels of oil (e.g. peanuts) fungal growth occurs at moisture contents as low as 7%.
