Mycotoxins in young stock diets can hinder growth and performance by triggering an immune response that diverts nutrients away from productive purposes. When calves face additional stressors like poor passive transfer, ventilation issues, or pathogen exposure, mycotoxins amplify these challenges, making it harder for them to thrive.
Despite their impact, mycotoxins in starter feeds often go undetected. Implementing a routine mycotoxin sampling program can provide important information to help refine nutrition strategies and optimize calf development.
In this episode, Dr. Larry Roth, Vice President of Nutrition, discusses how mycotoxins affect calf health and the best ways to manage their impact.
🎧 Listen now to set your herd up for lifelong success!
Scott Zehr
All right. Welcome everybody to another episode of Ruminate This with Agrarian Solutions. I’m your host Scott Zehr. And today we are going to be talking with Dr. Larry Roth, vice president of nutrition here at Agrarian Solutions. And Larry, what we’re talking about today is I know something near and dear to your heart, mycotoxins.
But in particular, I’d like to pick your brain a little bit today on specifically a portion of the animal’s life that we really don’t ever think about mycotoxins or doing something about mycotoxins and specifically in the pre weaned calf. And then, you know, maybe we can talk about some of the virgin heifer population that, you know, the post weaned stuff too. But yeah, thanks for coming back on the podcast today, Larry, and,
Dr. Larry Roth
Glad to be here.
Scott Zehr
So, I, guess my first question would be, should we be concerned about mycotoxin mitigation or the damages that mycotoxins can cause in pre-weaned calves?
Dr. Larry Roth
You bet. That’s a fantastic question. The short answer to that, should we be concerned about mycotoxins in the pre weaned calf? The answer to that is yes. And then the question is, why should we be concerned about it? And I think the simple answer to that is mycotoxins change nutrient allocation.
So, Scott, we can talk about the price of milk replacer formulations and we can go through that. We can talk about starter feeds and so forth, but we think about starter feeds being a source of mycotoxins. Because we’ve got so often byproducts there that are concentrating the level of mycotoxins that were present in the base feeds that the byproducts came from.
But you’ve got a young animal, in many respects are pre ruminant. The rumen, that great fermentation that can break down some mycotoxins is not developed. And so we should be thinking about the pre wing cap as being, in some ways, almost more similar to a broiler chicken or a feeder pig than to the lactating cow that it will eventually become or the feedlot deer that it might become.
Scott Zehr
So, you know, you mentioned the rumen right now being developed and we’re feeding it a starter feed to develop the rumen that could potentially have mycotoxins in it. What kind of inhibiting factor does that maybe blend?
Dr. Larry Roth
You bet. So again, it all comes back to defending and protecting the right nutrient allocation. And that can be as simple as nutrients are going toward proper immune function and going toward growth with the pre weaning calf. Now, if we have mycotoxins attacking the small intestine lining and destroying cells, now the calf’s got to put nutrients into repairing the small intestine.
Well, that’s nutrients that didn’t go toward growth. That’s nutrients that didn’t go toward developing internal organs that produce enzymes to help break down the diet. That’s a reallocation of nutrients that otherwise could go to even developing the rumen lining. So I’m just, I’m thinking here, Scott, that mycotoxins attack the small intestine lining.
They may be attacking the rumen lining and the body has to repair that damage. And then has to also deal with anything that the mycotoxins might be doing to the liver and the body’s biochemical factory.
Scott Zehr
So, treat me like I’m a calf manager on a dairy, you know? And, and Larry, what are some of the challenges that I should be looking for or maybe signs that this could be an issue?
Dr. Larry Roth
You bet. A fantastic place to go. How would I know if I have mycotoxin issues with my calves? Are your calves meeting your weight goals at weaning? Or how much starter feed is that calf consuming at weaning? Tell me about incidents of antibiotic treatments, electrolyte treatments. Tell me about calf survivability. Because if we’ve got mycotoxins present and changing the allocation of nutrients because we’re damaging the small intestine and we’re impairing function of the liver, all of those other items are going to suffer.
Calfs aren’t going to weigh as much as they should. If calves aren’t growing, they’re not eating as much starter feed. If the calf doesn’t feel well, because it’s got other health issues, because the immune system is drugged down, dealing with the unresolved inflammation from mycotoxins, it’s not going to consume as much feed.
