Guests: Dr. Geoff Dahl, University of Florida & Dr. Jimena Laporta, University of Wisconsin-Madison We are back at the Real Science Exchange and invite you to pull up a chair and join us to discuss the effects of heat stress on late gestation cows. Tonight’s guests, who have worked together on research in this area, Dr. Geoff Dahl with the University of Florida and Dr. Jimena Laporta with the University of Wisconsin-Madison, join Scott Sorrell and Dr. Clay Zimmerman.
Guests:
Dr. Geoff Dahl, University of Florida
Dr. Jimena Laporta, University of Wisconsin-Madison
We are back at the Real Science Exchange and invite you to pull up a chair and join us to discuss the effects of heat stress on late gestation cows. Tonight’s guests, who have worked together on research in this area, Dr. Geoff Dahl with the University of Florida and Dr. Jimena Laporta with the University of Wisconsin-Madison, join Scott Sorrell and Dr. Clay Zimmerman.
Dr. Dahl kicks off the discussion by level setting with the idea that cows have a thermal comfort zone and that it’s not just temperature but also humidity that can stress a cow. 4:44
To get a more accurate stress reading, Dr. Laporta and Dr. Dahl’s research has focused on measuring stress and environmental indicators without getting in contact with the animal. 8:40
Dr. Laporta discusses the stress can continue into future lactation periods of both the dam and the offspring. 16:45
Both researchers highlight their opinion on cow longevity in the herd and how stress can change the length of the cows’ time in the herd. 22:48
While the Florida humidity heightens the stress Dr. Dahl sees in Florida; both researchers highlighted they see seasonal effects on cows everywhere. If lactating cows are under stress for even a week, Dr. Laporta discusses the short-term event will have a long-term impact on the cow. 35:54
Heat stress can also cause acceleration of the maturation process for gestation timing. Dr. Dahl discusses the calf is signaling it is ready to be born based on the increase in the cows’ internal temperature. 45:09
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Scott Sorrell (00:07):
Evening everyone. And welcome to the Real Science Exchange. The pub cast where leading scientists and industry professionals meet over a few drinks to discuss the latest ideas and trends in animal nutrition though. Though the weather recently has been cool in many parts of the country, the heat of the summer will soon be here. And tonight we'll be discussing all the different ways heat stress impacts not only the cow, but also the calf she's carrying. Hi, I'm Scott Sorrell one of your hosts for the Real Science Exchange. I see that Dr. Geoff Dahl has joined us at the pub tonight. This week's conversation started with webinar presentation just a few weeks ago. Dr. Dahl, from the University of Florida, was part of the real science lecture series on May 4th. If you'd like to watch the presentation, just go to balchemanh.com/realscience and scroll down to the past webinar list. Welcome to the exchange, Geoff what's in your glass tonight.
Dr. Geoff Dahl (01:01):
Thanks Scott. And really a pleasure to be here. So I am drinking a, a Uruguayan tannat in honor of my guest who is originally from Uruguay. It's a nice red. It's a fairly bold, but it has a nice smooth finish. So that's probably a good description even of my guest. Excellent.
Scott Sorrell (01:21):
So you mentioned your guest- would you mind introducing who that is?
Dr. Geoff Dahl (01:24):
Sure. this is Dr. Jimena Laporta, who is an assistant professor in the Department of Animal and Dairy Science at the University of Wisconsin- Madison. And Jimena and I have worked together. She was previously on the faculty here at the University of Florida, and we have done quite a bit of work together in the area of heat, stress of the dry cow, and also more recently the effects on the calf that that animal is carrying.
Scott Sorrell (01:55):
Excellent. Jimena, welcome to the Real Science Exchange. What are you drinking tonight first? And then can you tell us a story about your, your time working with Geoff?
