In this episode, Dr. Larry Roth explains why zearalenone is fat-soluble, how it can be stored and released during post-calving fat mobilization, and why its metabolites may be even more damaging than the parent toxin.
Learn how it contributes to cystic ovaries, early embryonic loss, cows showing heat signs while pregnant, and inconsistent reproduction, as well as why some traditional binders can make things worse.
If pregnancy rates aren’t matching expectations, this episode shows why zearalenone could be the hidden disruptor and how targeted protection like DTX helps prevent absorption before damage occurs.
🎧 Listen now to set your herd up for lifelong success!
Scott Zehr: Hey, welcome everybody to another episode of Ruminate This With Agrarian Solutions. If you’ve been listening along, you know that my name is Scott, and if you haven’t, this is your first episode, I’ll say welcome to the podcast. I’m glad you’re tuning in. Make sure you hit that subscribe button, and if you find value in any of our episodes, share them with a friend. And see if we can spread that value.
So today we’re gonna be visiting with Dr. Larry Roth, vice President of Nutrition here at Agrarian Solutions. And we’re gonna dive in, do a deep dive similar to like we did with the mycotoxin DON. Only today, Larry, I’m gonna ask you to deep dive with me about zearalenone. Specifically, I think there’s a lot of things that we know about zearalenone in the industry.
Dr. Larry Roth: Yep.
Scott Zehr: I think it’s pretty standard parlance to be having a conversation about zearalenone, and people will say things like, it’s the estrogen imposter or mimics estrogen, or the cows recognize it as estrogen. And inherently, we know that if there’s hormonal issues caused by, by zearalenone, what’s the first thing we go to to look at? Reproductive success.
Dr. Larry Roth: Yep.
Scott Zehr: But, you know, zearalenone is doing a lot more than just mimicking estrogen. So I guess where I’d like to start with you, Dr. Roth, is we know it can mimic estrogen, but what are some other things that it is doing that we don’t always think about?
Dr. Larry Roth: You bet. So yeah, as you said, we think of zearalenone being an estrogen imposter, getting bound at those sites. But zearalenone also interferes with general hormonal balance in the cow. And so we see hormones aren’t working as they should be. The cow is a well-oiled machine when it comes to hormonal sequences, so that she’s ovulated at the right time. She’s ready to get pregnant at the right time. But all of that gets messed up when we’ve got zearalenone issues.
Zearalenone also has an impact on the liver, in that zearalenone and its metabolites are more like a poison to the liver. And so it interferes with liver functioning as the body’s biochemical factory. So there’s really a neat story behind zearalenone, not just reproduction, but it also impacts the immune system as well, and to a degree, the digestive tract.
Scott Zehr: Okay, so, before we get into the liver and the digestive tract. Quick review and take a look at the domino effect from the reproductive side, the side that everybody always thinks about. What is, what is the domino effect there? How is it impacting reproductive success on our dairy farms?
Dr. Larry Roth: You bet. Well, first of all, again, zearalenone functions in many ways as an estrogenic imposter. Takes up residence on the estrogen binding sites. And so from that we are disrupting follicle development, follicle release. Also have an impact upon the uterine environment in that the uterine wall becomes thicker, and it’s harder to get the embryo to implant so that it can develop. So we’ll see some early embryonic death.
Zearalenone is interfering from a hormonal standpoint with so many different hormones throughout the body. And it’s also regulated, closely regulated in, in terms of how it works. And so little upsets here and there tend to magnify their impact.
Scott Zehr: Yeah, so there’s quite a synergistic effect there, or domino effect, if you would, where if we’re disrupting the hormonal cues, right, that’s needed for ovulation. I mean, you’re talking about follicular development, you mentioned decreased follicle quality, the uterine environment, and early embryonic death.
To me, that one is one that I think back through my career, Larry, spending time in the genetics world and, and breeding cows. And we always seem to, huh, this is funny because it’s, it’s like I had a story about this here recently that played out on farm. But as an industry, we kept moving, right?