If we have a high incidence of antibiotic treatments and electrolyte treatments, a lot of respiratory and digestive scours going on, well, that could be due to the immune system’s having to deal with all the mycotoxin related inflammation. So tell me about your calves, Scott. Tell me how they’re doing. And if they’re not performing up to your expectations, let’s start doing a little bit of troubleshooting to see what might be going on.
And, you know, over the last year, we’ve been testing quite a few starter feeds around the country. And some of these have been showing up relatively high in mycotoxins. And I think that’s principally due to byproducts concentrating the level of mycotoxins in the base stock grain or whatever is being used to produce the byproduct.
Scott Zehr
So two questions that, you know, I think about with that comment is one, what is a concerning level in starter feeds, considering these small bodied animals. And two, they’re not eating a lot of feed, right?
They’re not eating a lot of this grain. Starting out, you know, there might be eating a mouthful a day. You know, we’re trying to get them up to four or five, six pounds, but, even then, it’s not like they’re eating as much as a mature cow.
Dr. Larry Roth
Exactly. Yeah. Well, how’s this for an answer, Scott? I don’t know. I don’t know because what other factors are the calves having to deal with? You know, with the cow side, we talked about herd indicators.
Scott Zehr
Yeah.
Dr. Larry Roth
We talk about things like overcrowding. We talk about comfort. We talk about disease, transition issues. We talked about what some newer look like with cows. We should be asking the same question on the cap side.
Because if the cap has a good dry situation where it can lay down, it’s not dealing with the cold, not dealing with the wind, that calf can probably handle a higher level of mycotoxins. It’s got more nutrients to throw against this problem. But the higher the mycotoxin incidence, the more nutrients are drawn away from productive purposes, the more likely we are to see some of these other challenges.
So, not to dodge your question, Scott, but I don’t know. Is that we really know? But if we watch our calves and their performance isn’t what it ought to be, then we start doing the troubleshooting. And a place we need to look is that stratigraphy. What are the levels? And I think, you know, if we start, like, say one PPM at dawn you know, I, I think we start to get where we need to be concerned about things?
And then we have multiple mycotoxins, multiple challenges are put upon the calf. So that’s not to dodge your question, but I think it’s to truly address what we need to be looking at with the calf. We need to be thinking about our management, if we’re group housed and calves are a little bit challenged for getting up, having enough time to go up and nurse from the automatic feeder. You know, it’s just not good aerial environment there.
The bedding’s wet and so forth. That calf is probably going to be more susceptible to mycotoxin issues at a lower level than if the calf was in a man, almost ideal type situation. Scott, you asked a very important question. I don’t know is that we really know that level.
Scott Zehr
Well, it certainly begs the question to me. A question that I love asking. I ask you this a lot. What if?
Dr. Larry Roth
Yeah.
Scott Zehr
You know, so, okay, we, have 90 percent of our calves wean on time at the right weight. We get them weaned, we get into this awkward kind of post weaning before they’re really ready to take off on a TMR. A lot of times we see them go backwards.
I mean, that’s very common in herds. It kind of, you see these big, beautiful weaned calves and go look at that same group a month later. And it’s like, have they really done anything, kind of thing? So what if? What if we made it routine to evaluate the diet going into that pre weaned calf?
Dr. Larry Roth
Nope.
Scott Zehr
Is there a possibility we get 99 percent success weaning, hitting our targets, 95? What kind of impact does that carry on down the road?
Dr. Larry Roth
Absolutely.
Scott Zehr
If she’s a late, you have a calf that doesn’t wean on time. And if your program is to hold her back to the next group, now, there’s social stress. There’s a hierarchy of dominance within that next group because they’re a little bigger. If you push her through and she’s not ready to take off, how many of those 10 percent of calves fall out of the program before they ever freshen?
Dr. Larry Roth
Yeah. So, that’s where I come back to tell me about your calves. And if 10 percent of them aren’t weaning on time, why is that? Why is that? And is there something that we can relate back to the starter feed being a source of mycotoxins. Let’s maybe approach it from a little bit different angle. Let’s just say that during the dry cow period, the cow was consuming a ration that had some mycotoxins in it.