Dr. Jimena Laporta (02:06):
I am drinking- thank you for the invitation first- and I am drinking an old fashioned and a real one. So thank you, Stephanie, for arranging that! A story about Geoff- I don't know where to start. I have so many, but they're all great. It’s been a real pleasure working with him. I knew Geoff just being in lactation biology's, you know, working the photo period and everything. In 2014, he actually hired me at the University of Florida. So we started working together in this research and it's been a real pleasure. We have shared, you know, we shared a lab, we share post doc students and it's been really fun. I think our most interesting aspect is that we get along really well. We have kind of the same sense of humor in a way that not a lot of people get. We also have fun. So that's, that's really important.
Scott Sorrell (03:09):
Well, excellent. Well, glad to have you here tonight. And I'll say the old fashioned seems to be the popular order here, usually here at the Real Science Exchange, but Dr. Zimmerman, our trusty co-host is back with us. Clay, now that summer's almost here you having anything different in your glass?
Dr. Clay Zimmerman (00:03:28)
I actually am. I have a hard cider, but in honor of the warm weather, it's a watermelon cider. If this bottle is empty by the end you'll know what was good.
Scott Sorrell (00:03:41)
Excellent. I'm expecting maybe a milkshake. One of these days. Does, does angry orchard make a milkshake?
Dr. Clay Zimmerman (00:03:49)
I don't know. Scott, what are you drinking tonight?
Scott Sorrell (00:03:51)
Wow. Thanks for asking clay. I've got something very unique. I I've I've, I've dispensed with the bourbon this time. I'm drinking a red beer in honor of my brother, Rex, who was working at the BearTooth ranch in Montana and went out to visit him one time. And he introduced me to to red beer. This, this particular one is made by bud lightens called chilada. So it's very interesting. Would recommend it. If you ever get a chance, it's basically beer mixed with a tomato juice, believe it or not. So it's quite tasty and then a bit summery. So there you go.
Dr. Jimena (04:25):
I do recommend the Uruguayan tannat that Geoff is having. It’s really, really, good.
Scott Sorrell (04:28):
That's a good one? We'll have to, we'll have to take that down then. Excellent. We'll put it in the show notes so everybody can get it. So Geoff, let's get started by defining heat stress. What point does it start impacting the animal's health and performance?
Dr. Geoff Dahl (04:44):
I mean, cows, just like every other animal has a sort of a thermal comfort zone, right? That's a range of temperatures where they're comfortable and if you go too low, they're going to be cold stress. If you get above that, they're going to be heat stressed. Typically, we don't use absolute temperature as an indicator because there are other factors that are going to influence the ability of an environment to cause heat stress, particularly humidity. And I bring that up just because I live in a hot and humid environment. And in a matter of fact, in the summer in Florida, it won't get as hot as it might in a lot of the continental U.S. You get much hotter than we do an absolute temperature, but the killer for us is the humidity. And so when you combine the temperature and the humidity, what has evolved as a temperature humidity index. And typically for lactating cows, we tend to think that as about 68, and if you move above a temperature humidity index of a 68,
(05:44):
those cows are going to start to experience heat stress. In dry cows, we had been using that number, but we've got some new information that suggests that it might be a little higher than that, which makes sense, because those are going to be consuming less feed there's less heat of nutrient metabolism. They're just producing less heat. So they've, they've got an easier time, to a certain extent, with their environment. But we have to always remember that, you know, dry cows do get heat stressed and they will do things like reduce their intake and they will have some pretty profound negative impacts on their next lactation, but also on the calf.
Dr. Jimena (06:26):
So that CHI that Geoff was talking a lot for dry cows it's 77, according to our calculations. So quite different from lactating cows. We've also done some work in calves, and those breaking points are even lower. They're about 66, 67 for respiration rate and rectal temperature for the calves. So that's some interesting work that we have been doing in Florida. So very interesting.
Dr. Geoff Dahl (06:59):
In terms of when they're going to be heat stressed, you can take a temperature. You can do rectal temperatures. We have sort of looked at respiration rate as our indicator. And across a number of studies now, and this is with dry cows, if they get above 61 for a respiration rate, they're heat stressed. And the more that increases, the more severe the heat stress is that those animals are under, but it's actually not a, it's not a real high respiration rate. You can certainly walk into a lot of barns and see cows at that respiration rate. So they will get heat stressed at a fairly low sort of temperature and humidity.
