Mycotoxins like DON, zearalenone, and fumonisin silently drain herd health and profits, but too often, testing only happens after the damage is done.
In this episode of Ruminate This, Scott Zehr and Dr. Larry Roth discuss why routine, proactive mycotoxin testing of TMR and silage should be a standard practice on every dairy. They explor regional mycotoxin trends, the influence of agronomic practices, and the role of residue management. Learn why monthly TMR testing, especially in dry cow and pre-fresh rations, is the most reliable way to safeguard milk production and herd health.
Take control before losses occur. Download your complimentary Mycotoxin Report from Agrarian Solutions at agrariansolutions.com/mycotoxin-report-april-september-2025 and see the latest trends impacting herds. With proactive testing and resources like this, protecting herd health and profitability has never been easier.
🎧 Listen now to set your herd up for lifelong success!
Scott Zehr
Hey, welcome everybody to another edition of Ruminate This with Agrarian Solutions. I am glad to be here. I am Scott, by the way, as you probably have figured that out. I am joined by my partner in crime, Dr. Larry Roth today.
And, we’re gonna be talking about toxin assay results in a sense. But really, Larry, I think what I’m hoping to accomplish today for the listener is the value in sampling and understanding the samples. You know, you’ve had a chance to review data from the last six months, right?
Dr. Larry Roth
Yes.
Scott Zehr
But at the end of the day, why did, like none of the numbers in the assay results actually matter unless it matters to me on my farm. Right.
So yeah, I think there’s, there’s a lot of value and the data collection that we do with toxin results, and we’re gonna dive into that. But I want you as a listener to be thinking to yourself, okay. You know, why is this concerning me? And hopefully we can answer that question today.
Dr. Larry Roth
Mm-hmm.
Scott Zehr
Dr. Roth. A, thanks for jumping on with me again today. B, we’ll start in your home area region and dive into some of the Midwestern states there and what are you seeing for trend levels on our big five mycotoxins.
Dr. Larry Roth
Okay. Hey Scott. I’m glad to join you here today. The big five, well, one of ’em is suspicious by its absence. Once again, we did not come up with any aflatoxin being found in corn silage, no surprise there. But also did not find aflatoxin in the TMR. Generally, where we’re gonna see aflatoxin showing up is if we’re feeding some cotton byproducts or peanut byproducts.
Otherwise, by and large, thanks to our corn geneticists with virtually eliminated aflatoxin from showing up in these diets. But I think that what’s more interesting is to look at the trends. And, DON continues to be an issue. We think about two things. Weather that challenges the molds and they say, Hey, I gotta do something to preserve my dominance of this neighborhood I live in.
So I’m going to create a poison that kills all the other microorganisms trying to take off my spot. A fusarium mold, Scott could care less about some Holstein cow someplace that is gonna consume itself. The fusarium mold is concerned about other microorganisms trying to take away its home.
So we look at what’s happening in the upper Midwest and we’re starting to see DON show up in greater levels, and part of that is due to weather. But part of it, I think, is due to what’s happening in the soil. If we start to have the fusarium molds show up and we are doing good agronomic practices, lots of organic matter, lots of surface residue, so we don’t get erosion, that’s a natural reservoir for the fusarium to build up in numbers over time.
So good agronomic practices, ironically, could favor more of the molds being present. But just having the mold present doesn’t mean that we have a mycotoxin issue. You gotta have that stress. So there’s some states with very nice, even weather where we don’t see mycotoxins showing up. Other states that maybe they have too wet weather or too dry.
Too much of anything tips the balance over toward these mycotoxins. So DON and zearalenone seem to be issues, but again, who cares? I’m concerned about at my farm.
Scott Zehr
So exactly right. And I wanna go back to your last statement here, real quick. Question that popped into my head. You talked about the agronomic practices, right? And essentially trash in the field. My time spent in Minnesota and Iowa was very limited, but I saw something out there that I do not see happen in New York.
Dr. Larry Roth
Okay.
Scott Zehr
And that was after the corn was combined off. We brush hogged it, they wheel raked it, and they bailed it. And they use it for betting FOD or whatever. How valuable is that from helping to mitigate toxins on a field level?
Dr. Larry Roth
Okay. Wow. That’s a very interesting question and I’ll go back to a comment that you made and you referred to the residue as trash, and that’s how we often viewed it as trash is we gotta do something with it because it might not break down.
And we’re gonna come plant soybeans in this field if we’re doing a rotation next spring, and we don’t want that trash there to cause us problems. We would try to make a very nice seed bed for planting soybeans and more importantly, soybean emergence. So we try…
Scott Zehr
Well, that trash actually has value.
Dr. Larry Roth
Absolutely. Absolutely. So we would call it residue. Maybe we should term that, change that term to where it’s a resource. Personally, on my farm, I love to bed with corn stalks. And we could get dry corn stalks put up and cattle love to eat it. Now there might not be a lot of nutrition there, but at least they’re got something to chew on.