Some of those mycotoxins may pass through into that colostrum. If she’s having to deal with mycotoxins, she’s not going to produce the colostrum quantity and quality that we want. So you see how this whole thing can kind of snowball. And we have to be thinking about what’s the role of mycotoxins all the way through. And I’m not saying mycotoxins are always the problem in every situation. But, they need to at least be considered. At least be considered.
Scott Zehr
Well, and right, the epigenetic discussion, you know, what happens with that cow when she’s in utero with a calf? Everything that’s negatively impacting her impacts the developing embryo, impacts the developing gonads of that offspring. It’s a 3 generation multi-effect and.
I mean, Dr. Britt was on here last year talking to us about that. You know, Larry, I think a number that’s gotten a lot of attention over the last number of years, especially as beef on dairy has taken off in the U. S. Dairy market is non completion rate at Virgin Heifers.
And I mean, yeah, we always want to be, in a perfect world, we’d be at one to 3 percent non completion rate. But in reality, there’s a lot of farms running 10 to 15%, sometimes even higher.
Dr. Larry Roth
Yeah.
Scott Zehr
What would you say to those farms to challenge them to Maybe think outside the box a little more? That just looking at more angles and more, you know, what’s what should they be really trying to do?
Dr. Larry Roth
Why do you think your non completion rate is where it’s at? What do you think are some of the weak points? The cow that has a difficult transition period may very well I’ve had a difficult pre weaning period may have had challenges that weaning. And why was that? Were there some pathogen issues pre weaning? Some respiratory issues? Could some of those be traced back to mycotoxins?
So, I guess, I don’t mean to sound like a politician, mycotoxins may have a big role, they might not, but they at least need to be evaluated. They at least need to be evaluated, and it’s relatively simple. We need to know what’s going on with dry cows. We need to know what’s going on with our lactating cows if we’re feeding some of the waste milk to the calves. Do we have some of those mycotoxins passing through in the milk and then causing issues with our calves?
Scott Zehr
You know, I think something else to consider as well is like. So, Dr. Billy Brown from Kansas State joined us the first part of the year here in 2025 talking about developmental program. I mean, if these calves are going through an insult, whether it be pathogens, whether it be mycotoxins, poor management, facilities, I mean, there’s gene expression that gets turned off. Like, these animals are never going to be the same, right?
You know, I keep coming back to this idea in my former life. One of the gentlemen at 1 of the stud companies, made reference to the, I think the highest possible net merit that we know of was, and I forget what it is now. It’s, it’s in the thousands. You know, just hypothetically for the discussion, let’s say it’s 5000.
Dr. Larry Roth
Ok.
Scott Zehr
And we’re at 1,300, 1,500, 1,600. There’s a lot more things that we don’t know that these animals can do.
Dr. Larry Roth
Ok.
Scott Zehr
And, you know, this big black box that is the research side, the university research side in calves, there’s a lot of work done on calves of starter feed, what’s better. High starch, high fiber, a lot of formulations of milk replacers. There’s nothing in the way of what are mycotoxins doing? And part of it is it’s a really long research project, right? I mean, how do you track this group of animals?
Dr. Larry Roth
Yeah. And there’s that aspect to it, Scott. But how many research studies that are evaluating, let’s say, milk replacers, what level of fat, what level of protein, what level do you need to be feeding? Do they measure mycotoxins in the milk or the starter feed? Hardly any. I don’t know of any that do that.
How about research studies that are evaluating pellets versus a textured feed? How many of those studies measured mycotoxin levels? Are we really evaluating the form of the starter feed? Or are we evaluating which form brought in more mycotoxins? So there’s a whole lot of questions, I think, Scott, to be asked in that area.
And so it’s doing the completeness in the study that we know what else is going on. And I’m not saying that mycotoxins are the reason that every calf doesn’t perform the way that we think it should.
Scott Zehr
No, absolutely.
Dr. Larry Roth
But, it’s something that needs to be evaluated and something that we need to know.
Scott Zehr
I think just like anything, you know, Larry when I would go to farms and do dairy comp analyzation, you know, looking at farm records. Well, if you don’t track it, I can’t consult on it. I can’t give you any insights if there’s no recordings of it, right? And I like to communicate the same thing to nutritionists and dairy farmers today.