Scott Sorrell (07:41):
So how good of a, an indicator is rectal temperature? I recall that you, you, you mentioned that in some of your research, can they be heat stressed and still not showing elevation and rectal temps?
Dr. Geoff Dahl (07:53):
Usually there'll be some- it's whether you can discriminate it or not. And, you know, that's one of the reasons why, at least from, from my perspective on the farm, when I'm just walking around pens, I think I'd rather use something like respiration rate because I can do it without bothering the cows. And we know that if we get them up moving around, even the tamest of cows, when we go to take a rectal temperature, they're going to jump up and move around and that can sort of influence their, their temperature as well. So I just like to be able to observe a group of cows and rather than taking a rectal temperature, use that respiration rate to give me an indication of how hot they might be.
Dr. Jimena (08:40):
So that’s kind of the, the type of work that we have been doing recently to try to estimate. So the heat stress indicators, environmental indicators, and animal based indicators that don't require, you know, getting in contact with the animal and trying to figure out a way, an easy way and more precisely determined, express without getting in contact with the animal. So that that's very helpful for, from a producer standpoint. So that's kind of our objective with those studies.
Dr. Geoff Dahl (09:15):
Yeah. We haven't even looked at it in cows out on pasture. And it's interesting, when we have cows in the barn versus out on pasture at night in the summer we do see some recovery in those animals, even at a high THI, but the sort of negative of them being without shade during the day, and the increase then you see in temperature then really overwhelms, I think, any benefit that we get from them being outside and, and not allowed to have access to active cooling.
Dr. Jimena (09:56):
Yeah. I think we were served like respiration rates of up to 130 I've known, so that's, that's pretty tough on pasture.
Scott Sorrell (10:07):
So now, as I recall, Geoff, I was looking at your presentation again today in preparation for the podcast and, and for the listeners out there. Even if you listen to the webinar already, I'd encourage you to go back and listen to it again. Because I learned an awful lot the second time around. There's just some missing nuggets in there that I miss. So I'd recommend going back and listening to that again, but you had broken your presentation down into three primary parts. One is the impact on the cow, the impact on the calf, and then you kind of dove into the economics, let's start with the cow. What are some of the things the significant things that you're seeing that heat stress does to the performance of the gestating cow?
Dr. Geoff Dahl (10:56):
Yup. So when the animals are actually in the dry period, you know, we don't see a whole lot from the sort of metabolic perspective. So they will have a drop in their intake. But if we look at, for example, insulin concentrations, glucose, NIFA's- we don't see a whole lot going on there in terms of the comparison to lactating cows, where we do see some of those, those change. And, and other folks have, have worked on that quite extensively . Where we do see significant impacts is on mammary growth. And so, you know, the dry period is a time when we're seeing sort of loss of senescent tissue in that mammary gland. And we're seeing regrowth and preparation for that next lactation. And our observation is that all of those processes are going to be favored by cows being cooled versus animals being heat stressed.
11:59):
So when they're heat stressed, they're going to have lower proliferation of the mammary gland, of the mammary tissue. So you're setting yourself up for less capacity for milk production in that next lactation. There's not an effect on the loss of cells, at least as we move into the dry period, but it does seem like there may be some subtle effects early on and allowing for sort of clearance of those older cells, that then makes way for those newer cells to, to grow in and develop for that next lactation. And that persists then into the next lactation, that capacity for a greater milk yield. We see that at more of the tissue level, when we look at alveolar number, there's going to be an increase again, indicating an increase in capacity for milk production in those cows that were cool versus those cows that were heat stressed.
Dr. Geoff Dahl (12:54):
And the other area that's impacted is a immune function. So we will see during the, during the dry period when cows are heat stressed, that they have a reduced ability to proliferate white blood cells. They've got a reduced ability to respond to. When we did it, it was just an innocuous antigen. It was essentially egg white that we vaccinated cows with just to get an idea of how they mount an immune response. And we observed that the cows that were heat stressed had a lower response. And that is important obviously because we do a lot of vaccinating in dry cows. And so if that heat stress is limiting their ability to respond, then we may be setting them up for bigger problems as they move into that next lactation. A lot of the effects that we see though are just resultant of what was happening during the dry period, and they actually show up in that next lactation and the cows that were heat stressed typically are going to produce 8-10 pounds a day, less than the cows that were cool, and that persists for the entire lactation when we followed it out.
