The Moos Room™

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Brad Heins: Welcome to The Moos Room. Today, it's just Brad. Emily is out doing some Extension-related activities, and Joe, I don't even know where he's at. He's across the pond in Scotland or Ireland or something having a great time while we're here in hot Midwestern Minnesota, but I have a guest today. We have a guest on the podcast that will be talking about some activities today. Our guest is Bethany Dado-Senn from Wisconsin.
Welcome, Bethany.
Bethany Dado-Senn: Thanks so much for having me.
Brad: We're going to talk a little bit about heat stress in dairy calves but first, we will ask our super-secret questions to all of our guests like we do. Sorry, I do not have the tallies. Joe doesn't allow me to have those. The first question will be, what is your favorite breed of beef cattle?
Bethany: [chuckles] You threw me there. I figured you were going to ask what breed of dairy cattle, given your background, but my favorite breed of beef cattle would be the Charolais because they just make the cutest little beef on dairy crosses.
Brad: Charolais. We will accept that answer, yes. We haven't had many Charolais responses, so it's always nice to get a different response. There is lots of choices. Over the last few years we've been doing this, we have maybe 30 to 40 different beef breeds that people have mentioned, so there's a lot of beef breeds.
The second super-secret question you probably have already picked out, what is your favorite breed of dairy cattle?
Bethany: Oh, there it is. Okay. Well, if I have to guess the right answer, I think that'd be hard with all of the crossbreeding that you guys do. I'm going to say for the sake of today's discussion, heat stress in calves, I would pick the Jersey calf. They're the less likely to be heat stressed.
Brad: Yes. That is the correct answer. Yes. Joe is jumping up. He probably can jump from Scotland back to the US with that. Joe and I will tell you that Jersey is the answer.
Bethany: Wow. Sweet. [chuckles]
Brad: Yes. I grew up with Jerseys, and Joe loves Jerseys. Sorry, Emily, we didn't say Holstein today. You will have to find your own guest that will say, Holstein.
Bethany: That's just the obvious answer, right? That's too easy.
Brad: Exactly. Exactly. Exactly, but we will take Holstein people too. Anyway, so I want Bethany to introduce yourself. Bethany currently works as a Calf and Heifer Technical Specialist with Vita Plus. Vita Plus is a nutrition company based out of Madison, Wisconsin. Tell us a little bit about your background, Bethany, where you're from and how you got to Vita Plus.
Bethany: Absolutely. It's definitely more of a meandering path than I thought it would be, but here we are. I grew up on a 500-cow dairy herd, Holstein, in Northwestern Wisconsin. That's where I currently reside again, but I went to school at UW-Madison for my undergrad. During that time, my undergrad advisor had a PhD student who had just started at Florida, and she's like, "Well, you could go down there and work for her," when I was thinking about grad school. I was like, "There's no cows in Florida. I'm not interested," but I went down and I toured, and I fell in love with some of the research that was going on down there. As you can probably guess by now, it was a lot of the heat stress work in dry cows and calves. I started a lot of that research down there.
I'd say the emphasis of my dissertation is looking at mammary development and general physiological responses of calves that are heat stressed either in utero or after birth in the preweaning period, so did a lot of that work in Florida. Then about halfway through the PhD, my advisor, Dr. Jimena Laporta, took a position back at UW-Madison; so returned back near the homeland and finished up my PhD, and started with Vita Plus just this last year. My role now is a combination of supporting our customers in their management and nutrition needs, but also having great conversations like this and educating people about some of the science behind managing dairy calves in the most optimal way.
Brad: Definitely you will get heat stress conditions in Florida.
Bethany: Yes, I had a pretty easy time getting what I needed down there. [chuckles]
Brad: Yes, Florida has a different way of dairying. Definitely, sometimes farms just don't breed cows during the summer in Florida. It's so hot and miserable for the cows that they just stop breeding because nothing gets pregnant.
Bethany: Yes, there's a lot of seasonality there, and honestly, a fair amount of shipping calves after birth. If they're born in the summer months, they'll send them to a calf ranch somewhere else just because it's just such a heat load for them.
Brad: Yes, so if you want to study heat stress, definitely Florida is the place to be.
Bethany: Yes.
Brad: The reason why I asked Bethany to be on here today was I saw a post she had on the internet, or maybe it was Instagram, that said there's a lot of talk about heat stress in dairy cows. It's one of the things that we all think about, especially when we get into summer, with how to cool cows. I've worked in California. Cows are hot during the summertime, there are sprinklers, you name it. In the Midwest, we get heat stress.