So, we have the equipment today where we can make good corn stock bales. 30 years ago, our bailers weren’t a quality to do that, right? So today we can remove some of the, shall we say, corn forage put it to use as bedding, certain diets. We can even grind those bales and it can help out a certain grower type diets.
So let’s think of it as a resource and how can we put that resource to use. Create some manure that we can put back on the field so we get the nutrients, we’re better able to get out there, get our groundwork. Get it warming up next spring for when we go to plant. And everybody wins.
So it’s integrating agronomics into what we’re trying to do from a livestock standpoint, create a very clean feed hygienically. And when I say that, I mean low end yeast and molds and low end mycotoxin. So this is where it gets kind of interesting, Scott. How do we integrate all of this together on the farm, the agronomics and the livestock production aspects?
Scott Zehr
Okay, so Larry I don’t want to get too far down a rabbit hole, but I think that’s something that you know, I think it maybe is more challenging to get that off here in the Northeast and get it put up right. That’s why we don’t see it.
Dr. Larry Roth
Yep.
Scott Zehr
But, I’m glad we talked about that because I do think that there’s certainly an impact in helping reduce toxin levels there. That’s my opinion. You could tell me if I’m right or wrong. But coming back to this idea that really, it doesn’t matter what the numbers are unless they’re relevant to my farm. Coming out east a little bit, are we seeing over the last six months a rise or decrease in any of the particular toxins? And if so, what are they? And then we can kind of dive in from there what the concerns might be.
Dr. Larry Roth
All right. Yes. And Scott, I think that’s where the survey comes into play.
Scott Zehr
Yeah.
Dr. Larry Roth
The survey doesn’t tell me what’s happening in my farm, but it tells me what’s happening around my farm.
Scott Zehr
Yeah.
Dr. Larry Roth
And we’re starting to see more fumonisin show up in a variety of different spots. And fumonisin, we think of is more of a warm or hot weather mycotoxin. DON, zearalenone is cool, wet. Fumonisin can be wet or warm or hot, dry. Fumonisin attacks the liver. And we’re seeing more fumonisin show up in a variety of spots.
Now what’s gonna be interesting is as we go forward and we see more of the 25 crop being assayed and fed, do we see more fumonisin? Here in the upper Midwest we had a warm, wet summer that ought to tip the balance toward fumonisin. We had a very warm fall, very warm corn silage season here in the upper Midwest, and I think we’re probably gonna see more fumonisin show up.
But again, the survey is trends, tells us what’s happening, but I need to be testing to see what’s happening on my actual farm. And, and so that, that’s where we integrate the survey in with what my practices are at my farm. What should I be doing?
Scott Zehr
Well, I’m gonna answer that question. You know, I, I recently listened to a podcast Larry and they were talking to a farmer. I’m not gonna share all the gory details, but essentially this farm was having some troubles. And the troubles went on for nine months. They included, you know, they brought in people from universities to do blood sampling on cows, to diagnose repo problems. We had, you know, veterinarians involved, nutritionists involved.
This is, you know, them telling the story. And as I listened to that, I was kind of wondering where this is going. Like, I wonder, ’cause you, you want to know what the end. You know, what was the big thing? Mm-hmm. Nine months into this issue, somebody decided to pull a toxin sample.
Dr. Larry Roth
Okay.
Scott Zehr
They did a sample. They discovered there was mycotoxins present, and they traced all that back to that. So, great. What’s the takeaway for me? For me, the takeaway is, Larry, why is it not standard operating procedure in 2025?
Day one, pull the toxin sample. We’re chopping corn this week. Pull some composite samples out of the bunk every day. Mix it all together. Store it in the fridge. You get all said and done. Send it off. We’ll test it for free. We’ll cover the cost. Here’s another thing, and I’m I, I’m gonna be a little bit hard on the industry professionals that are on farms.
But I, I hope they take it as a challenge. You know, you pull into a farm’s driveway and you, you want to get their business. So what’s the first thing you wanna do? Hey, we’re gonna sample your feeds and I’ll put together a diet. You’re pulling a sample before you ever work for this customer, but you’re not testing for mycotoxins? So, again, I don’t wanna, I don’t wanna step on toes, but…
Dr. Larry Roth
So you just think about what you said, Scott. I’m trying to get a dairy’s business, so I’m gonna sample their feeds because I know there’s variations in feed, nutrient values. Doesn’t it also fit with that, that there could be variances in mycotoxin levels? And I see that just as, as a good management practice.
Scott Zehr
Yeah.
Dr. Larry Roth
To know what’s happened from a feed hygiene standpoint.
Scott Zehr
Yeah.
