Introduction

Weather during growing and harvest can increase the possibility of mold and mycotoxin production.  A cool, wet growing season can delay maturity and could result in mold production in the field.  Cool and wet conditions during growth, harvesting, and storage can produce Fusarium toxins.  Aflatoxins are favored during hot and humid conditions.  Drying grains and forages to the optimum dry matter range will help reduce the chances of mold and mycotoxin formation.  However, molds and mycotoxins may still be present after the feed is properly dried and stored.

Mold

Mycotoxins may not always be present in moldy feeds, but the mold itself may cause health and production issues.  Mold may reduce digestibility and the energy content of feeds.  Palatability is also reduced by mold, which reduces intake, resulting in a reduction in energy, dry matter, and other key nutrients.  The reduction in intake of key nutrients can result in reduced performance and immune function.  Mold may cause respiratory issues in livestock and humans due to the mold spores in the air.  If you suspect moldy feed, samples can be submitted to a commercial laboratory for a mold spore count and/or identification.  Table 1 indicates the feed risks of increasing mold spore counts.

Table 1. Feed risks of increasing mold spore counts

Mold count (cfu/g)

Feeding Risk

Under 500,000

Low risk

500,000 to 1 million

Relatively safe

1 to 2 million

Feed with caution

2 to 3 million

Closely observe animals and performance

3 to 5 million

Dilute with other feeds

Over 5 million

Discontinue feeding

This does not account for the mold species present or any mycotoxin production.


Mycotoxins

Mycotoxins may be produced under some conditions that can potentially harm livestock production and health.  Many mycotoxins are regulated by the FDA to limit public health concerns in milk and human food.  Young livestock are more susceptible to mycotoxins.  Several issues can arise if mycotoxins are present, reduced milk production, ketosis, displaced abomasum, diarrhea, rectal or vaginal prolapse, abortion, and reduced conception rates.  Table 2 indicates the mycotoxin concentrations that are limited by the FDA in livestock feeds.

Table 2. Mycotoxin concentrations limited by the FDA.

Mycotoxin

Growing/Finishing

Breeding

Young (<4 mo)

Aflatoxin†

300 ppb

100 ppb

20 ppb

Vomitoxin (DON)‡

10 ppm

5 ppm

5 ppm

Fumonisin*

60 ppm

30 ppm

10 ppm

Zearalenone

  

<10 ppm

<5 ppm (heifers)

  

https://www.fda.gov/animal-veterinary/biological-chemical-and-physical-contaminants-animal-food/chemical-hazards

†Corn and peanut products

‡Grain and grain by-products, no more than 50% of diet

*Corn and corn by-products, no more than 50% of diet

 Conclusion

If molds and/or mycotoxins are suspected, collecting a sample for analysis is crucial.  Feed samples can be submitted to a commercial laboratory for mold count and mold identification.  This mold identification can narrow this list of suspected mycotoxins.  Once molds and mycotoxins, if any, have been identified, a ration can be formulated to meet the needs of the livestock.