Fusarium mycotoxins and horses
By Susan L. Raymond, Equine Research Centre, Trevor K. Smith and Swamy Haladi,
Department of Animal and Poultry Science, University of Guelph

Each harvest season seems to bring a variety of challenges that horse owners and farmers need to address. Cool wet climatic conditions during the harvest season for grain and hay crops increases the likelihood that fungi such as Fusarium can grow in or on these plants. Cattle, pig and poultry farmers are well aware of the potential problems that these fungi and their metabolites can cause in their livestock. Very little research has been completed in Canada on the potential impacts of the various fungi and their mycotoxin metabolites on horse health. In addition, there is a wide range of acceptable levels for the various mycotoxins.
Two research initiatives at the University of Guelph are ongoing to better understand fungal mycotoxins and the impact on horse health. This research update summarizes a project on the effectiveness of a commercially available mycotoxin binder. Feed manufacturers regularly monitor mycotoxin levels in grain and commonly add mycotoxin binders to feed to reduce the potential impact of mycotoxins should they be present in the grain.
Dr. Bob Wright, Veterinary Scientist, Ontario Ministry of Agriculture and Food.

Mould infestation of grain and forage plants usually begins pre-harvest. This is greatly influenced by weather conditions and is difficult to control. Mould growth can be compounded by improper storage postharvest, and can alter the nutritional status of horse feed.

This study looked at the impact of Fusarium moulds on feed consumption. Fusarium moulds are commonly found in temperate climates like Ontario, and mycotoxins
produced by these moulds have a very high economic impact as grain contaminants. The Fusarium mycotoxins are associated with decreased feed consumption, gastrointestinal
disorders and immunosuppression in other livestock species. The horse industry is questioning the effect Fusarium may be having on their horses’ performance or breeding ability and, in particular, the dangers that may be inherent with the chronic consumption of low levels of these mycotoxins.

In response to these concerns, this study was conducted to measure the effect of feeding naturally contaminated grains on feed intake and blood responses in the horse, and to measure the efficacy of a natural nutritional supplement in preventing the intestinal
absorption of feed-borne mycotoxins.


• The feeding of contaminated grains significantly reduced feed intake compared to controls (please refer to figure 1).
• Supplementing with yeast cell wall polymer significantly improved feed intake compared to the feeding of contaminated grains without supplementation.
• Consumption of forage was not affected by diet.
• Serum activities of gamma-glutamyltransferase (liver enzyme) were significantly higher in horses consuming contaminated grains for 7 and 14 days, but not for 21 days.
• Serum gamma-glutamyltransferase activities were not affected by the feeding of contaminated grains containing the yeast cell wall polymer.

Management Methods and Conclusions:

It was concluded that the feeding of grains naturally contaminated with Fusarium mycotoxins altered serum chemistry in mature horses and significantly reduce feed
intake. Supplementation of yeast cell wall polymer to contaminated grains was beneficial in alleviating reduced feed intake in these horses.

Mycotoxins are very difficult to get rid of once formed and few effective strategies to eliminate them have been identified. Controlling exposure to mycotoxins begins by controlling mould growth from point of harvest and maintaining low mould growth throughout storage up to and including feeding. Forage and grain should be processed at low moisture content. Grain should be kept intact until adequately dried. Mould growth is more prevalent in damaged or processed grains. Mycotoxin adsorbents (yeast cell wall polymer) can be used when mycotoxin exposure cannot be avoided.

The authors would like to acknowledge the generous support of the Ontario Horse Racing Industry Association, Rural Job Strategy Fund and Alltech Inc. The authors would also like to acknowledge the contribution of our research horses.

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Updated: October 2005.