Dr. Larry Roth
Should, should be routine for a troubleshooting standpoint? And if I’m testing frequency varies with, with size of the dairy and how many fields that they’re pulling corn silage from and how much they’re sampling or how much they’re feeding different byproducts.
But I should be doing this on a routine basis. I’m gonna go ahead and say on a monthly basis. That way I’m always staying top of what is happening so that if things start to go negative, I can look back real quick and say, ah, here’s what’s been happening with our feeds. From a mycotoxin standpoint, a nutrient standpoint, I can start to identify.
But think about that dairy that you were just describing. Nine months of trying to figure out what the issue is. And they finally stumbled upon mycotoxins. Scott, what if they had sampled the corn silage going into storage? They could have known right away what their nutrient profile was gonna be. They could have known what mycotoxin risks were gonna be and put together a management strategy from both a nutrient standpoint, a mycotoxin standpoint, and have avoided the nine months of reduced performance, reduced economics.
Scott Zehr
Well, it’s exactly right. And I mean, people just, know. I am not trying to be Mr. Scary guy here, but like we’re seeing DON, zearalenone and fumonisin in particular pretty much everywhere. You know, I mean it’s, the levels vary by region. But it’s pretty much everywhere. And you, you can’t wait to find out until the program’s already stuck in the ditch, right?
And I think one of the things that I, Larry, I, I think it’s sometimes hard to diagnose these things we’ve talked about that at length on this platform, because mycotoxins aren’t there waving a big old flag. Right. They just kinda whisper the problems to the cows. Mm-hmm. You know, repro starts to slide.
I call it, I think I had a conversation recently with a nutritionist and I just said, hey, are you seeing any sneaky transition problems creep up? Like it maybe doesn’t look like a big deal, but something is sneaking into the success of the transition program. You know, like you said, testing, going into storage.
How many guys over the years have hung out with a pair of shears and a wood chipper and wanting to know the, you know, what the nutrient value of that corn is and the moisture so we can know when to chop.
I mean, why do we, I guess, Larry, the question that I think I’m trying to figure out is why aren’t people more willing to be proactive when it comes to pulling a forage sample while we’re chopping?
Dr. Larry Roth
Yeah. I, I don’t know. I don’t know. It seems like we would want to prepare for these potential challenges in advance. Know what our inventory is going to be.
Scott Zehr
Yeah.
Dr. Larry Roth
I think we would wanna do that. And here at Agrarian we offer this as a free service.
Scott Zehr
Yeah.
Dr. Larry Roth
So, I would really encourage people to start making plans for the 2026 year. Man, I can’t believe we’re already talking about 2026.
Scott Zehr
Yeah.
Dr. Larry Roth
Corn silage, but start making plans in advance of what we’re going to be doing from a management standpoint. Testing for nutrients, testing for mycotoxins. It just lets us put together a whole feed ingredient. What do we need to go out and get contracts on? What do we need to be doing from a mycotoxin mitigation standpoint to prepare for these events that are coming up?
Scott Zehr
The answer to the question that I asked you, and I don’t know the right answer, right? But probably, maybe, they just don’t test because it’s not built into the choppers, forage lab, harvest lab, you know, programs and stuff like that. Which is actually a fun idea. You know, maybe somebody in that world can just put a, put a needle on a dial and when they’re driving through the field harvesting and it turns red, they, it might alert them to actually test.
Dr. Larry Roth
Yeah. Because we’re, we’re monitoring for yield, we’re monitoring for moisture.
Scott Zehr
Yeah.
Dr. Larry Roth
So yeah, that’d be interesting concept.
Scott Zehr
You know, I think as we kind of flesh this out a little bit, you know, again, I’m challenging people like please start making this a day one SOP. As Larry just said, you know, we’ll cover the cost of the sampling. And I’ve, I’ve even made the you know given people the option, like, especially if you’re on the east, eastern side of the US where I work, but I’m sure Chad would be happy to do this as well in the Midwest.
Let us know when you’re gonna start chopping. Like, we’ll come down and help pull those samples. It’s something that we, we will help you do. Larry, let’s talk about the apprehension of sampling, maybe from the nutritionist side of things. There’s times over the last four or five years that I’ve been here at Agrarian and even in my previous life, going back to when I was on the farm at home. It seems like there’s, we’re apprehensive to test, number one.
I mean, I was told numerous times that, well, it’s kind of an expensive sample, so we only test if we think there’s a problem. But at the same time, what are we testing I think makes a big difference. I’ll let you respond to this. I don’t, I know you like to know what’s in the corn silage by itself. I really don’t care. I wanna know what is going in the cow. I want the TMR. Am I wrong for that?
Dr. Larry Roth
No. I think that sampling the TMR certainly makes sense. Especially if we’re feeding a variety of byproducts.
Scott Zehr
Yeah.
Dr. Larry Roth
Especially depending upon the source of our corn.
Scott Zehr
Yeah.
