Raquel Marques1and Graziela Valini2
¹Ruminant Technical Specialist, ²R&D Specialist, ICC Animal Nutrition
A hidden challenge in modern dairy production
Mycotoxins are toxic secondary metabolites produced by certain fungi that may contaminate maize, small grains, oilseed meals, silages and other dairy cow feed ingredients . Visible mold is not a reliable diagnostic sign, because apparently normal feed may contain mycotoxins, while moldy material does not reveal which toxins are present or at what concentration. Contamination may begin in the field during drought, heat, insect damage or excessive rainfall and intensify during harvest, storage or silage feed-out. In tropical and subtropical dairy systems, such as thoseinIndia, high temperatures, seasonal humidity and long storage periods can further increase exposure.For the dairy cow, the consequences extend beyond feed quality, as mycotoxins may reduce dry matter intake, alter rumen fermentation, impair nutrient utilization, disturb liver function, weaken immune responses, and compromise reproduction. These effects are often subclinical and may appear as inconsistent milk yield, lower milk components, poor conception or greater diseasesusceptibility . Because these signs overlap with heat stress, subacute ruminal acidosis, poor silage fermentation and transitionperiod disorders, exposure can be difficult to recognize. A total mixed ration may contain several contaminated ingredients, with toxin profiles varying between batches or silosections . Effective control therefore depends on prevention, monitoring and knowledgeof how major mycotoxins behave in ruminants.Why mycotoxin chemistry matters
Mycotoxins differ in polarity, molecular size, shape, solubility and electrical charge,and these influence absorption and interaction with mineral or organic sequestrants. Relatively polar compounds, such as aflatoxins, generally have a greater affinity for selected aluminosilicate , whereas less polar compounds, such as zearalenone (ZEA), may interact more effectively with organic matrices such asyeast cell-wall (YCW) . Polarity alone, however, does not determine efficacy. Pore size, accessible surface area, cationexchange capacity, pH, molecular conformation and the stability of the toxinadsorbent complex are also important.
This explains why a single-component binder may perform well against one toxin but offer limited protection against another. Dairy cattle are also more likely to face mixed contamination than a single toxin. Although the rumen can convert certain mycotoxins into less harmful metabolites, this capacity is neither uniform nor unlimited. Its effectiveness depends on the toxin,ruminal pH, passage rate, diet composition, and microbial stability. Consequently, high-producing cows exposed to several mycotoxins may remain at risk despite partial ruminal degradation, andsupporting mitigation strategies that consider both toxin chemistry and the cow’s physiological status are needed.
The most relevant mycotoxins in dairy herds
Aflatoxin B1 (AFB1), produced mainly by Aspergillus species, is important because it threatens animal health and milk safety. After ingestion, part of AFB1 is absorbed and metabolized in the liver into aflatoxin M1 (AFM1), which can be excreted in milk. Aflatoxin exposure may reduce feed intake and milk production, impair immune competence and cause liver damage AFM1 is a public-health concernbecause the International Agency for Research on Cancerclassifies it as possibly carcinogenic to humans. It may also be detected in milk without obvious clinical signs, making control of AFB1-contaminated feed essential.
Zea, produced mainly by Fusarium fungi, can interact with estrogen receptors and is therefore closely associated with reproductive disorders. Exposed cows may show irregular estrous cycles, reduced conception, embryonic loss or other signs of endocrine disruption. Because these outcomes mayalso result from negative energy balance, heat stress or poor reproductive management, the use of mycotoxin bindersbecomes essential. Deoxynivalenol, or DON, is another frequent Fusarium contaminant. Adult cattle can convert part of DON into less toxic metabolites in the rumen;however prolonged exposure may still reduce feed intake, alter rumen fermentation, impair intestinal integrity, and affect immune and metabolic responses.
Fumonisins, especially fumonisin B1, are commonly associated with maize-based feeds. They interfere with sphingolipid metabolism and mainly affect the liver and immune system, contributing to hepatic stress, inflammation, and poorer nutrient utilization. T-2 and HT-2 toxins inhibit protein synthesis and may damage rapidly renewing tissues, including the gastrointestinal epithelium, while ochratoxin A is mainly nephrotoxic. Although the rumen can degrade part of ingested ochratoxin A, protection may decline under high exposure or disturbed rumen conditions. Risk assessment should therefore consider the toxin profile and co-contamination, not only the total concentration detected.
