In this episode of Ruminate This, Scott Zehr is joined by Dr. Larry Roth (VP of Nutrition, Agrarian Solutions) for a discussion about DON (deoxynivalenol/vomitoxin)—one of the most common and most misunderstood mycotoxins in dairy rations.

Rather than causing an obvious crash every time, DON often works like a “pause button” on rumen microbes. It doesn’t necessarily kill bacteria, it slows microbial function and disrupts fermentation, reducing the cow’s ability to convert the TMR into energy and microbial protein. The result can be a quiet, cascading problem: lower feed efficiency, reduced intake, erratic manure, and performance erosion that shows up long after the damage begins.

Scott and Larry discuss how DON can:

• Disrupt rumen microbial balance by interfering with protein synthesis and slowing fermentation
• Push undigested nutrients “down the river” into the hindgut, leading to undesired hindgut fermentation
• Create signs that look like acidosis, when the real issue may be hindgut acidosis driven by poor rumen breakdown
• Weaken gut barrier integrity, increasing permeability and contributing to leaky gut
• Trigger immune activation and force nutrient reallocation, pulling glucose and energy away from milk and reproduction to support inflammation control
• Compound other stressors, making DON a major player in stacked inflammation 

They also discuss why the same DON ppm level can hit two herds very differently, and why ongoing mycotoxin testing can help connect the dots before a slow decline turns into a full-blown crisis.

If you’ve ever wondered, “Is this really rumen acidosis… or something else?” This episode will change how you diagnose digestive, immune, and performance problems in high-producing dairy cows.

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