ARTICLE 94 FEED & ADDITIVE MAGAZINE February 2026 Antioxidant systems modulate susceptibility of the epithelial barrier to oxidative stress. Glutathione serves as a primary intracellular antioxidant that neutralizes reactive species and protects tight junction proteins from oxidative modification, supporting maintenance of junctional localization and structure. Nitric oxide signaling contributes to epithelial perfusion and cellular communication under physiological conditions, but dysregulated nitric oxide metabolism promotes RNS accumulation and barrier dysfunction. Nutritional strategies that sustain antioxidant capacity therefore influence whether oxidative stress reaches a threshold sufficient to disrupt tight junction integrity. DDGS AS A POSTBIOTIC FEED INGREDIENT IN DAIRY COWS DDGS contain fermentation-derived residues from yeast and microbes generated during ethanol production, including cell wall-associated polysaccharides and other microbial-associated molecular patterns capable of interacting with host immune pathways and microbial communities. Although DDGS do not deliver live microbes and therefore are not probiotics, they can act as postbiotic-like inputs by supplying microbial-derived bioactive components that influence host physiology. In dairy cows, fermentation products from Saccharomyces cerevisiae have been shown to stabilize microbial ecosystems and attenuate inflammatory responses during rumen and gut stress challenges. These findings support the biological plausibility that fermentation-derived bioactives can modulate microbial dynamics in ways that indirectly support barrier stability. However, DDGS differ from standardized fermentation products in that their composition varies substantially with processing history, storage conditions, and grain quality. As a result, the postbiotic hypothesis for DDGS is strongest when ingredient quality is consistent and does not introduce competing oxidative or toxic stress. QUALITY-DEPENDENT RISK FACTORS LINKING DDGS TO BARRIER DISRUPTION The potential barrier risks associated with DDGS are primarily quality dependent and map directly onto the oxidative mechanisms depicted in the tight junction model. High unsaturated lipid content can increase oxidative load when DDGS are heat damaged or poorly stored, promoting lipid peroxidation and epithelial oxidative stress. Oxidized lipids increase the likelihood of tight junction protein redistribution and cytoskeletal disruption. Mycotoxins represent a second major risk factor. Because DDGS can concentrate mycotoxins from the parent grain, compounds such as deoxynivalenol may be present at biologically relevant levels. Deoxynivalenol is a well-documented epithelial stressor and tight junction disruptor, particularly under concurrent stress conditions such as heat stress or dietary acidosis. Dietary context further modulates risk, as highly fermentable diets and subacute ruminal acidosis shift microbial fermentation and inflammatory signaling, increasing susceptibility to permeability disturbances. QUALITY AND INCLUSION BOUNDARIES FOR POSTBIOTIC PLAUSIBILITY The postbiotic interpretation of DDGS depends on whether fermentation-derived residues are delivered without introducing oxidative or toxic stress sufficient to override barrier-supportive mechanisms. Lipid oxidation provides one functional boundary. Peroxide value serves as a practical indicator, with low values consistent with minimal oxidative burden and values approaching or exceeding approximately 20 mEq O₂/kg fat indicating substantial oxidation that reduces the likelihood of postbiotic-like effects. Mycotoxin contribution represents a second boundary. When DDGS inclusion materially elevates total ration mycotoxin concentrations toward established guidance levels for dairy cattle, barrier disruption mechanisms are likely to dominate, making a postbiotic interpretation biologically implausible. Postbiotic plausibility also depends on inclusion rate. Because DDGS are not standardized fermentation products, sufficient dietary inclusion is required to deliver a consistent quantity of fermentation-derived residues. In lactating cows consuming
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