High levels of fungal species and mycotoxins (the toxins produced by some fungi) have been identified in equine feeds. This contamination can result in nutrient losses from the food, and it can negatively impact the health and productivity of horses.

In a study done in 2007 in the journal Veterinary Research Communications by Brazilian researchers from the Federal Rural University of Rio de Janeiro and the National University of Rio Cuarto, 60 feed samples collected from five different locations in Rio de Janeiro were evaluated for both the type and amount of fungi, measured by colony forming units (cfu) per gram of food material. In addition, the concentrations of two mycotoxins were also determined.

The most common fungi identified in this study were Aspergillus, Fusarium, and Penicillium, and the amount of fungi in the feed exceed the proposed limit of 104 cfu per gram.

In contrast, aflatoxin B1 and fumonisin B1, toxins produced by Aspergillus and Fusarium species, respectively, did not exceed acceptable levels as defined by Good Manufacturing Principles Guidelines. Nonetheless, this study suggested that identification of excessive amounts of fungi indicates that the feed is less nutritious.

According to Gary Osweiler, DVM, from Iowa State University, College of Veterinary Medicine, while the ingestion of mycotoxins can be detrimental to horses, the relationship between the presence of fungi or their toxins and the nutritional value of feeds remains controversial. High concentrations of mold spores would be an indication to test a feed for mycotoxins as an added feed safety measure.

“If environmental conditions permit fungal growth, the potential for reduced energy and possibly vitamins is increased; however, the presence of only mycotoxin spores is usually poorly correlated with the nutritional status of the grain or feed,” Osweiler reported.

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