One thing that maybe gets forgotten about a little bit is heat stress in dairy calves. We never really think about, "Man, maybe those calves can be heat stressed as well." Why do you have an interest in heat stress in calves? I know you did your PhD work in it, but why should we think about heat stress in calves?
Bethany: That's a great question, and I do think we have to be careful. I think a lot of the times, we see a problem in the dairy space and we start shouting it from the rooftop that everybody has to be concerned about this immediately like it's the most important problem. I think it would be false to say that we should prioritize cooling our calves before our cows. That's unfeasible for a lot of reasons, but like you said, I think sometimes we get so focused on the cows that we forget that calves are mammals too and they have needs just like any other mammal on the farm.
Just to take a step back and talk about what that mammal is. Any mammal has what we call a thermoneutral zone. This is just the zone in which there is no energy needed to maintain a consistent core body temperature. As you can imagine, and I know you see this a lot up North, Dr. Heins, of in the winter, they have a higher thermoneutral zone, so that means that they get colder a lot faster. Consequently, in the summer, it takes them a little longer to get heat stress, but that doesn't mean that it doesn't happen.
When we think about that upper critical limit for calves, that can be anywhere between about 70 degrees Fahrenheit all the way up to 82 degrees Fahrenheit, depending on the climate, talking about Florida versus Wisconsin; depending on the size of the calf, what their nutrient program is, their other health concerns. That's another reason, I think, that we often forget to discuss it is because it's nuanced and complicated, but it does happen. The great news is research from my group, other groups at UW, Florida, across the country, really, have started looking at what happens when calves get heat stressed and what we can do about it.
Brad: Is it more difficult to determine if a calf is heat stressed compared to a cow? If we go out to maybe a pen of calves or some hutches, is it difficult to tell whether they're stressed or not, or what might be some of those signs that we see visually in the calves that are heat stressed?
Bethany: Yes, that's a great question. I think one of the number one indicators we use with cows is the Bulk Tank Report, Looking at either herd lactation levels, or if you have milk meters, individual lactation levels. Of course, we're not going to have that with calves. The only productive measure we have with calves is growth. One, oftentimes people aren't measuring growth on a consistent basis in their calves. Two, it honestly takes a pretty severe level of heat stress to see a growth difference.
That being said, there's some initial markers of heat stress that we can use for calves. We call these thermoregulatory responses. The three most common are respiration rate, skin temperature, and rectal temperature. The first two, respiration rate and skin temperature, are quick indicators. They're not going to necessarily reflect the actual core body temperature, really the only way we can do that is by taking a rectum temperature with a thermometer, but they're a really great initial indicator, especially if you want to minimally disturb your calves.
When we're looking at respiration rates, based on a couple of research papers that we have both at the University of Florida and Wisconsin, here in the Midwest, you'd be targeting anywhere between about 40 to 60 breaths per minute as your benchmark for the initial signs of what we call thermal discomfort, which is like a predisposition to heat stress about to happen. Easiest way to do this, just find a calf laying down and measure her flank movements just above her leg and just up and down. I usually do for either 15 seconds multiply it by 4, or 30 seconds multiply it by 2, and just use that as your benchmark. You should say about probably 12 or so calves in your hutch lineup or in your group pen. That gives you a good initial starting point.
Brad: That's relatively easy for farmers or any employee on the dairy to go and just watch a few calves to see if they are heat stressed. I think that's an excellent point is just to watch some calves and their breathing, and you'll be able to tell whether they're heat stressed. Obviously, some you can tell are really heat stressed if they're breathing really hard. That's probably a pretty good indicator that they are stressed. Sometimes it's like, well, are they or aren't they stressed?
Bethany: It's interesting you bring that up because many of you are probably familiar with Dr. Jennifer Van Os. She does a lot of really great work on the cow side and calf. When we talk about monitoring heat stress in cows, she says that if we get to the panting level, it's too late, we could have intervened a lot earlier. I would say the exact same for calves, right?
Brad: Sure.
Bethany: If they're physically panting, we know that we could have taken steps a few steps back in order to prevent that from happening. Panting, in case you want a benchmark for that, is usually about 120 breaths per minute, or if you see an open mouth or any sort of salivation, that I would be saying, "Man, I wonder what we could have been doing a couple days ago."