Technology increased. So we went from palpating at 40 days and above to really good veterinarians with really good field getting down to 32 days. And then ultrasound, getting down to 28 days, and bloods getting, you know, a little bit further there. And we saw early embryonic death increase the more we lowered the threshold for pregnancy awareness.
Well, that makes sense. The highest risk of early embryonic death happens in that, what, 20-28 to 35 day window? Give or take a day or two folks. Don’t quote me on that. But, early embryonic death became one of those numbers as a technician that I really, really looked at, and what can we do to improve it?
Well, I was always told that it’s just a byproduct. The, the only reason that number is getting higher is ’cause we’re preg checking sooner. Larry palpation success rate is one of those quiet little KPIs that I think, I almost call it the feel good KPI. If we have a good herd check today, Larry, we feel good. You know, if we have 18 out of 20 pregnant, we feel good. If we have 10 out of 20 pregnant, we say, oh, it was a bad week. We’ll hope for a better, a better outcome next week.
The palpation preg rate is also one of the things that I advise farmers to look at as an early indicator of the success of DTX, especially when there’s zearalenone involved. Because we see over and over again, all of a sudden there’s more cows pregnant on Vet Check day. And I’m gonna say, I’m gonna infer that we are helping reduce that early embryonic death loss because of zearalenone. Now can I prove that? No, this is observational, my observational stuff that I see in the field. So Larry feel free to comment on that.
Dr. Larry Roth: Okay. So, yeah. The zearalenone is interfering with corpus Lium, with progesterone production, which we think of being the hormone that promotes pregnancy. I also come back to zearalenone has impacts on the immune system. We think so often zearalenone is a direct reproductive villain, but also it, it, it changes what’s happening with the immune system.
So if we activate the immune system, we gotta have glucose to fuel the immune system. We don’t have glucose to donate carbons to rapidly growing cells. And I think that also contributes to early embryonic death. So zearalenone yes, it, it works in terms of blocking estrogen binding sites. But it also impacts a whole lot of other parts of the body.
Scott Zehr: Yeah, very good point. So you mentioned the immune system, and I’m going to actually ask you to dive further into we’re, we’re gonna come back to the immune system part of it. But I want you to dive further into the, the liver.
So, you know, you love talking about that biochemical factory, Larry. I know you do. So, walk us through what’s happening to zearalenone once it gets to the liver and, maybe what the liver has to deal with when it’s, when it’s trying to treat zearalenone, I guess.
Dr. Larry Roth: Okay.
Scott Zehr: Or detoxify zearalenone.
Dr. Larry Roth: Without getting into all of the physiology and the enzymes and so forth working in the liver, it seems that the liver looks at zearalenone as more of a hormone than a toxin to be detoxified and broken down. So consequently, the liver is not, is able to break down DON. Is it is able to deal with LPS, the lipo polysaccharide, and also able to handle the deepa.
So we think of what’s going on with the cow in the first part of her lactation. She’s going through tremendous energy demands. Fat is being broken down. We have NEPAs that are being created that need to be handled by the liver. But they’re not getting handled by the liver because the liver unfortunately is getting tied up with zearalenone, which is being recognized as a hormone and not as the toxin that it is.
So consequently, the liver isn’t able to get rid of all of these oxidative species, the canon balls that we talked about during our DON discussion. And we see that inflammation will gradually creep up throughout the body. So we see things like mastitis, metritis that gradually start to build up. The liver and the immune system just is not able to deal with all of these metabolites that get created.
So zearalenone isn’t just directly impacting repro. It’s impacting repro in many different ways. And some of that has to do with the liver as well as the immune system. And interestingly, we’re starting to understand now that zearalenone impacts the rumen. You know, normally we didn’t think of that if we’re talking about…
Scott Zehr: Right.
Dr. Larry Roth: what mycotoxin affects the digestive tract, well, that would be DON. but it seems that high zearalenone levels slows rumen turnover. So the animal isn’t able to consume as much feed, as many nutrients. We, we just need rumen turnover to happen so that some of these nutrients are now being presented to the small intestine instead of being broken down too far. Things like the amino acids. So we’ll see variations in manure, and some of that may be due to zearalenone.
