Mycotoxins are toxic compounds produced by mold growth in feed ingredients. The most significant mycotoxins affecting swine are aflatoxin, vomitoxin, zearalenone, fumonisin, and ochratoxin, which are produced by molds that belong to the genera Aspergillus, Fusarium, and Penicillium. Mycotoxin contamination prevention includes pre- and post-harvest strategies. Interventions carried out in the field to prevent fungal infestation, such as crop rotation, tillage, insect control, and fungicides, are the most effective but often insufficient to prevent mycotoxin contamination (Jard et al., 2011). After harvest, one effective intervention is to screen and clean grain to reduce mycotoxin contamination in grains (Yoder et al., 2017). The most prevalent intervention is the inclusion of mold inhibitors and mycotoxin binders in the feed (Vila-Donat et al., 2018).
Mold inhibitors are used to control mold contamination and prevent mold growth in order to minimize the risk of having proliferation of mycotoxin-producing molds in grain or feed (Jacela et al., 2010b). Acidifiers are commonly used as mold inhibitors, particularly organic acids such as propionic acid. Acidifiers display fungicidal properties by reducing the pH in grain and feed (Suiryanrayna and Ramana, 2015). However, the use of acidifiers as mold inhibitors have no effect on mycotoxins already present in contaminated grain and feed (Jacela et al., 2010b).
Mycotoxin binders or adsorbents are substances that bind to mycotoxins and prevent absorption through the gut (Table 1). The most commonly used mycotoxin binders in swine feeds are aluminosilicate binders, which include clays, bentonites, zeolites, and hydrated sodium calcium aluminosilicate (HSCAS). The aluminosilicate binders are natural, inorganic mycotoxin binders containing a porous structure made of silica that is able to adsorb and trap mycotoxins (Jouany, 2007; Di Gregorio et al., 2014). The aluminosilicate binders are very effective aflatoxin binders, but have limited activity against other types of mycotoxins (Huwig et al., 2001; Jiang et al., 2012; Vila-Donat et al., 2018). Furthermore, aluminosilicate binders are nonspecific and bind vitamins and trace minerals as well (Huwig et al., 2001; Vila-Donat et al., 2018).
Other mycotoxin binders used in swine feeds are yeast components. The yeast components are natural, organic mycotoxin binders extracted from the cell walls of Saccharomyces cerevisiae, primarily α-mannans and β-glucans (Jouany, 2007). The yeast components have a diverse mechanism of adsorption and act against a wide range of mycotoxins (Huwig et al., 2001). Furthermore, organic yeast components are biodegradable and do not accumulate in the environment after being excreted in the manure, in contrast to inorganic silicate binders (Jouany, 2007).
However, mycotoxin binders are vastly ineffective against vomotoxin (Dänicke, 2002; Döll and Dänicke, 2003; Frobose et al., 2015). Vomitoxin is the colloquial term for deoxynivalenol (DON), the most common contaminant of grains and feed (Rodrigues and Naehrer, 2012). Recently, sodium metabisulfite has been found to be a promising agent against vomitoxin (Frobose et al., 2017; Shawk et al., 2018). Although not approved by Food and Drug Administration as a DON-detoxifying agent, sodium metabisulfite reacts with DON to form a non-toxic component in a process that requires heat and humidity for optimal efficiency (Young et al., 1987). The addition of sodium metabisulfite to diets naturally contaminated with vomitoxin seems to restore feed intake and improve growth performance of nursery pigs (Frobose et al., 2017; Shawk et al., 2018). However, sodium metabisulfite is known to degrade the vitamin thiamin, which needs to be supplemented in diets with sodium metabisulfite.