Brad: Well, that's good to know because I've seen that in some of our calves before is that they're panting or you can really tell they're breathing. It's good to know that it's probably too late, and we should have been looking at this a few days before. I think that's one thing that we always-- When we're on-farm, everything is so busy, there's so many things going on, and we forget about looking at some of those aspects, but like you said, do this on a few calves and just to see- as a benchmark to see where they're at and see what's happening.
Bethany: A couple tidbits I heard in there too that I think, one, nobody's perfect when it comes to all of this and there shouldn't be any shame associated with, "Oh, my calves are really hot." The good news is we can do something about it at any stage of the game. Second, that's a great place to be bringing in an expert on your team. If you work with a calf consultant or even your nutritionist or veterinarian, just ask them, "Hey, the next time you walk calves, could you just count some respiration rates for me quick," or really, if you want a really in-depth assessment, grab your rectal temperature and see where that's at.
Brad: Is respiration the first go-to, and then if we see some signs of increased respiration, then do we go to rectal temperatures and check that out?
Bethany: I think it depends on the time availability you have and how in-depth of an assessment you want to make. Obviously, like I said before, your gold standard for if heat stress is actually occurring would be to go and look at what's happening in the core of the calf. Couple of issues we run into. I just got this question the other day and it was such a good one of, how do we distinguish a fever and a respiratory incidence from heat stress? It can be a challenge because they have a lot of the same symptoms, and quite honestly, they can happen concurrently. There is an increase in respiratory incidents in the summer months.
A couple of things I would be looking for there is looking for additional signs on top of heat stress signs if you think there might be respiratory, so droopy ears, coughing, goopy eyes, tilted head, to investigate more down the respiratory route. That's why I sometimes get a little hesitant to suggest taking rectal temperatures because sometimes that can just lead to unnecessary antibiotic treatments if it is solely heat stress. Benchmarks for that, I'd say anything over 104 is pretty severe heat stress. Starting at about 102, 103 Fahrenheit is when some vets and some scientists would say heat stress is starting to be something to think about.
Brad: That's interesting. I've had that debate with my students before about rectal temperatures are good, I think they can help try and figure some things out, but sometimes it was like, we're seeing high rectal temperatures in calves during the summer and it's like, well, okay, is it just hot and is it heat stressed or is there some sort of disease going on, whether it's respiratory or something else going on?
I've seen calves here at our research center that we've been working with over the summertime have rectal temperatures at 104, and it's like, okay, what's going on? Is this calf sick? Some people might go, "Oh, well, it's sick. It coughed a little bit." The other aspect you have to look at, okay, maybe it's 100 degrees out on a hot day and it's like, oh, well, yes, maybe it is stressed.
You go on-farm. What are things that you bring with, and how do you measure temperature and calf respiration rate on farms? What that might look like?
Bethany: It's actually pretty simple. The two things I look at, I mentioned that one is respiration rate, the other is environmental temperature. You can simply use your weather app to get a broad idea, otherwise there's a lot of really great temperature monitoring tools out there now. Kestrel temperature DROPs are one that I'm seeing a lot of people use. The Van Os lab has a great resource on the protocols for that. Basically, you just turn it on and it continuously monitors temperature for however long you want.
I am often going to be putting one inside of whatever calf housing there is, especially if it's a hutch, since those can start to be like little mini ovens in the summer, and then one on the outside. I think that does a really great job of showing that what we are experiencing outside the hutch and what we're seeing on our thermometer for our external weather might not be what the calf is getting when they're inside the hutch.
Then the last thing that I'm looking at is airspeed. Ventilation, as we know, is incredibly important for calves. A lot of the times when we discuss ventilation, though, it's from an air quality perspective. I think we have a lot of room to improve on maximizing ventilation for heat abatement purposes. I'm bringing an anemometer, which is basically an airspeed measure, on-farm to determine the average airspeed at the calf level in different housing situations.
Research there, we're still trying to determine what kind of targets we're looking for in the summer. We look passive ventilation, so if you just open your hutch door or if you have a naturally ventilated barn, that's usually about 0.33 miles per hour, and this seems to be adequate in a lot of situations. Whereas active ventilation from fans is usually anywhere between 1.7 to 2.2, that's in meters per second. I think it's up to 3 or so miles per hour. We have some work there to determine what is necessary for calves, especially in different environments.