So that, that’s where we keep coming back to how these mycotoxins are also interrelated because they may be affecting the same part of the body, but coming about it different ways. So interesting that zearalenone has a dramatic impact upon the rumen, our fermentation factory that drives the animal.
Scott Zehr: That, that is interesting. And you know, we’ve talked before about the synergistic effect of multiple mycotoxins present in the TMR and, DON is, almost like an indicator toxin in a way.
Dr. Larry Roth: Yep. Yep.
Scott Zehr: But you know, if you look through our, our archive of samples, very common to see zearalenone and DON together, like they, they like to run in the same circles.
Dr. Larry Roth: Yep.
Scott Zehr: So, you know, when you think about the direct influences that DON is having on the rumen and then the direct influences that the zearalenone is having on the liver, boy it stands to reason when you pair these two together. And I’m gonna go back and say it Larry, like we saw in the study we did on DTX, where we had 1.5 PPM DON and 150 PPB zearalenone. Maybe that’s why we were able to see what I would call better utilization of nutrients and improved reproductive performance.
Dr. Larry Roth: Exactly. The mycotoxins are creating a problem from several different angles. And now here we are with DTX, able to work against both of the mycotoxins. So it just stands to reason that if multiple mycotoxins exacerbate the problem, DTX is gonna be that much more important to use in multiple mycotoxin situations.
Scott Zehr: Hmm. So, you know, we, we talk a lot about inflammation
Dr. Larry Roth: Yep.
Scott Zehr: I wanna ask you this question, Larry. And that is, if I’m a herd out there today, maybe struggling with some metabolic issues. Oh, what’s a good example? Maybe the percentage of cows with BHBA over 1.2 is, is starting to creep up there. Maybe we’re not seeing clinical ketosis, but certainly we have signs of increased subclinical ketosis. Or potentially even milk fevers creeping up or metritis creeping up.
And you’ve, you know, you’ve had the conversation with your nutritionist. We talked about it with the vet. We’ve made some changes to the diet, but something still isn’t quite clicking. Why should I take a look at zearalenone going into my cows as a reason or as something that could be causing some of these metabolic issues?
Dr. Larry Roth: Well, just, just like what we’ve been talking about, zearalenone affects the body more than just plain estrogen levels. It is affecting energetics of the animal, how nutrients are partitioned affecting rumen function. So many different things are coming into play. So we, we think about glucose metabolism being so important. We’re talking about glucose being the fuel for the immune system, donating carbons to rapidly growing cells.
I like to say no glucose, no lactose, no milk. Well, if zearalenone is impacting the immune system, we have all these oxidative cells, oxidative species bouncing around the body, and liver isn’t able to clear those because the liver is all tied up with zearalenone. You can just see how so many different things come into play, all coming back to zearalenone. So we think, okay, zearalenone, that’s just the repro mycotoxin. No. Zearalenone impacts really the entire body.
Scott Zehr: So I’m glad you framed it up that way. Zearalenone is the repro toxin. Because when you look at the, I’m gonna back up. When you look at the domino effect of DON, ultimately, what is it effect? Repro.
When you start cascading, I think the, the analogy we used on DON was, was floating down the river bank or floating down the river and you end up somewhere and where do you end up? You end up trying to get that cow pregnant when she’s having to allocate nutrients to repair cells inside her body.
Dr. Larry Roth: Yeah.
Scott Zehr: And then when you put zearalenone, which is, I think I would call it maybe a direct influencer of poor reproductive success. Makes a lot of sense. But what’s coming out here is that it’s also maybe an indirect influencer of poor rumen health. And I think that’s an important one to remind people of that.
If, if just because we have low levels of DON doesn’t mean we’re having, and, and there’s zearalenone present, doesn’t mean we’re having less rumen issues per se, because the zearalenone could be helping the DON out there too.