From prevention to targeted mitigation
The first line of defense is prevention. Good agronomic practices, timely harvest, adequate drying, effective ensiling, oxygen exclusion, careful silageface management and hygienic storage help limit fungal growth and toxin production. Even well-managed systems, however, cannot completely eliminate contamination, particularly because mycotoxins are distributed unevenly within silos, grain lots and feed batches. Representative sampling and laboratory analysis are essential, andresults should be interpreted alongside dry matter intake, milk yield and composition, manure consistency, reproductive performance, transition-cow health,addisease incidence.
When exposure cannot be fully prevented, mycotoxin binders provide a second level of protection. Their role is not to make visibly spoiled feed acceptable, but to reduce the bioavailability of toxins remaining in the ration. Because mycotoxins differ in polarity, size and structure, effective mitigation generally requires more than one mode of action. Hydrated sodium calcium aluminosilicate (HSCA), for example, is particularly relevant for relatively polar compounds such as AFB1. After hydration, its lamellar structure expands, exposing charged sites capable of interacting with toxin molecules. Cation exchange, porosity and surface characteristics favor toxin–mineral complexes, reducing absorption and promoting fecal elimination. Mineral adsorption can be complemented by the cell wall of Saccharomyces cerevisiae. YCWs contain β-1,3- and β-1,6-glucans and mannan-oligosaccharides, which provide a chemically diverse surface capable of interacting with mycotoxins through hydrogen bonding, and hydrophobic interactions. This is relevant for compounds that bind poorly to minerals because of lower polarity or complex geometry.
For example, YCW effect was demonstrated in a Journal of Dairy Science study involving lactating Holstein cows exposed to 480 µg of AFB1 per day. An ethanol-derived YCW fraction supplied at 20 g per cow per day reduced milk AFM1 concentration by 78%. This evidence shows that a selected S. cerevisiae cell-wall fraction can reduce AFB1 bioavailability and carryover into milk, complementing mineral adsorption.
StarFix® within an integrated mycotoxin-control program
Preventive management, mineral adsorption and YCW binding provide the rationale for integrated solutions targeting prevalent mycotoxins in dairy rations. StarFix® was developed by ICC Animal Nutrition as a multi-component mycotoxin binder for ruminant diets. Its formulation combines HSCA, YCW derived from sugarcane-ethanol S. cerevisiae, and nucleotides. HSCA provides high-affinity adsorption for relatively polar toxins, while YCW broadens molecular interactions through its β-glucan- and mannan-rich structure. Together, the mineral and organic fractions increase the opportunity to sequester toxins with different chemical characteristics before absorption.
Additionally, nucleotides address a different aspect of the mycotoxin challenge. Although they are not direct toxin binders, they are functional nutrients involved in DNA and RNA synthesis, cellular signaling, and energytransfer reactions. Cattle can synthesizenucleotides through the de novo pathway in low amounts;however, supplementing dietary nucleotides and nucleotide bases are more readily available substrates to tissues with high cellular turnoverthrough salvage pathway, with lower metabolic costs. This approach is especially relevant for the intestinal epithelium and liver, which play central roles in barrier integrity, toxin metabolism and the response to exposure.
Therefore, combining HSCA, YCW and nucleotides, StarFix® supportthree objectives: reducing the intestinal availability of toxins, broadening molecular interactions across toxins of different polarity, and providing nutritional support to tissues involved in metabolism and recovery. It should be used as part of a complete programthat begins with feed-quality management and representative testing.
A broader view of mycotoxin control
Mycotoxin management in dairy herds should not be reduced to whether a binder is included in the ration. Effective programs combine crop and storage management, representative testing, herd performance assessment, and strategic anti-mycotoxin technologies. Attention should extend beyond AFB1to Zea , DON, fumonisins, T-2 toxins and ochratoxin A, because co-contamination is common and different toxins affect different organs and production outcomes.
Within this framework, StarFix® represents one practical option for addressing prevalent mycotoxins through the complementary actions of HSCA, selected ethanol-YCW and nucleotides. The reduction in AFM1 excretion observed with YCW in lactating cows illustrates why the quality and processing of the organic component matter. Nevertheless, no additive can replace good feed hygiene or correct storage. The objective is to reduce exposure, preserve rumen and intestinal function, support liver health, limit aflatoxin residues in milk, and minimize harmful effects. Treating control as an integrated process allows dairy producers to better protect animal health, reproductive efficiency, milk production and food safety.