Weather has the largest influence on grain quality, and grain quality has a direct effect on swine consuming this grain. Grains commonly used in swine diets are subject to fungi-producing mycotoxins, excess nitrates, decreased test weights and storage issues.
Molds may grow on grain during all phases of growth. Aspergillus is a fungi that grows best during periods of drought and grain damage due to hail, birds and insects. Aspergillus produces the mycotoxin Aflatoxin. Fusarium fungi may be produced in corn especially during a cold, wet harvest. Fusarium head blight may infect grain heads when wet weather occurs during the flowering and grain filling stages of plant development.
The occurrence of Fusarium head blight does not automoatically mean that mycotoxins will be present, but a high level of scabby kernels in the harvested grain means mycotoxins will likely be present.
Penicillum is a fungi that will grow on grain used in swine diets also, and it produces a variety of mycotoxins.
Grain moisture content and temperature interact to affect storage risk. Grain quality will not increase during storage; at the most, grain quality can only be maintained. Most damage that occurs during storage is caused by molds and insects.
While the three fungi noted here are the major mold species that grow in feeds, the presence of these fungi does not mean mycotoxins will be produced. However, the potential for growth is there. A “perfect storm” of temperature, moisture and storage time will increase the production of molds.
Reduce the moisture concentration by one percentage point when storing low-quality grain. To reduce the incidence of molds and insects, cool and dry grain immediately after harvesting.
Editor’s Note: Steve Ensley, DVM, PhD is a clinician in the Veterinary Diagnostic and Production Animal Department at Iowa State University, Ames, Iowa.