Dr. Larry Roth: Absolutely. Yep. I think another thing we wanna talk about is if zearalenone is absorbed into the body, it does go through some metabolites, metabolism, excuse me. And some of these zearalenone metabolites are actually harder on the cow than zearalenone itself. And there was a…
Scott Zehr: Oh wow.
Dr. Larry Roth: Clay product that has some research done and presented at American Dairy Science Association in 2024. And what was shown was that when this clay was fed there were higher levels of zearalenone metabolites that when the clay was not fed, which on its face is very interesting.
And so the zearalenone metabolites were a worse issue, more negatively impacting the animal when they, when this clay was being fed. So we gotta think about how are we gonna protect the cow against zearalenone and it isn’t feeding these different binders because this research study suggested that we had higher levels of these zearalenone metabolites. That’s where we need to bring in DTX, keep the zearalenone from being absorbed and going through the metabolism and all of the other inflammation that we’ve been talking about for many different sessions.
Scott Zehr: Yeah.
Dr. Larry Roth: So let, let’s just think about, keep zearalenone out of the body. Because it’s gonna impact the cow in so many ways. I think so often we forget about the important roles of hormones and the endocrine system, how it affects metabolism in so many ways.
Be it, glucose dynamics, amino acid and protein metabolism, and the zearalenone comes in and just alters so many of these different hormones, and that’s where these cows just get kind of off. We, we can’t say, well, man this is a real problem right here. It’s more the cows are kind of blah. They’re just kind of off.
There isn’t a snap to them. Well, that’s because the hormones, the endocrine system is off, because of zearalenone. So think of zearalenone is being kind of a sneaky little mycotoxin that alters so much of the cow besides just the repro system. And then we, we can think of perhaps the cow is being kind of a pyramid and at the top of the pyramid is reproduction.
If, if the base of our pyramid is off, everything above that is gonna be affected. And the reproductive, reproductive success is kind of the pinnacle indicating that the cow was working right.
Scott Zehr: Yeah.
Dr. Larry Roth: So zearalenone…
Scott Zehr: That’s a great point.
Dr. Larry Roth: Impacts each layer of our pyramid, not just the reproduction.
Scott Zehr: So, when I talk with people in the field about the different mycotoxins that we see, and, and I’m speaking specifically to the Eastern, Eastern US here and, and, you know, we see, we see DON and, we will have a conversation about DON, what it’s doing, what it’s not doing. We’ll have a conversation about fumonisin, especially over the last year and a half.
We occasionally have conversations about T2, HT2. And as well as zearalenone. But Larry zearalenone is the only one that ever becomes controversial in the sense that when I, when I say things about zearalenone, I’ll have a response like, oh, that’s a myth. That’s not true.
And what they’re referring to is zearalenone’s ability to work its way inside those fatty tissue cells and be stored in the body. And basically just lie and wait for an opportune time to wreak havoc on the liver.
Dr. Larry Roth: There you go. Yep.
Scott Zehr: So is it a myth, Larry? Or what’s going on there with zearalenone and being stored in the body?
Dr. Larry Roth: I think this is an important part to bring up. Zearalenone is fat soluble. So it can be picked up as the cow picks up body condition, or even the heifer. And zearalenone is stored in the fat and its metabolites also. And it’s just laying there waiting until the fat is broken down. So the cow freshens, she’s in negative energy balance.
She’s gotta break down her fat reserves for energy. And zearalenone is now released to be floating around the body and causing its mischief. So that is where zearalenone levels during the dry period or even the late lactation period are extremely critical. So the issues that we’re seeing today with the newly transitioned cow, the cow that we’re trying to get bred and she isn’t breeding back.
We need to be backing up and saying what was going on during the dry period or even during late lactation. Because if we had higher zearalenone levels during late lactation and dry period, she was storing up fat reserves and also storing up zearalenone. Now that she’s breaking down her fat reserves, zearalenone is being released to go throughout the body and cause all of its mischief. Hmm.
Scott Zehr: Okay, well there we go. We have that myth Busted. Larry. It does happen folks. And you know, I, so I go back to that ketosis question that I asked you or the metabolic question. And you just think, and we’ve, we’ve discussed this before. But we think of all the things that we ask that cow to do the day she calves. That liver is busier than ever.
