Summer heat stress in dairy cattle is about far more than fans and sprinklers. In this episode of Ruminate This, Scott Zehr and Dr. Larry Roth discuss the hidden biological effects of heat stress in dairy cows, including inflammation, leaky gut, oxidative stress, altered blood flow, and immune disruption. They also explain why heat stress should be viewed as an inflammation challenge rather than simply a temperature problem.
The episode also explores how DTX™ with Livox uses probiotic technology and plant actives like curcumin, naringen, and carnosic acid to support dairy cows during periods of heat stress. Learn how internal biological support may help cows better withstand the stacked environmental insults of summer while supporting health, performance, and resilience.
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Scott Zehr: All right, welcome everybody to another episode of Ruminate This with Agrarian Solutions. I’m your host, Scott Zehr. And today I’m gonna be joined by Dr. Larry Roth, the Vice President of Nutrition here at Agrarian Solutions. And Larry I’m hoping to have a really good discussion today with you on the topic of heat stress.
However, I’m gonna challenge you a little bit because this topic has been covered a lot in our industry, obviously. This is a north of a billion dollar economic impact in as far as loss is concerned in the US dairy industry. But I think we’ve heard enough in the past about sprinklers and fans and so on, that I have a different take that I’d like you to explore with me today.
Dr. Larry Roth: Okay.
Scott Zehr: And so with that, I guess, welcome, Larry.
Dr. Larry Roth: Good to be here.
Scott Zehr: All right. Dr. Roth we’ve been taught about this a lot over the years, as I mentioned. And I think we’ve almost been taught to think about heat stress as the problem. But based on what we’re seeing now, is it more accurate to say that heat stress is actually exposing everything else we don’t control?
Dr. Larry Roth: I think that would be fair to say. It is another stressor. Sometimes we use the term, Scott, stacked stressors. And so it, shall we say, exacerbates other challenges going on. If our diet, for an example, is kinda marginal in terms of readily formidable carbohydrates, and we’re at risk of subacute acidosis, and now we got heat stress, and it changes eating patterns. It may cause the cows to experience some periodic subacute acidosis, which if the temperature was 20 degrees Fahrenheit and the cows were eating more consistently, would not be an issue. Yeah, so we could go on with other examples, but I think it would be fair to say, Scott, that heat stress is another stressor that we stack on top of everything else with which the cow is dealing.
Scott Zehr: Yeah, and I, I don’t want the audience to be confused. I’m not saying that heat stress is not a problem in and of itself. But I think that the deeper layer is that all by itself it’s maybe not as problematic as when we have all these other stacked things going on that the heat stress then exacerbates, like you said.
Dr. Larry Roth: Yeah. Fair enough. Fair enough.
Scott Zehr: Yeah. So when you look at things like heat stress, mycotoxins, intake disruptions, are these additive problems or are we actually dealing with more of a multiplicative effect inside the cow?
Dr. Larry Roth: Oh. I think that we may be dealing with more of a multiplying effect. Especially dependent upon how many stressors there are. And when we use that term stressor, I think it’s important, Scott, to say we’re not implying mismanagement.
Scott Zehr: Yeah.
Dr. Larry Roth: We’re just saying that we’re asking this cow to do a lot. She’s gotta live in a real world situation, eat real world rations, live in a real world freestall barn. So we’re not implying mismanagement. But I would say that…
Scott Zehr: No, and I think the better term is probably environmental insult, right?
Dr. Larry Roth: Yeah, there you go. Yep.
Scott Zehr: Yeah. No, and I don’t think, you look at the management practices across the US dairies, we’re- we’ve figured out how to manage groups of cows extremely well and- Yes … and, what we’re looking at here today is the relationship between those environmental insults and mycotoxins. And really again just trying to reframe this conversation in a way that, essentially how do we take this to a step where we can’t control the weather, but here are the environmental insults that we can control, right?
Dr. Larry Roth: Yeah.
Scott Zehr: So I guess going– you mentioned mycotoxins, so specifically speaking to that, to the mycotoxin challenges, what changes inside the cow during a heat stress event that would potentially make a manageable mycotoxin load all of a sudden a much bigger problem?
Dr. Larry Roth: Okay, fantastic question. What’s that interaction between heat stress and mycotoxins? When cows are heat stressed, they go through a couple of changes. One, increased respiration. They’re getting rid of more moisture, and they also cause greater blood flow to the extremities to radiate heat away, much like the radiator on your truck tends to send engine heat off to the environment.
