Mycotoxins and Ruminants: Everything You Need to Know

What are mycotoxins and where do they come from?

Mycotoxins are potentially toxic compounds or metabolites produced by fungal mold spores. The molds are produced from fungi found in the field (pre-harvest contamination) or in storage (storage contamination) environments.

Did you know that fungi consists of molds, yeasts and mushrooms?

The prevalence of mold is highly dependent on weather conditions (moisture), naturally occurring fungal population, and substrates for growth…

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Mycotoxin contamination can vary dramatically from year to year due to the wide fluctuation in weather patterns. Mycotoxins occur frequently in a variety of feedstuffs and are routinely fed to animals. Sometimes, mycotoxins occur at concentrations high enough to cause major losses in health and performance of animals.

However, a more likely scenario is to find mycotoxins at lower levels interacting with other stressors to cause subclinical losses in performance, increase incidence of disease and reduced reproductive performance. These subclinical losses can represent a greater economic loss than from acute effects but they can be more difficult to diagnose.

What happens when a ruminant consumes mycotoxins?

Vomitoxin and zearalenone are widely distributed in Canadian feedstuffs with lesser amount for T-2 toxin. Chronic exposure to mycotoxins can lead to: decreased DMI, reduced milk production, impaired reproductive performance and suppressed immunity.

What happens in the rumen?

Rumen function can be negatively affected by the presence of mycotoxins, suggesting a signifi cant role of the rumen in handling mycotoxin exposure, biotransformation and excretion of metabolites. The negative effects can include decreased fi bre degradation, altered VFA (energy by-product of rumen function) production, altered ammonia production and decreased proteolysis.

During the biotransformation process, the resulting rumen metabolite can change in toxicity from the original toxin. Aflatoxin is bio-transformed to afl atoxicol (similar toxicity). Vomitoxin is bio-transformed to de-epoxy-DON which is less toxic. Zearalenone is bio-transformed to a-zearalenol which is more toxic.

What are mycotoxin adsorbents?

Mycotoxin adsorbents are ingredients that sequester or bind mycotoxins to help prevent toxicity in the gastro intestinal tract and to prevent absorption across the gut wall. The adsorbent acts like a “chemical sponge” when the surface of these materials are saturated with water by attracting polar functional groups of mycotoxins. The “bound” toxins are then eliminated in the faeces, thus preventing any deleterious effects on the dairy animal.

Mycotoxin binding is achieved through both physical and chemical adsorption (ionic or covalent bonding). Mycotoxin adsorbents fall into two broad categories – Inorganic and Organic.

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Inorganic Adsorbents

The inorganic adsorbents are typically composed of inert, inorganic silicate clays
broadly categorized as aluminosilicates. Inorganic binders are further classified according to their physical structure; predominantly phyllosilicates (sheet structure) and tectosilicates (3-dimensional structure).

The sheet structure (phyllosilicates) category consists of clays such as bentonite (sodium and calcium) and smectites (HCAS and Montmorillonites). They have a high Cation Exchange Capacity (CEC) that allows binding of polar molecules in the layers. The 3-dimensional clays (tectosilicates) or zeolites contain large crystalline pore structures (similar to a honey-comb structure) that acts like a molecular sieve.

Organic Adsorbents

The primary organic adsorbents used in animal agriculture for toxin control are extracts of yeast cell walls. Yeast cell wall extract is produced from Saccharomyces cerevisiae yeast that has gone through successive centrifugations and then completed by a specific enzymatic treatment. This process will produce a consistent supply of mannans (MOS) and ß-glucan.

Yeast cell wall extract which contains both mannan (MOS) and ß-glucan have been shown to be an effective binder for a variety of mycotoxins. The ß-glucans have been shown to bind zeralenone through a glucansmycotoxin binding process. The carbohydrate component of the yeast cell wall extract provides different binding sites for different toxins.

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Recommendation for Adsorbents

Because of the diffi culty to determine the levels of all mycotoxins in feedstuffs, a broad approach for mycotoxin adsorbents is recommended. Plus different inorganic and organic binders will have different mechanisms and sites for binding different mycotoxins.

Using a variety of aluminosilicate ingredients with a consistent, high quality yeast cell wall extract will deliver the broadest coverage.