Dr. Larry Roth: Yep.
Scott Zehr: There’s all kinds of inflammation. And now you’re gonna ask it to also detoxify the zearalenone that is being mobilized from the, the energy reserves. Like you always say, Larry, what could go wrong?
Dr. Larry Roth: Absolutely. You got it.
Scott Zehr: What could go wrong? So, before we wrap up, Larry, I just want to ask and maybe we can go back and forth on this, but some things to look for within your herd to help diagnose whether or not we maybe are experiencing challenges from zearalenone.
And Larry, I’m gonna start, I’m gonna start off by one that we don’t see a lot. But I have seen it in the field, and we tested the forages. We found high levels of zearalenone, swollen mammary glands in heifers.
Dr. Larry Roth: Yep. There you go. Yep. Again, zearalenone and its metabolites interfere with mammary cell development. Where you were going, where I thought you were going with that, Scott, was cystic ovaries. Something that we haven’t, that’s what mentioned.
Scott Zehr: I think everybody was thinking I was gonna go there, but I wanted to bring that one, bring that one off the bench. ‘Cause it’s, it’s one of those ones you don’t see a lot. ‘Cause we don’t really feed a ton of corn silage to heifers. But, you, you see it from time to time and, and it’s always chalked up as well. That’s weird.
Dr. Larry Roth: Yeah. Right there. I think if you see more weird things happening, it’s more of an indication that we got zearalenone issues, because it’s such a sneaky mycotoxins.
Cows are just kind of blah, they’re not really snapping into lactation, mammary glands aren’t developing as they should or, or maybe they are developing too early. When things are just off. We don’t consistently have a loose manure. Some days it’s loose, other days it’s normal. There’s just a lot of variation.
All of that is pointing toward issues with, with zearalenone. You know, we, we get into a batch of cows where maybe we have a little bit higher incidents of ketosis or, again, cows just aren’t getting bred well, that backs up to pointing toward zearalenone and how it was interfering with the liver and glucose metabolism.
So zearalenone sometimes it takes a backseat to DON. But, zearalenone is, again, it’s kind of that sneaky mycotoxin that affects so many different parts of the cow’s body. In those low, little low level ways that all put together magnify the issues that they’re causing to the cow.
Scott Zehr: Yeah. Yep. You mentioned the cystic ovaries. We talked about higher than normal early embryonic death. You know, some other indicators that you’ll see in the field. One of my favorites is if you have pregnant cows that are showing signs of being in heat. Okay, so what do we do, Larry? We put ’em on the vet checklist and the vet goes and, and runs their arm up or checks ’em again.
Why is this cow on the vet checklist? She’s still pregnant. Well, she was in a standing heat last week, so that’s why I put her on the list.
Dr. Larry Roth: Yeah.
Scott Zehr: You know, if you’re seeing that more often than not, you, you may wanna consider zearalenone. Any other couple things you wanna leave with the audience before we head out Larry?
Dr. Larry Roth: So, simple little message. If things just seem out of whack, aren’t making sense, we probably need to look at zearalenone.
Scott Zehr: That’s a good one. And actually Larry, that is a callback. Look at you, old podcast pro. And so I’m going to send you guys back to an old saying that I have and we did an episode on this and I think it was called When two + two Equals Five.
So that, ironically enough, is episode number five, when two plus two equals five. And you know, Larry, I have this theory that when two plus two no longer equals four, it’s probably mycotoxins. And so in that episode, I believe Jeff hosted and I discuss that. And we talk about just what you said. When things seem weird, when things seem off. We can’t really put our finger on it, look to mycotoxins.
Dr. Larry Roth: There you go.
Scott Zehr: And, and zearalenone. So thanks for that call back, Larry. I appreciate it. And I appreciate you once again taking time out of your day today. And we’ll be talking to the audience again in a couple of weeks. Thank you, Larry.
Dr. Larry Roth: Right, thanks Scott.