So all of that is reducing blood flow to the digestive tract. And then the digestive tract needs a tremendous amount of blood flow to provide nutrients for the turnover in cells to also keep those cells alive. And to pull nutrients that are absorbed into the bloodstream to go to different parts of the body.
So if we’re losing moisture through the lungs, and we’re shunting blood flow more to the extremities to radiate heat, what ends up happening is our intestinal lining cells can become dehydrated. They tend to shrink. And we talk a lot about the tight junctions between the cells. It’s like the mortar that holds the castle blocks together so that the barbarians are kept in the digestive tract and out of the body.
So if our intestinal cells start to shrink, we lose our tight junctions. Now we’ve got interstate highways for pathogens, mycotoxins, all of this bad stuff to get through the castle wall, the intestinal lining, and into the body. Flows through the bloodstream, ends up in the liver, the body’s biochemical factory not just processing nutrients, but also getting rid of toxins.
So now we got an extra load on the liver which, depending upon the stage of production, is maybe processing a lot of fats that have been broken down in that early lactation cow. And at any stage of lactation, just doing a tremendous amount of work to make glucose so that we have glucose to make lactose for milk sugar serve as a carbon source for rapidly developing cells like the follicle and the embryo. So it’s, it is a cascading effect.
Scott Zehr: As I’ve heard you say many times.
Dr. Larry Roth: Yep. Yeah. Intestinal cells are short on water, they shrink, and now everything starts to go downhill from there.
Scott Zehr: Larry, the cascading effect, we’ve talked about the downstream effect of a lot of these things over the last number of episodes here. But also you mentioned the liver making glucose, and I think there’s always room for one of the famous Larry quotes that I’ve heard a number of times which is, “No glucose, no lactose. No lactose, no milk.”
Dr. Larry Roth: There you go.
Scott Zehr: And uh, so, you know, as right at the downstream side of that is we see a lot of decreased milk production during heat stress events and essentially we’re just not keeping up with that process, right? ‘Cause we’re diverting stuff to other purposes. So you’ve had the chance over the last shall we say- couple of decades at least to…
Dr. Larry Roth: Nice way to put it.
Scott Zehr: To spend a lot of time not just talking with dairymen and talking with nutritionists, but actually being on farm and seeing the operations and understanding the management.
But when you walk into really high-performing dairies, what are they doing before summer hits that average operations wait too long to address?
Dr. Larry Roth: Okay. That’s a fantastic question. What are the high-producing dairies doing to get ready for heat stress? They know it’s gonna happen. And Scott, it can be as simple as fan maintenance.
Blades are clean, motors are ready to go. Sprinklers, all of the plumbing is right. But we don’t have leaks so that we don’t have too much water flowing where it shouldn’t be, filling up the lagoon. Comfort, the freestalls are bedded right. Curtains are up. We don’t let the sun shine in, but we also want to have air movement taking place.
With cross-ventilated barns, all of the fans are working right. We know that summer is coming. We’re just making sure that everything’s ready to go. Also looking at different feed additives that people are looking at. Things such as betaine and osmolyte to keep water in cells. People are also looking at capsaicin coming from peppers, which excuse me, hot peppers, which can increase blood flow to the extremities.
And I think, Scott, we should be looking at DTX, our cell-wall-deficient bacteria technology that helps to protect digestive tract integrity and what we’ve done with plant extracts that help to protect the intestinal lining cells and also to protect liver health. So it’s a combination of factors.
And I would say over the last number of decades, number one, we’ve recognized that heat stress is an issue. We’ve said that we gotta do something about it and become proactive. Even just consider, Scott, how we design freestall barns now.
Scott Zehr: Yeah.
Dr. Larry Roth: Consider the cross-ventilated barns, the number that we see. So the industry does stand to have a significant financial loss to heat stress, as you mentioned. But the industry is also making a tremendous investment each year to reduce that loss to heat stress.
Scott Zehr: Absolutely. I love the fact that you brought up the fans first. I’ve probably told you before my dirty fan theory, which is you walk into a barn in the middle of February, and if the fans are dirty, maybe they’re letting other things slide, too. And…
Dr. Larry Roth: There you go.
Scott Zehr: I’ve walked into a number of barns in February where the fans are spotless. There’s not a drop of dust on those blades. Those farms tend to not miss a beat. They have mastered the fundamentals.
