Molds grow over a temperature range of 50-104°F and a pH range of 4-8. Mold spores are in the soil and in plant debris ready to infect the growing plant in the field or during storage.
Some molds produce mycotoxins under certain conditions, but the presence or absence of mold does not directly indicate the presence or absence of mycotoxins. For example, Fusarium molds have been reported to grow prolifically at 25-30°C without producing much mycotoxin, but at near freezing temperatures they produce large quantities of mycotoxins with minimal mold growth (Joffe, 1986). Molds can be detrimental to animal performance regardless of mycotoxin contamination.
Mold identification can be used to determine which mycotoxins are likely to be present. See the chart below for information on molds and their associated mycotoxins.
|Mold Species - Producing Toxin||Color||Toxin||Conditions favoring production|
|Aspergillus||Yellow-Green||Aflatoxin Ochratoxin||Heat and drought stress pre-harvest Heat and humidity postharvest|
|Fusarium||White to Pinkish-White||
|Grows both pre and postharvest. Excessive moisture during flowering and grain fill of wheat. Cool wet growing season with insect damage. Dry conditions mid-season followed by wet weather. Associated with ear and stalk rot in corn, head scab in small grains, red ear rot, and pink ear rot|
|Penicillium||Green to Green-Blue||Ochratoxin||
Cool, wet, and low pH (acid tolerant) postharvest
|Cladosporium||Dark blue-green to gray or black||None||
Early frost, neutral pH, high grain moisture (30-40%), temperatures at 75-125ºF
|cfu/gram||Feeding Risk and Cautions|
|Under 500,000||Relatively low count|
|500,000 to 1 million||Relatively safe|
|1 to 2 million||Discount energy (x .95) Feed with caution|
|2 to 3 million||Closely observe animals and performance Discount energy (x .95)|
|3 to 5 million||Dilute with other feeds. Discount the energy (x .95) Observe closely|
|Over 5 million||Discontinue Feeding|
a Risks refer primarily to effects of mold per se without regard to possible mycotoxin content. Depressed digestibility, feed intakes, and performance may occur from a high mold content without mycotoxins present. Harmful mycotoxins may be present, even when there is little or no obvious mold content.
b Mold spore counts sometimes may underestimate the degree of mold present, especially in feeds that have been ensiled for some weeks. Observe and record relative amounts of mold present.
Joffe, A.Z. 1986. "Fusarium Species: Their Biology and Toxicology". John Wiley and Sons, Inc. New York.
Kurtzman, C.P., B.W. Horn, and C.W. Hesseltine. 1987. Aspergillus nomius, a new aflatoxin-producing species related to Aspergillus flavus and Aspergillus tamarii. Anton v. Leeuwenhoek 53:147-158.
Adams, Richard S., Kenneth B. Kephart, Virginia A. Ishler, Lawrence J. Hutchinson, and Gregory W. Roth. "Mold and Mycotoxin Problems in Livestock Feeding." Dairy Cattle Nutrition (Penn State Extension). Penn State Extension, n.d. Web. 17 Sept. 2013.
Hoffman, P., R. Shaver, and P. Esker. 2009. High moisture corn, aerobic stability, feed additives, and mycotoxins: Common questions. The 2009 Wisconsin Corn Corp.
Wright, C., B. Holland, R. Daly and L. Osborne. 2009. Moldy corn for beef cattle. SDSU Extension Extra: 2069.