Multiple mycotoxins in the TMR do not just add up. They multiply damage in dairy cows.
In this episode of Ruminate This, Scott Zehr and Vice President of Nutrition Dr. Larry Roth connect their previous episode discussions and explain why multiple mycotoxins in the TMR create a multiplying negative effect in dairy cows rather than a simple additive one.
They discuss how common toxins such as DON, fumonisin, T-2/HT-2, and zearalenone each remove a critical layer of biological protection. Even when individual toxin levels appear “safe,” combinations can lower the cow’s ability to defend herself, regulate intake, maintain rumen integrity, and support reproduction.
The episode explores high-risk toxin pairings, early warning signs such as inconsistent intake, erratic manure, milk production plateaus, and reproductive challenges, and why multiple low-level mycotoxins are often more dangerous than a single high-level exposure.
🎧 Listen now to set your herd up for lifelong success!
Scott Zehr: All right. Hey everybody. Welcome to another episode of Ruminate This with Agrarian Solutions. I am your host, Scott Zehr once again, and also again joined by Dr. Larry Roth, our Vice President of Nutrition here at Agrarian Solutions.
Over the past couple of months here in 2026, we have spent time doing more of a deep dive into, Larry I’m gonna say the big four mycotoxins that we see in the US. Don, also known as vomitoxin, zearalenone, T-2, HT2, and fumonisin. And so Larry, I want to thank you one ’cause I felt like those episodes even for me were very informative.
So hopefully the listener got something great out of those episodes and learned a little more about what these mycotoxins do on a biological level. Larry, we get to see sample reports, you and I do, and other team members here at Agrarian from across the country daily, almost. Thousands of samples a year.
And Larry, I tell you what, it’s getting less and less common to see one mycotoxin show up on a sample. Just certain growing conditions, I’m gonna say. Weather patterns, whatever it is. This past week or in the past two weeks, I should say, going back to the beginning of February, 2026.
The first 13 days in February of samples that came in, in my region of the US, not a single sample came back with less than two toxins. Many of them had four. All four that we’ve discussed. One particular sample assay that comes back to mind was in the closeup pen of a dairy, so the closeup TMR sample.
Dr. Larry Roth: Mm-hmm.
Scott Zehr: High zearalenone, high DON, T-2, fumonisin. I’ve asked you this question before, Larry, but I’d like you to just kind of reiterate or frame it up for us to understand better. But, what happens biologically to that cow when she’s exposed to all four of these mycotoxins simultaneously?
Dr. Larry Roth: Wow. That’s a great question, Scott. What happens when that cow is challenged by all four of our more common mycotoxins? Well, there is a, rather than being additive, Scott, the effects coming together think of it as being more multiplying each other. Because each particular mycotoxin strips away a layer of protection. So they just gotta think of it as multiplying each other.
Scott Zehr: Yeah.
Dr. Larry Roth: Where destroying digestive tract integrity, so it’s easier for more of the other mycotoxins to get into the blood system. Then we’re slowly destroying the liver. We’re changing hormone balance. We’re taking down the immune system. And so each mycotoxin has, shall we say, a multiplying effect on the others. And that that’s what makes this kind of interesting is we can’t say it’s just a certain level of each one that causes issues, because when we have multiple mycotoxins, the threshold level for the cow to defend herself is reduced more and more by each mycotoxin that comes into play.
Scott Zehr: No. When you say it like that, I think of a term that’s used in business, especially marketing called beachheading.
Dr. Larry Roth: Mm-hmm.
Scott Zehr: So beachheading referring to when we put all of our troops on the beach in Normandy to storm the front and concentrated everything in one area. Well, you know, if we had just one mycotoxin in the TMR for instance
Dr. Larry Roth: mm-hmm.
Scott Zehr: So, you know, when, if we just had one mycotoxin show up in the diet, it honestly, it’s almost like a win. Because if DON’s going in there doing bad stuff in the rumen causing some inflammation, the immune system’s gonna send all of its effort to that area, right? Or to take care of that thing. But now, you have four different mycotoxins each with a different attack mode or attack protocol.
Dr. Larry Roth: Yep.
Scott Zehr: And you know, so that immune system’s gotta go in many different directions. Is that kind of how that would work?
Dr. Larry Roth: You bet. Yeah. Now we got four different mycotoxins that are attacking the immune system or the liver. I’m gonna back up to, and I really like your analogy, the beachhead use of that term.
Think of the beachhead here as breaking through the castle wall. That’s the dog. We’re disrupting the rumen lining, we’re disrupting the small intestine lining, so it’s that much easier for everybody to get into the body. And now the immune system has to deal with multiple mycotoxins. Now the liver has to deal with multiple mycotoxins.
So yeah, I kind of like that beachhead term. We just have to get that break in the digestive track lining, and then everybody comes ashore, if you will, and gets into the animal to cause their mischief.
Scott Zehr: Yeah. And, and I think, we’ve talked in the past about this and it feels like oftentimes it becomes a, almost like a chicken in the egg conversation. What’s worse? One mycotoxin at a really high level? Or three or four mycotoxins, even just two mycotoxins at a lower to moderate contamination risk? I’ll let you expand on that.