And continue to keep up with them. Everything you just described there, Larry is all things that the dairy has for the most part within their control, right? Taking care of water situations, sprinklers, fans…
Dr. Larry Roth: Yeah.
Scott Zehr: maintenance, stall care. How often do we see, it’s springtime, I get it. We have planting, we have, we’re ramping up to get ready for first cutting. And the beds didn’t get sanded this week because we just couldn’t spare a person.
Dr. Larry Roth: Right.
Scott Zehr: And it’s just, it’s a recipe for disaster. and so many times these conversations come down to fundamentals and doing things the right way every day, every time. But I think, a- again, it’s like heat stress is a problem. Don’t let it be a bigger problem than what it is, right?
And you mentioned the DTX which is our mycotoxin mitigation product here at Agrarian, and I’m gonna ask you more questions on that in a subsequent episode. But I think the big takeaway that I’d give to producers right now, Larry, is for the first time in my lifetime, there is a research-backed mitigation tool, mycotoxin mitigation tool that is appropriate for the mycotoxins we see in today’s herds.
And we manage so many other things on dairies, some of them extremely well. Here’s a tool for us to look at and say, “Can we just take mycotoxins out of the conversation for now?”
I guess just to reiterate what you said recently, your last comments here, if a producer’s talking to you and you’re a nutritionist and they’re just saying “I can’t control the weather,” maybe just give us three things that you would push back and say, “No, but here are the top three things you can control and are responsible for.”
Dr. Larry Roth: Wow, top three things. I would have to start with ventilation, air movement. Number two would be sprinklers to help wet the cows. Number three, the feed additives so that we can work from the inside out with cows. And you said three, so I gotta stop at that point.
Scott Zehr: Okay. But,
Dr. Larry Roth: but-
Scott Zehr: if you have a couple bonus ones, that’s okay, too
Dr. Larry Roth: I think how we take care of the freestall beds-
Scott Zehr: Yeah.
Dr. Larry Roth: comfort. Because-
Scott Zehr: Yep.
Dr. Larry Roth: When it’s hot, cows tend to stand a little bit more, so that’s extra stress on the feet and legs. And cows tend to make more milk when they’re laying down, and there’s a variety of reasons for that. So general cow comfort, and you mentioned water availability. I didn’t mention that before, but I think that is absolutely key.
Scott Zehr: Yeah. Larry I think as we wrap up here, we started the episode talking about stacked, we’ll call it, we’ll say insults, right? And we have-
Dr. Larry Roth: Okay.
Scott Zehr: We’ve talked mycotoxins, we’ve talked heat stress. But also I think there’s maybe some other things that sometimes come into play that we don’t always think about because they’re routine things we have to do, like pen moves, hoof trimming routines, all these kinda normal processes that happen that just add an additional layer to these cows.
And I’m not saying don’t hoof trim during the summertime, but be aware of maybe there’s a way we could look at the weather and say, “Hey, it’s gonna be 15 degrees cooler at the end of the week. Can we move some things around sometimes?”
Dr. Larry Roth: Yeah, that’s right. Can we postpone certain animal movements and so forth until the weather cools down, like you said, this weekend? When the temperature’s gonna go down 15 degrees as opposed to today. So it, again it’s thinking how is this particular item going to affect the cow today? Is this something that I should delay a little bit? Is this something that I should do a little bit differently to minimize the challenge that’s put on the cow?
Scott Zehr: Yep. Yep. One of the saddest things I’d ever seen on a dairy, it was a move from one farm to the other, and it was summertime. And Larry, what could go wrong with 10 cows on a trailer that have to go 30 miles?
Dr. Larry Roth: We get a flat tire, and it’s 100 degrees, and they’re not getting the ventilation and so forth. Yeah.
Scott Zehr: Yep. Final takeaways, Larry?
Dr. Larry Roth: Heat stress is gonna come. What are we doing to get ready? Make our checklist, have our strategy in place, and be prepared to enact that strategy.
Scott Zehr: That’s right. Control what we can control. I like it. Yep. All right. Larry, I’m gonna bring you back for a little more in-depth discussion on what all DTX is actually doing to help the cow from the inside out, on another episode. So with that, I wanna thank you for taking time out of your day to visit with us, Larry, and we’ll be talking again soon.
Dr. Larry Roth: All right. Pleasure to be here. Thanks, Scott.
Scott Zehr: Thanks, Larry.