Brad: You'd mentioned calf hutches or single-based systems. I think there's always the misconception out there that if it's hot out in the summer here, say, in the Midwest, but the calves are in individual hutches, well, they must not be stressed because they can go inside and be in a hutch. Yes, maybe it helps a little bit, or are the hutches- is that an oven as well in creating more heat stress for that calf?
Bethany: I really challenge people to think about why hutches were invented and why we like them so much. We like hutches so much because they do a great job in the winter of keeping calves warm. What does that mean in the summer? They're going to keep calves warm. They're just a really small space. The plastic material, especially the white, it does help, but it's still a really enclosed space. I've seen anywhere between just maybe a 1 to 2 degrees Celsius increase up to like a 13 degrees Celsius increase inside these hutches.
Brad: Wow.
Bethany: Which convert to Fahrenheit on your own because I'm not very good at that, but [chuckles] it can be a lot warmer in there.
Brad: Yes.
Bethany: Another misconception, I think, is that the hutch provides shade, which it technically does, it has that protection from solar radiation, but just that increase in the microclimate, I think outweighs any benefit there. We talk a lot about providing shade structures, either over the hutch itself or over the wire paneling in front. You see a lot in Florida, like just open wire paneling and then shade structures over the top of that to prevent some of that oven capacity.
Brad: What about water? If they're stressed, will they be trying to consume more water in a hutch system or will they not be doing that as well?
Bethany: I would say from a science perspective, we actually don't know if they do, but I would say anecdotally, and I'm pretty sure any farmer would say anecdotally that, yes. Water is incredibly important at any stage of life in any season, but especially in the summer, as we talk about both respiration and sweating. Basically, they work to cool the body by moving moisture to the skin surface. That means there's less moisture available for the calf to do her general physiological functions, so water is very important.
We want to drink water in the summer, so do our calves. If we're not providing that, especially if there's additional scours events going on, we're just really setting calves up for a rough time. I do say, actually, you can still provide warm water in the summer. Calves seem to just really like that warmth for that initial interest. I'm usually after that first bucket of warm water, maybe two, then I'm topping off with cold and leaving cold for the rest of the day.
Brad: Sure. As we're coming into heat stress season here in the Midwest, we've had some hot days already. It's been almost 100 degrees Fahrenheit here, at least in Western Minnesota. I'm sure in other parts of Minnesota and Wisconsin, it has been. What are some things that we should do to try and reduce heat stress of calves, and what can we do for abatement strategies if farmers and people are looking for ways to reduce stress in their calves?
Bethany: Yes. I think the first thing, as we talked about, is just assess your current situation, see what your hutch structures looks like, what your barn is like. Are the curtains open? Are your fans working? The next would be to maximize ventilation in different avenues. The extent to which you do that, I would say depends on what your calves tell you, what those respiration rates tell you.
There is a nice paper by Moore in 2012 that looked at the science behind propping up hutches to get some additional ventilation and that improved both airspeeds, but also air gas levels. That's great. Win-win on both of those. A few other things you can do is simply just open those hutch doors that come with your calf hutch. Make sure that the rear is open. You can open the side green door. In a barn setting, there's a lot of different new ventilation tubes on the market that have summer and winter settings. That's something to look at. Adding a couple of basket fans or even low-speed, high-volume fans up top, like ceiling fan-type things, another great option.
I do think there's a lot of different avenues to explore on a variety of budgets that you might have for your heat abatement strategy. Shade would be the last one. Especially if you have pastured animals, doing some sort of shade core structure is very economical. Just make sure that you're providing enough square footage to allow every heifer, every calf to have the opportunity to enjoy it.
Brad: Yes, shade is important, especially for us here at our research center. We have had calves raised on cows in the past and have had them on pasture, and they're stressed, and you'll find them in the shade, whether it's trees or underneath some sort of structure.
Bethany: Yes. As I'm driving through the countryside, that's always my key indicator if it's hot outside, if I see, especially just your smaller beef operations, all those black cows are under the shade trees on the side of the pen. That, certainly, it's an option if that is what's available to you. I think your group is doing something really interesting too with using the solar panels as shade. I think we often talk about that solar panel area as being dead area, but it certainly is not. It can have a lot of benefit.
Brad: Just trying to reduce heat stress in all animals is important because you see-- reduced milk production, obviously, in dairy cows is really easy to see, but some of those indicators in calves are not as easy to see, at least the long-term effects of that.