Dr. Larry Roth: I’m gonna go ahead and vote for the multiple.
Scott Zehr: Yeah.
Dr. Larry Roth: ‘Cause again, each particular type of mycotoxin strips away a certain level of protection.
Scott Zehr: Yeah.
Dr. Larry Roth: So I really do like thinking of the effects being multiplied rather than being additive. So I would vote for multiple mycotoxins at lower levels as being worse than a single mycotoxin at a higher level.
Scott Zehr: Yeah, I think that makes a lot of sense. It just each one that’s there, they just attack a different way, so it creates more problems. Yep. So, I wanna think about some of these assays that I’ve seen come through, and I’ll just kind of do a back and forth with you. What do we need to be concerned about when we see DON with fumonisin?
Dr. Larry Roth: Okay, DON and fumonisin. Well, the DON is breaking through the castle wall, increasing gut permeability, and then you got fumonisin that has a liver effect as well as taking down the immune system. So we’ve got gut permeability and inflammation taking place.
Scott Zehr: Okay. How about fumonisin with zearalenone?
Dr. Larry Roth: Okay. Similarly, we got fumonisin taken down the immune system attacking the liver, and then we’ve got zearalenone disrupting hormones.
Scott Zehr: Okay. How about DON and T-2 running together?
Dr. Larry Roth: Okay. DON again, come back to our gut permeability is increased and this can be rumen or small intestine. And then T-2 just takes everything down. That’s the finisher. When we talked about T-2 recently, we were emphasizing HBS, hemorrhagic bowel syndrome. So, we have increased gut permeability so that more bad guys get in and now we’re taking everything down to increase the HBS risk.
Scott Zehr: Yeah. And then I’m gonna throw this one at you, zearalenone with almost anything else that we, that we test for. ‘Cause there’s I think, a unique thing about zearalenone being fat soluble that plays into this.
Dr. Larry Roth: Right, right. Yeah. Well, again, zearalenone disrupts hormone balances and all of the others, they work either increasing gut permeability, taking down the liver and its detoxifying abilities. Taking down the immune system related to trying to reduce inflammation.
So think of zearalenone and anything else as we’re disrupting hormone balance and making it that much harder to protect the body and resolve the different issues. The key is that multiplying effect of multiple mycotoxins showing up in the feed.
Scott Zehr: Yeah. You know, and I think some things that, you know we see, I always say, okay, well what do I need to look for? Right? And so I’m, I’m thinking of inconsistent intakes with the, with the DON, right? Or, or erratic manure.
Dr. Larry Roth: Mm-hmm.
Scott Zehr: What, what are some other things we should probably think about?
Dr. Larry Roth: Okay. Milk production. Cows aren’t increasing in milk production like they should, being flat to trending down, and then the reproductive success. Cows aren’t getting pregnant and staying pregnant. Either because zearalenone is messing up the hormone balance or all of the other mycotoxins were showing up and causing inflammation issues that redirects nutrients to less profitable purposes, just trying to stay alive.
Scott Zehr: You know, one of the, I think things that we hear on a regular basis and I certainly experienced it when I was on the dairy. Why do I just all of a sudden have random cows going off feed? What’s causing this? And then you get the vet there and they’re like, “I don’t know.” Probably ought to look maybe towards the mycotoxins as being causative.
Dr. Larry Roth: Absolutely. Again, the analogy I like to use Scott is if we were to go to a real nice buffet, and if one of us wasn’t feeling well, that person’s probably only going to go up once or twice. Whereas if that person was healthy, man, they’d be going up time, after time, after time.
So when cows don’t like to eat, it’s probably because they’re not feeling well. And all of these mycotoxins can contribute to the cow feeling outta sorts, not eating like she should. And if the cow is eating less than what she should, we have fewer nutrients going in to take care of the immune system. The body’s military.
We have the cow not feeling well, not drinking like it ought to. It’s more likely dehydrated, and we lose our tight junctions. Tight junctions now become interstate highways for pathogens and other bad stuff in the digestive tract to get into the body. So again, I keep coming back to, with multiple mycotoxins, the effects aren’t additive. It’s more of a multiplying effect.
Scott Zehr: Yeah. You know, I wanna just kind of think about some takeaways here and we’ve all heard the term Dirty Feed before. And when I hear the term dirty feed, usually it’s, you know, it’s, it’s, it’s related to either high mycotoxins or it’s moldy or whatever. And, you know, we talk an awful lot of at Agrarian about feed hygiene.
Dr. Larry Roth: Mm-hmm.
Scott Zehr: And certainly I think mycotoxins fall into the conversation of feed hygiene.
Dr. Larry Roth: Mm-hmm.
Scott Zehr: But Larry, expand on this point, if you would. I don’t necessarily look, at this point in my career, to mycotoxins as being a feed defect or a feed hygiene issue, per se. But maybe I’m starting to think of it more as a challenge to the biological system that the cow is. Your thoughts on that.
Dr. Larry Roth: Yeah. I really like that biological system. We can back up all the way to the soil. Soil’s biological system. The plant’s biological system, the fermentation process is biological.