(14:08):
It also doesn't matter, it seems, when we heat stress the cows. When we've done it early, we've done it late in the dry period. They all seem to have the same sort of response that diminished capacity for not production the next lactation.
Dr. Clay Zimmerman (14:25):
So, Geoff, I've always been surprised when you ran the study, looking at when to apply the cooling during the dry period... it has to be present the whole dry period. Can you, can you maybe explain that again?
Dr. Geoff Dahl (14:42):
Sure. So the, the process of, of sort of that, that tissue growth at memory growth you know, it's always ongoing and when we stop essentially lactation, when we dry the cows off that's, as I interpreted a signal to them to go through this sort of regenerative process, and it's not just that, oh, a bunch of cells die off and then new cells appear. It's more of, we think a sequential process where we're going to get clearance of some of those senescent cells early in the dry period, which then sort of sets the foundation for increased proliferation as the dry period advances. And then eventually we're going to get them to be sort of stimulated when they go through lactogenesis to produce milk. And so when cows are heat stressed, there's going to be effects on that early response. So during involution, exactly. And so that's going to be diminished with heat stress. It's not, as you can think of it as, you know, they don't have as aggressive of period of involution, but that then delays that proliferation later down the road. And I think that's why we see the responses that we did where, if we don't have both of those in play, you won't realize the sort of positive in that next lactation.
Dr. Jimena (16:08):
When you look in the next, next lactation, they indeed have, as Geoff mentioned, less alveoli, which is the secretary unit of the mammary gland. And those arlveoli, I have less secretary cells, so they just produce less milk. They have less inphetic capacity. So you're setting off that cow for a bad lactation.
Scott Sorrell (16:31):
So Dr. Laporta can you expand on that? Are they able to regrow that the, the, the alveoli or the epithelial tissue for subsequent lactations or will that impact them for future lactation? Do we know yet?
Dr. Jimena (16:45):
So for the, for the next lactation, after the, the stress, during the dry period, they are not able, we do not know in subsequent lactations of the, of the dam. But we do know that in the offspring, it affects for multiple lactations, but for the dam under heat stress, during the dry period, we do know that the first lactation is impacted, but we haven't been able to test multiple lactations. We tried, but we, we just don't don't have that data,
Dr. Geoff Dahl (17:19):
But we've got a little bit of a idea, don't you think?
Dr. Jimena (17:24):
Yes. So te first three weeks of the second lactation we see still the detriments, but we, we just don't have enough cows to the second lactation of that dam will be impacted, but because cows are old by then and they are leaving the herd,
Dr. Geoff Dahl (17:43):
That's always our problem with our sort of extended sorts of studies where we're trying to track cows through multiple lactations, right? Because I average cows lasts three lactation. So we want to get to that next lactation variety, two thirds of the way through her productive time in the herd.
Dr. Jimena (18:01):
And we, most of the times with new, more chipper cows. So then by their second lactation, the second..theyre essentially all the way through.
Scott Sorrell (18:10):
So what impacts does that late gestation heat stress have on that calf?
Dr. Geoff Dahl (18:16):
Well, I'll start, but I'm going to turn it over to Jimena pretty quickly, but, you know, first thing that we observed are all of the typical expected effects on the calf with heat stress, because plenty of people have shown that cows calve earlier when they're heat stressed- a few days earlier. The calves are typically smaller about birth weight. We do know that that extends through weaning. It extends through a year of life in terms of the lower weight in those animals that were from heat stress, Dan. So there are persistent effects on growth. We observed that in, in a sort of early summary study that the calves that were born to the heat stress dams have poor survival in the herd, and they make less milk in their first lactation when they've been heat stressed in utero. So everything else being equal from the time they hit the ground until the time they calve for the first time, two years later, those animals that experience heat stress in utero are going to have about a, again, an eight to 10 pound a day hit from a milk production standpoint versus her herd mate whose dam was cooled in the next pan over.