Why we believe in a routine sampling program? If we’re not routinely tracking the toxin load that’s in the TMR, how can we give advice on it? And so I would, I would almost challenge people to be thinking about that more with the calves. Like you said, it’s definitely, I don’t want people to think we’re, we’re preaching doom and gloom here because we’re not. Mycotoxins aren’t going to be probably the most contributing factor every single time. But are they a contributing factor?
Dr. Larry Roth
Are there situations where they could be? Let’s rule it out.
Scott Zehr
Yeah.
Dr. Larry Roth
Scott, we go to a calf raiser and health isn’t what it should be. Have they evaluated their starter feed? Have they evaluated whatever they’re using for milk to make sure that this is not an issue? Because we could be chasing all of these other issues. And god darn it, performance just hasn’t improved. Because we didn’t address the main factor.
Scott Zehr
Well, I think the other side of that too is we address these other factors and performance does improve, but marginally we don’t hit that level that we thought we could.
And Larry, if I’ve said it once, I’ll say it a hundred times. If one plus one doesn’t equal two, go look for mycotoxins.
Dr. Larry Roth
Yeah.
Scott Zehr
So, Larry, I’m going to ask you a Dr. Larry Roth question here. We have mycotoxins potentially affecting calves. So what? What do we do about it?
Dr. Larry Roth
You about? So what? We have mycotoxins affecting our calves. Well, it’s going to determine the type of cow that we’re going to have at some point. It’s going to determine the type of feedlot animal that we have at some point.
Scott Zehr
Yeah.
Dr. Larry Roth
So what? We got mycotoxins. Well, is it setting our calves up for more health issues, pre and post weaning? So what? We got some mycotoxin issues. Is it dragging the calves immune system down so that Crypto or Coxy is getting a little bit more of a hold on the calf so that weaning comes along and they go backwards on us because of that?
One of the big issues right now with beef on dairy calves, and I think should be an issue with native type feedlot animals: liver abscesses. If mycotoxins are causing a break in the castle wall, the small intestine lining or potentially the rumen lining, is it setting that animal up for liver abscesses? Potentially, could be.
You know, again, the dogma back in the last century, and you’re talking to somebody who graduated from University of Nebraska, what it was acidosis U, we assume that liver abscesses were due to ruminal acidosis. Okay? But what if being a native beef steer or a beef pond dairy animal has some scours or has mycotoxin issues pre weaning, is that animal set up for liver abscesses at that point?
Let’s look at it another way. Very interesting study in the Journal of Animal Science several years back. My good grief, it was about 10 years ago now. Went to a slaughter facility in the Midwest. And it was about 35%, the cold dairy cows going through this facility has significant liver abscesses. Wow.
Scott Zehr
Yeah.
Dr. Larry Roth
Well, again, if dogma is, it’s ruminal acidosis that causes liver abscesses, were these cows really getting ruminal acidosis? I don’t really think so. Maybe subacute, but probably not a severe ruminal acidosis could be. But 30, 35 percent of them? Could these liver abscesses have been initiated pre weaning? Potentially.
So the liver is the body’s biochemical factory, liver abscesses mean our factory isn’t working at the level that it could be. So why were these cows culled? Were they culled because they wouldn’t breed back? Were they cold because of transition issues?
Scott, I can make the case physiologically, metabolically, that the cow who doesn’t breed back could potentially have liver issues. I can make the case physiologically, metabolically, that the cow having transition issues could have an impaired liver. And it all goes back to pre weaning.
Scott Zehr
Yeah.
Dr. Larry Roth
Congratulations, Scott. You’ve done the best job in the world genetically with your herd. Congratulations. But if we have some mycotoxin issues or pathogen issues, pre weaning, damages the castle wall, the small intestine lining, be it pathogens, be it mycotoxins, impair liver function to the point where we get some liver abscesses, are your animals ever going to reach their genetic potential?
Scott Zehr
Well, I think that’s the question, right? That we want to leave people with is think about the long term. You know, impacts here. But also, our colleague Jeff Hostetter just mentioned that the Pennsylvania Dairy Summit this past week, there was a discussion on what is it going to take to get to the eight pound club, right? And stay there consistently.
