Binding zearalenone, from zero to one hundred
Zearalenone is one of the six mycotoxins that pose the highest risk on animal production and profitability. The other mycotoxins are aflatoxin, deoxynivalenol, T-2 toxin, fumonisin and ochratoxin A. As most feed materials are contaminated by more than one of these mycotoxins simultaneously, it is of high importance to apply an anti-mycotoxin feed additive with broad spectrum activity. Due to the wide variation in nature of these mycotoxins, different strategies have to be combined in order to tackle each of them efficiently. In this article, more insight is provided in how zearalenone can be tackled by adsorption.
The mycotoxin 'zearalenone'
The mycotoxin zearalenone (ZEA) is mainly produced by fungi belonging to the Fusarium species which typically grow on crops pre-harvest. After ingestion by the animal, ZEA is easily absorbed in the gastrointestinal tract (80-85%) and distributed throughout the body. Main target organ of ZEA is the reproductive system because of the similarity in chemical structure between ZEA and estradiol, a principal hormone produced by the ovaries. ZEA typically occupies estrogen receptors in the uterus, mammary glands and liver disturbing the normal hormonal processes. Symptoms due to ZEA are reproductive disorders such as embryonic death, increased number of inseminations and lower hatchability.
Generally speaking, 3 strategies are typically combined in an anti-mycotoxin additive to counter negative effects on animal health and performance: adsorption, biotransformation and indirect support to maintain health. Although all three strategies contribute to protection of the animal, direct action against mycotoxins by adsorption should always be maximally employed. After all, if we can remove most of the mycotoxins from the gastro-intestinal tract in their original form, and thus prevent absorption, we maximally reduce the risk on any negative effects.
Overall, two broad categories of mycotoxin binders can be defined: inorganic binders (based on silica) and organic binders (based on carbon) (Figure 1).
Inorganic binders are divided in silicates and other materials such as charcoal. Charcoal is the most effective mycotoxin binder but its use in feed is not practical as it binds nutrients such as vitamins and minerals. Silicates are divided into two classes according to their structure. Phyllosilicates consist of a layered structure like the sheets of a book, tectosilicates have a framework structure. Within one class, minerals have similar chemical characteristics although they can differ in parameters such as number of layers, space between layers, cation exchange capacity, concentration of cations, swelling capacity. Most used organic binders are yeasts or components thereof.
Efficacy of ZEA adsorption
Adsorption of mycotoxins depends on the physical and chemical characteristics of the mycotoxin binder (charge, size of pores, adsorption surface…) as well as of the mycotoxin (polarity, solubility, size, shape…). Overall, the binding efficacy increases with increasing chemical affinities between adsorbent and mycotoxins. Besides characteristics of binder and mycotoxin, other parameters such as the environmental pH have an influence on total binding efficiency.
A wide range of scientific studies have been performed to evaluate the effectiveness of binding agents in adsorbing ZEA. In a study comparing commercially available mycotoxin binders, De Mil et al. (2015) found that products based on yeast cell walls, sepiolite, zeolite, clinoptilolite and mica were much less effective compared to products based on montmorillonite (smectite). However, also within the class of binders based on montmorillonite (practical name = bentonite) a wide variation in binding efficacy could be found ranging from 0 up to 100%. Research conducted by Fruhauf et al. (2012) on the other hand has shown higher adsorption rates of ZEA by yeast based products (up to 60%), while binding was lower for products based on standard bentonite.
Previously described research perfectly shows the wide variety in binding efficacy between and within the different mycotoxin binder classes. Always keep in mind that mycotoxin binders, clays as well as (components of) yeast, are natural products and differ largely depending on the origin and the possible treatment (e.g. purification) they have been exposed to. Comparing anti-mycotoxin additives under the same experimental conditions can reveal lots of information about the true binding efficiency of products towards zearalenone.
Optimal binding by Vitafix®
Nuscience thoroughly evaluated a wide range of mycotoxin binders in the development of highly effective anti-mycotoxin additives. The resulting Vitafix® product range consists of Vitafix® Select, Plus and Ultra. Vitafix® Select consists of bentonites with a focus on binding aflatoxin. Vitafix® Plus and Ultra on the other hand consist of a blend of carefully selected bentonites with high broad spectrum binding efficacy.
An in vitro binding essay was conducted by Trilogy to compare the binding efficiency of Vitafix® Ultra with products of two of the strongest players in the market. One product mainly consists of yeast-based components, the other product is based on both bentonite and yeast. Binding efficiency was determined as the adsorption percentage at pH 6 minus desorption at pH 2 and 8. In this way, the pH in the gastro-intestinal tract of cattle was simulated. The results (figure 2) clearly show the outstanding binding efficiency of Vitafix® Ultra towards zearalenone.
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Article made possible through the contribution of Nuscience Group