Dr. Geoff Dahl (19:29):
And so there's, there's a lot to that. And we're, we're starting to look at that. And Jimena actually has, now we've completed a study that, that was looking more at the sort of developmental aspects of that, that I'm going to let her explain.
Dr. Jimena (19:47):
Yeah. So to add to what Geoff was saying we just looked at the mammary glands of those in utero heat stress heifers versus a utero cooled calves. And we saw that their mammary glands were smaller. We, we looked at that as a percentage of body weight and the gross weight of the glands. They are shorter, they are smaller, they have shorter teats and that's not only the growth weights. Also, the parenchyma tissue is fraying, and that's not only true for the birth mammary gland, but also at the weaning. So eight weeks after, you still see that lag in growth of the mammary gland and not only the mammary gland, but also certain other tissues such as immune-related tissues, stress-related tissues, the adrenal gland, and other tissues as well. And that's some confirmed in some of the earlier work that just Geoff has done showing impacts in immune function as well. And when we look at the heifers during their first lactations, we also see detriments in mammary growth. So they have smaller alveoli and less secretory cells as well. So whatever's happening in utero is permanent, apparently not for the first lactation, but also for the second and third lactation of that daughter. So it's a pretty impactful.
Dr. Geoff Dahl (21:24):
Because I mean, your summary clearly shows that, right, that the daughter then in her second lactation makes less milk if she was heat stressed. In her third lactation, she makes less milk. So it's the gift that keeps on taking rather than giving.
Dr. Jimena (21:38):
Yeah. And if we think about it, this is just a 46, that's a, what we target during the dry period, 46 days off in utero heat stress. So whatever's happening in utero, it's changing the morphology and the molecular signature of that mammary gland that will not allow her to produce milk as she should, her genetic potential would allow her for. And that remains with her for three, at least three lactations that will we have tracked for.
Dr. Geoff Dahl (22:11):
So essentially for her time in the herd, if we go by sort of average length of time, and, you know, if you look at survival in the herd, those heifers do not last as long. It's for a variety of reasons, but they don't last as long, which is also telling, right. That's sort of the, the, the...
Dr. Jimena (22:32):
I think that's, that's one of the biggest impacts. I think that you're raising that heifer and she's not even making it to the first lactation..and if she makes it, she's going to produce less milk. So it's an animal that you probably don't want in your herd.
Dr. Geoff Dahl (22:48):
Well, I think about all of the emphasis lately on longevity and how long cows should last in the herd, right? There are certain management things, sure. There's, there's genetic issues as well, but there are certain management interventions that we can make that will actually extend the length of that cow's time in the herd. Very simply by making sure that she's not born to a cow that experienced heat stress during her dry period.
Dr. Jimena (23:21):
So, if you think about this is a multi-generational effect, and this we're talking about 46 days, that you can do something to avoid this effect on the cow, in next lactation. So you don't lose money and on the calf for at least three, four or five years. So it's, it's, to me, it looks like a good investment.
Scott Sorrell (23:47):
As a matter of practice. Would you guys automatically cull calves from cows that were heat stressed? If you have that option?
Dr. Jimena (23:55):
No, I would cool my dry cow instead.
Scott Sorrell (24:01): the
Of course, but maybe if you don't have cooling.
Dr. Geoff Dahl (24:05):
But of course that then leads you to, and, you know, we've talked about that. I've had plenty of questions like that, Scott, and it makes sense, you know, if I'm in a warmer environment, when do I want calves for replacements? The issue there though is particularly, as we get into larger herds, we're trying to keep a fairly steady flow of animals coming through. And so, to say that I don't want the calves that were born as my replacements that were born in August, September, October in a hot environment. You know, you really start to squeeze down your ability to keep a steady stream of cows going into that herd, calving at an appropriate interval, because you're either going to extend them out or you're going to have cows calving at a little bit earlier than you might like. So there is a lot to that. I mean, it's a great practical question, but there's a lot more to it even than, than just I'm going to eliminate those calves from the herd.
