Mycotoxins in ruminant nutrition
Part 4: Mitigating mycotoxin challenges
Mycotoxin exposure in ruminant animals is an ubiquitous threat that is often overlooked and underestimated
By Cathy BandykStandard procedures for dealing with mycotoxin-infected feed include dilution with other feedstuffs, and targeting usage to less-susceptible classes of animals. There are also a wide array of mycotoxin mitigation products available globally. However, because there is not an FDA-approved classification for toxin binders, no market claims for that usage can be made in the U.S. And, as with any other non-medicated additive, their use cannot be supported in this country with direct health or performance claims. With that said, the efficacy of many of these tools have been tested both here and abroad.
This is the final part of a 4-part series.
Products utilized in response to mycotoxin challenges may contain ingredients that (a) physically bind or adsorb to certain compounds, preventing them from exerting negative impacts prior to excretion; (b) modify or deactivate toxins into benign or minimally hazardous derivatives; and / or (c) provide support or remediation of mycotoxin-induced symptoms (e.g., liver damage, oxidative stress). Common sequestration agents include various clays and silicates as well as yeast or yeast-based products.
An in-depth review of individual binders or products is beyond the scope of this article. However, there are a number of key takeaways that stand out in the literature. Numerous clays have been shown to be effective at reducing the transfer of dietary aflatoxin and its metabolites into milk (Queiroz et al., 2012; Maki et al., 2017; Sulzberger et al., 2017; Rodrigues et al., 2019), but they may be less effective with other toxins. Also, Queiroz and co-workers found that while the clay binder they were testing reduced aflatoxin in milk by 24%, it did not offset the observed toxin-induced increase in innate immune response. Feeding rate, or possibly the ratio of binder:toxin (Kihal et al., 2023), is critical; Maki and Sulzberger reported linear responses to increasing doses of binder, although in the latter study the highest level fed resulted in a reduction in milk yield and feed efficiency. It is equally important to match dose of yeast MOS (mannanoligosaccharide) products to level of mycotoxin exposure (Xiong et al., 2015).
A direct comparison of four yeast-based products – autolyzed yeast, yeast cell wall, brewer’s yeast, and active dry yeast – again using milk aflatoxin concentration as the primary response indicator, clearly showed that these interventions are not equally effective (Gonçalves et al., 2017). They reported reductions in milk AFM1 of just 45% for dry yeast and 50% for brewer’s yeast, and 78% and 89% for cell wall and autolyzed yeast, respectively. The sequestration activity of yeast is due primarily to beta-glucans found in the cell wall (Jouany et al., 2004). Depending on the specific mycotoxin they come in contact with, these complex polysaccharides may form hydrogen, hydroxyl, van der Waals, polar, or electron bonds, inhibiting toxigenic impacts through binding or adsorption. Their exact structure, and therefore efficacy, is dependent on yeast strain, culture conditions (pH, temperature, oxygenation, growth medium), the point in the cell cycle they are harvested, and, as seen in the Gonçalves work, processing of the yeast to expose the cell wall components.
Commercial mycotoxin remediation products may contain multiple binders as well as enzymes and/or various phytobiotics to broaden their effectiveness. A specific enzyme has been identified, for example, that redirects the metabolic pathway for ingested ZEN, resulting in creation of a non-estrogenic metabolite rather than the highly potent zearalenol (Gruber-Dorninger , 2021). There is a large body of information describing the bioactive effects of various plant essential oils and extracts, with potential applicability to mycotoxicosis. Those with demonstrated anti-oxidant, anti-inflammatory, immune-modulating, hepatoprotective, and intestinal support properties offer opportunities for minimizing health challenges and production losses. In their review, Jiang and co-authors emphasized the value of combining antioxidants with binders (Jiang et al., 2021). Additional research is clearly needed to evaluate effectiveness of various product components and combinations, identify ingredient characteristics that impact their effectiveness, and determine optimal dosing strategies. On-farm, the use of biomonitoring, with direct animal exposure measurements taken before and after implementation of a remediation program, can provide valuable site-specific insight into efficacy.
Conclusions
Mycotoxin exposure in ruminant animals is an ubiquitous threat that is often overlooked and underestimated. Historic approaches to evaluating both risk and exposure have provided an incomplete picture of this inherent challenge to animal health and performance. Recognition of all potential toxin sources and consideration of a broader range of compounds, combined with better understanding of testing limitations, can improve assessments. Use of biomarkers as indicators of actual animal exposure, while not yet widely available, can offer highly credible insights. Guidelines for determining “safe levels” of individual mycotoxins need to consider the implications of chronic low-level intakes and co-exposure to multiple toxins and other stressors. Evaluation of remediation tools should include range of actions, ingredient form and consistency, and demonstrated effectiveness under natural contamination conditions.
References available upon request.
Cathy Bandyk, PhD, PAS, is Technical Development Manager with Innovad, a provider of animal nutrition and health solutions.