Again, I’m going to go back and say there’s a lot of things that we are learning on how to feed the rumen better. There’s things that we’re learning to make these animals more efficient, more efficient use of their nutrients. And, I just think that, you know, if, until we started dressing these calves more closely and subsequently virgin heifers up to calving, Larry, I’ve said it before, these animals are no longer a commodity in the U. S. Let’s not treat them like one.
Dr. Larry Roth
Absolutely.
Scott Zehr
And good job to you, you old podcast pro doing a callback for us, talking about the liver abscess. So if you’re paying attention, that’s episode 6 where Dr. Roth and I talked about why do liver abscesses plague both dairy and feedlot cattle? So, good job, Larry. Good callback.
Dr. Larry Roth
There you go. It’s all one big cycle.
Scott Zehr
Yes, it is. You know, I think you’ve given the audience something to consider. And you know, from I guess a call to action standpoint, if you are listening to this podcast and you want to contact us it’s [email protected], reach out to us, we’ll help you get a sampling program going on your farm, whether it’s dairy, beef, doesn’t matter.
And if you’re in academia listening, Larry mentioned how there’s a lack of testing in that research world. Get a hold of us. We’ll partner up. Larry, is there anything you’d like to leave our audience with today?
Dr. Larry Roth
You know, Scott, our main topic was mycotoxins and their effects upon calves. Mycotoxins are not the only challenge for the calves. But if we’re trying to get the best performance out of our calves, both pre weaning and longterm, let’s do the troubleshooting. And one of those troubleshooting items has to be, are we dealing with mycotoxins?
Scott Zehr
Yeah, I just think so often it’s there’s so much value in just eliminating the things that it’s not.
Dr. Larry Roth
Yeah. Absolutely.
Scott Zehr
So, Dr. Roth, I did think of one more question, right? So, within the Agrarian toolbox within our portfolio, how can we help defend and protect these baby calves?
Dr. Larry Roth
Fantastic question. So we identify mycotoxins are an issue. So what are we going to do about it? Well, that’s where I think our first of all, our day one calf gel or calf bolus, depending on which a person likes, inoculate the track with beneficial bacteria, outcompete the pathogens, bring in the egg-based pathogen focused proteins to take those organisms out, eliminate them as a potential problem because we’re trying to build the integrity of the castle wall, the digestive tract lining, make it more resistant to mycotoxins.
And then on a daily basis, supplement our big calf powder. BIG stands for bacteria and, I can’t say it, but the eggbased pathogen focused proteins. Yeah again, it’s all about what can we do to build up the integrity of the castle ball so that is more resistant to the mycotoxins. That’s what I would be doing.
What can I do control pathogens so they’re not damaging the small intestine themselves? Anything that helps that calf be stronger, have a better immune system is going to set it up to better handle mycotoxin-related inflammation. You’ll note, Scott, there’s something I did not mention, and that’s the DTX.
We can’t mention the DTX. We can’t mix the DTX into the calf powder because some of it’s going to settle out. We can’t pellet the DTX, because the pelleting so often is at a high enough temperature is going to kill our bacteria. So at this point in time, I would look at inoculating the tract at birth.
Replenishing the bacteria anytime that we have to do an electrolyte or antibiotic treatment, go back to the gel or bolus, depending on the preference. And then on a continual basis, be supplementing the big calf powder. Do everything we can to strengthen the digestive tract lining, control the pathogens and enhance immune function to deal with any mycotoxins that might be coming along to cause challenges.
Scott Zehr
That’s a great point, especially on the DTX. Plus you have such an inconsistent feeding intake of starter grain during that pre weaned phase, right? From just a little bit to multiple pounds. But I appreciate that insight and I would just mention to people too that the program you just talked about with the day one gel or the, in conjunction with with big calf, I mean, we’re, we’re looking at a $15 investment in an animal for the whole weaning phase.
Right. It’s pretty marginal in the grand scheme of things. Well, Dr. Roth, I definitely want to thank you again for taking time out of your day to join us on Ruminate This. And I think we’ve given the audience something to think about.
And I’ll say it again, [email protected] if you have any questions, or would like to talk to us about implementing a routine sampling program on your farm. So with that, we will see everybody again next week.
Dr. Larry Roth
All right. Thank you, Scott.
Scott Zehr
Thanks, Larry.