Dr. Larry Roth:
Are we doing a high moisture corn? Are we buying corn from the local elevator? Where is that corn coming from? And then we put all of that together and we’re able to test the TMR what the cow was actually consuming.
I think it’s good to watch the corn silage because so often that is a major source of our mycotoxins as corn silage makes up greater and greater proportions of the diets being fed. So certainly corn silage makes sense. But TMR is absolutely where we’ve got to start.
Scott Zehr
I think you’re right. I think testing the TMR is a good place to start. And Larry, I, I like the, this idea of a checklist, right? So I’m gonna ask you the listener, the question, have you tested your silage or TMR within the last 90 days? If you haven’t [email protected]. And I’ll like be glad to send you resources to do it. Talk to your nutritionist. Ask yourself this question, am I seeing unexplained health dips?
Now, that’s a, Larry, I wanna dive into that question a little bit because, unexplained. How much time do you think was spent in those nine months, explaining, you know, I’m referencing back to that dairy that ultimately had a toxin issue. How much time do you think was spent explaining why cows weren’t getting pregnant and we blamed everything under the sun?
Dr. Larry Roth
Yeah.
Scott Zehr
And, you know, it goes back to an old theory that I have. It’s when two plus two doesn’t equal four, it’s probably toxins. You know, sometimes things we think they’re not able to be explained when in reality they are. I guess I’d like your take on that too.
Dr. Larry Roth
Well, I think a good place to start is the mycotoxin assay is not that expensive, especially when you have a company that’s ready to pay for it.
Scott Zehr
Yeah.
Dr. Larry Roth
Number two. Think of all of the consultant time, veterinary time, dairy producer time that goes into trying to troubleshoot a situation when really a relatively inexpensive mycotoxin assay could have eliminated a lot of the situations in that case study that you were talking about. So, some routine testing for mycotoxins, for nutrients can reduce the unexplained occurrences that you were talking about.
Scott Zehr
I always like to say, you know, even if you paid for it outta your own pocket, let’s just use a round number of a hundred dollars to do the test. Spend a hundred dollars now, lose a hundred thousand dollars in milk.
Dr. Larry Roth
Absolutely. Yep. Yep. So for a hundred dollars sample, how much milk would I need to sell to pay for that? Not very much. Yeah, exactly.
Scott Zehr
You know, if you go back to the DTX study where they picked up two and a half pounds of milk by taking care of a DON and zearalenone challenge. And $20 milk, that’s $182,000 a year on a thousand cow herd.
Dr. Larry Roth
Yeah.
Scott Zehr
You know, obviously you have cost of the mitigation, but, Larry, I, hope people walk away today challenge to incorporate this. You know, if you’re a nutritionist listening, and you’re not currently leading the conversation and being the first one to say, Hey, we need to have a routine sampling program, whether it be monthly, bimonthly, or quarterly.
Checking the TMR and again, I’m gonna put a little plug in Larry. Don’t forget the dry cow TMR. Don’t forget the prefresh TMR. Check ’em. Be that person. If you’re a dairyman listening to this episode, challenge your nutritionist a little bit. Tell ’em, Hey, I want routine sampling because I can’t afford nine months of trying to figure something out. You know, that could have just been traced back to a test.
Dr. Larry Roth
Scott, you mentioned dry cows and pre fresh. We’re seeing a lot of wheat straw samples this year that are high in both DON and zearalenone. And what’s increasingly being fed to dry cows and pre fresh cows? Wheat straw.
Scott Zehr
Yeah. Yeah. I think this is good. I like the fact that we do this. We have this sampling program available for everybody. I think the data is important that you’re sifting through. I think it gives us a good overview of things to look for in our region, whether it be fumonisin may be more prevalent in areas or zearalenone or DON.
But at the end of the day, folks, like it’s about, you know, giving you something tangible that you can use to defend, and protect your cows, right? So Larry, if I guess as we wrap up, give me your back of the napkin three point action plan here.
Dr. Larry Roth
First of all, I’m gonna encourage people to do monthly testing. Depending upon the size of the dairy and amount of byproducts making up the diet. Maybe we don’t have to go quite as often, but I would look at monthly testing. Number two, let’s already start making plans for testing corn silage next year.
Number three, let’s look at unexplained occurrences happening. Be it fresh cow issues, whatever changes that come up instantly we start thinking about testing our rations. So it is relatively simple to put this into place. It becomes a monthly occurrence that we’re testing our feeds going into storage to know what is happening.
Scott Zehr
Yep. I like that. Well, Larry, I want to thank you again for jumping on here today. You know, my closing thought is please make this standard operating procedure number one, folks. So, and I agree with Larry on this. Appreciate you taking the time again today. We’ll be talking to everybody again in a couple of weeks. Thank you.
Dr. Larry Roth
All right. Thank you, Scott.