And then the feed being utilized by the cow is a biological system. And the cow itself is biological system. So you can see where, if we start to have issues with soil health relates to plant health relates to mycotoxin occurrence. So it’s also interrelated. And again, forgive me for repeating myself, Scott, it’s not additive. It has a multiplying effect.
Scott Zehr: Yeah. So, you know, let’s think about maybe Larry I’m gonna say traditionally the way that perhaps we have always thought to mitigate the effects of mycotoxins in cattle, right?
Dr. Larry Roth: Mm-hmm.
Scott Zehr: We had clay-based products or yeast cell wall fracture based products.
Dr. Larry Roth: Okay.
Scott Zehr: And, you know, they’re going back to the Cajal et al in 2022 research that we’ve discussed on this platform. There’s some binding that takes place on certain mycotoxins zearalenone as one of those ones that for instance is bound at a higher percentage than say DON is, but it’s still not a very high percentage.
Dr. Larry Roth: Right.
Scott Zehr: But I guess the way I wanna frame this question up to you is, if I have multiple mycotoxins present and I were to feed an ingredient that helps mitigate one of those, how much benefit is that going to give me?
Dr. Larry Roth: Okay, great question. Well, I think the classic research on this area, Cajal, et al from the December of 22 journal of Animal Science would suggest that yeah, there are variations between the different mycotoxin mitigation products for their ability to tie up mycotoxins, just as there’s variations in ability to tie up nutrients.
So tell me the mycotoxins in question. Tell me about the different challenges that the animal is going through and how the people are trying to manage the animal. And we come back to our biological systems. They’re all interrelated.
Scott Zehr: Yeah.
Dr. Larry Roth: That all starts with the soil.
Scott Zehr: So, I’m gonna ask you one more question here. And so, if we’re dealing with a biological system…
Dr. Larry Roth: mm-hmm.
Scott Zehr: And we’re trying to mitigate the effects of mycotoxins within a biological system, how does DTX play into that as a biological approach?
Dr. Larry Roth: Okay.
Scott Zehr: And what is DTX doing biologically to help that cow?
Dr. Larry Roth: Okay. What’s the logic behind using DTX? Well, we theorize that DTX being a live bacteria is working at the small intestine level because of small size to take up residence in some of the intestinal cells. Doesn’t have to be every cell because there’s something called quorum sensing where the cells kind of communicate across each other saying, “Hey, we’ve got something here. We need to elevate our ability to kick these mycotoxins out,” just like other waste products or undesirable substances, we have these export proteins. And the export proteins seem to be activated by the mere presence of the cell wall deficient bacteria.
So mycotoxin gets in, transport of proteins finds them, seeks to kick the toxin or undesirable substance back out into the digestive tract to flush down the river. And again, we don’t have to be in every single intestinal cell because there’s communication that takes place across the intestinal cells. So it’s really, it’s a neat biological system. The different animals, in our particular case, the one of greatest interest is the dairy cow. The high production dairy cow has that ability to recognize these pathogens and decide to kick them out. So it’s, it is really neat, Scott, how all of this is integrated together.
Scott Zehr: It is. And, I think that’s the, the unique approach here, right? Is, is that we’re not treating the feed, we’re not treating the mycotoxin. We’re elevating the cow’s ability…
Dr. Larry Roth: mm-hmm.
Scott Zehr: To protect herself by helping the rumen, the gut, the liver, the immune system, and the endocrine system.
Dr. Larry Roth: That’s right. Yep. And it all comes together. It’s also Integrated as that biological system.
Scott Zehr: Yep. Well, I, I really appreciate you doing these deep dives with me and in particular today’s episode because we, we do continue to see a lot of multiple mycotoxins, and I think sometimes we get hyperfocused on DON, or we get hyperfocused on zearalenone, and then if T-2 and fumonisin show up that, I’m gonna call it low contamination levels.
Dr. Larry Roth: Right.
Scott Zehr: We just kind of say, oh, well those numbers look low on the, on the assay, so we don’t really have to worry about it.
Dr. Larry Roth: Well come back to our multiplying effect. Each particular type of mycotoxin takes away one particular layer of protection. So again, that multiplying effect.
Scott Zehr: Yep. Awesome. Well, thank you again Dr. Roth for jumping on with us today and bringing this series if you would home and if you all have any questions you wanna ask of us, you can always go to agrariansolutions.com and fill out the question form on the website.
You can also email us directly, [email protected] and we can put you in touch with Dr. Roth or Caroline. We can make sure we answer any questions you might have in this space. My last takeaway, Larry, and I’ll ask you for one as well. I’m gonna say sample, sample sample. Test your forages regularly. Test that TMR on a monthly basis. Know what is going into that cow.
Dr. Larry Roth: Absolutely. And Scott, I would just encourage people to sample their different feeds going into storage.
Scott Zehr: Yes.
Scott Zehr: And then do the regular testing as we feed them out.
Scott Zehr: Absolutely. Alright, well, hey everybody, we’ll be talking to you again in a couple of weeks. Again, remember we air on the second and fourth Monday of every month. Have a great time.
Dr. Larry Roth: All right. Thanks Scott.