Bethany: Exactly. I would say, on that note, that's often a question we get about, "Okay. Well, if this happens in my young calves, what does it mean long-term?" I'm sure many of you have heard the discussion around in-utero heat stress and its multi-generational impact on lactation performance. That just comes down to some of the in-utero programming of the mammary gland and metabolic structure and things like that.
We do think that there could be some consequences on this postnatal preweaning heat stress on future performance, especially if it continues up until the post-weaning breeding age. Which of course happens more in Florida than it does here. Our heat stress window is a little shorter, but we are starting to think-- and my former advisor now, Jimena Laporta, she'll be looking at some of that with different feeding planes and long-term success of these heat stressed calves.
Brad: Yes, that's fascinating stuff into the future and seeing how does- even when the calf is being in utero and the cow is heat stressed, how does that affect the calf and its growth and subsequent production in the future? That's one thing that we definitely don't think about is when we have this pregnant cow or heifer, we don't ever think-- we just want to get that calf out and have a live calf. We don't necessarily think two, three years down the road what the heat stress happening now can affect that calf in future life.
That's fascinating. I think, yes, we're on the cusp of trying to figure that out, and I'm glad to hear your advisor is working on that stuff because it's certainly needed.
Bethany: Yes. I think there's just always more to come on that in terms of, can we rescue that phenotype once it's been perturbed? How much cooling is needed for our dry cows? I think that's going to depend on region. Does it need to be the whole dry period? Short answer is yes. There's a lot of mini questions with that, that if anybody ever wants to dive into that aspect, either Dr. Geoff Dahl, Dr. Jimena Laporta, or myself, feel free to reach out to us. I think we can help you discern what might be the best path for your dry cows.
Brad: Those are actually a lot of the notes that I had. Any other additional points you want to make?
Bethany: I guess the last thing I would say is from a general management perspective, I often get questions about how other aspects of management need to change in the summer. I'd say you can keep things pretty status quo as long as you're continuing to offer fresh, warm, and then cool water. Milk replacers or whole milks can stay at the same plane of nutrition, as far as we know for now. Like I said, there should be research coming on that, I hope.
Then I would say the only thing that I would maybe keep an eye on or change is really being aggressive with your scours protocols and electrolyte feeding. It's going to provide a double benefit in the summer of getting calves through scours, and also providing the electrolytes lost during sweating in heat stress. Blanket electrolytes are something that a lot of Florida herds offer in the summer, and I really encourage it up here in the Midwest too.
Brad: I've never heard of that. That's something I learned today that they would provide electrolytes during periods of heat stress. Is the idea is just to keep them hydrated?
Bethany: Yes, and to encourage water intake. A sweet-tasting water is maybe a little more interesting to consume. A couple of things I'll say on that is when we think about electrolytes, there are sodium acetate, sodium citrate, and sodium bicarbonate-based electrolytes. Sodium bicarb is one that I would use for a blanket. It's usually going to be cheaper. It's not going to disrupt the blood acid balance as much, so you can do it longer for all calves. Your sodium acetates and your sodium citrates are ones that are a little more heavy-hitting, so of course that comes with the price tag. I would be saving that for my, I have a scours calf, or I have a calf who's just not looking great.
Brad: Feed your calves water, keep them on the same plane in nutrition, and maybe provide some extra benefits through electrolytes if they're in some heat stress situations, and you should have happy, healthy calves, right?
Bethany: Yes, you should get calves through just fine. Like I said at the beginning, let's not make mountains out of molehills. This is something we can certainly work through, but it is definitely something to keep in mind as we hit really high temperatures this summer. If anybody ever has any questions, you can feel free to reach out to me at bdado-senn@vitaplus.com. I also really enjoy posting on LinkedIn, and I'm @lactationsennsation on Instagram, so [chuckles] lots of different ways you can learn about mammary physiology and heat stress.
Brad: Yes, definitely, give Bethany a follow on Instagram or LinkedIn. That's where I learned about your ideas on heat stress of calves. I'm glad that you were able to join us today and give us a little insight on that.
Bethany: Thanks for letting me share about my passions.
Brad: If you have any further questions, comments or scathing rebuttals, you can contact Joe Armstrong and Emily Krekelberg. Do not contact Brad. You can contact them at themoosroom@umn.edu, and you can find us on Twitter @UMNmoosroom. Thank you for joining us. Raise great calves this summer.
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