Dr. Jimena (25:04):
Yeah. And also what Geoff was pointing out in his seminar. It's not about, you know, it's not an easy fix if you would be able to fit, fix this by feeding a loss from, right? That will be an easy fix. We will keep, and you will take care of that calf, but it's not that easy. There's something intrinsic to that heifer that will not be wiped away that easily. And we actually tried that because that's one question that we often get, you know, can you fix this? Can you revert this? And we try cooling that calf as soon as they hit the ground. And we see that those effects are still there. So we try, we tried to fix it. One, we're going to keep trying, but it looks like, you know, those are permanent effects, multilactational that are, that stay for, for a long time.
Dr. Geoff Dahl (26:03):
That could have been your funny story, Jimena. You could have told them about when you, when you propose that study and you asked what I think will happen, and I said no, that's not, that's not going to happen. It's not good. We're not going to be able to do it. I think that maybe, maybe..a
Dr. Jimena (26:28):
And I kept insisting that hey, we should do it we should do it, but ehh...Let me do it! And that’s how it works..... I’m a little sour, let me tell you. At least I have my drink.
Dr. Clay Zimmerman (26:37):
Geoff, I'm always curious. How did you get started doing research in this area? Looking, looking at cooling the dry cows.
Dr. Geoff Dahl (26:47):
So you might be aware of some of the work that I did previously with lighting and photo period. And we had foundm one of the sort of really interesting observations we made, and I've done a lot of work with dry cows. It seemed like it seemed like a fertile area because no one else was working in it. So I didn't have much competition. So we did a study where we exposed cows during the dry periods to either long days or short days. And by that, I mean, long day, 16 hours of light, 8 hours of darkness, the typical photo period we'd have them on for lactation. And then the cows that were in the short days were on e8 hours of light, 16 hours of darkness. Really easy to do that in dry cows, because you don't have to milk them twice a day and have light exposure and that type of thing.
(27:33):
And it was pretty shocking when we started summarizing the data from that first experiment, because I had expected the animals that were on long days for a number of reasons to actually do better as they went into that next lactation. But it was, it was crystal clear that the cows that were on short days made more milk from the start of lactation and just like with the heat stress effect, it persists. So we followed that up and looked at various aspects of metabolism, mammary development, that type of thing, and showed that those animals had improved mammory growth. And, you know, the one thing that sort of ties lighting and temperature together is prolactin. So prolactin will increase when animals are on long days, it increases with high temperatures. And while prolactin, you know, when you think about the name, you'd think, oh, well that would be good.
(28:33):
Every hormone has a receptor. And so as that increases, what we find is that prolactin sensitivity decreases, cause the receptor goes down. So, long story short, because the sort of mechanisms I thought would might be similar when I moved to Florida, it was a natural progression to start looking at aspects of heat stress in the dry period, just like we had looked previously at, at lighting. Now what is, I think significantly different first that prolactin effect may not be the sort of driver for some of these responses, even though that's initially how we got into it, but that's how science works, right? We kind of test a hypothesis and just determine whether it's supported or not. And move on to the next study. It doesn't mean that the observations of milk production and other effects are wrong. But we don't see the same effects in the calves.
Dr. Geoff Dahl (29:32):
And part of that is that we don't see the same influences of short days or long days on gestation length and on, I think, placental function. Because where I really think this is all coming back to is the impact that heat stress has on placental function and how effectively that animal manages the heat stress, is to a large extent related to her ability to maintain good placental function. And they just can't do it when they're profoundly heat stressed. And I think that's where we see the effects then on the cow from a mammary growth perspective, but more importantly on the calf. So a long-winded answer, Clay, to your quick question, but that's kind of how it progressed.
Scott Sorrell (30:23):
Yeah. Oh, that was a great question. I'd ask the same question of Dr. Laporta. How did you get started in either a, whether it's a fetal programming or studying heat stress?
Dr. Jimena (30:34):
Yeah. So during my PhD, I was looking at the sort of communication between the mammory gland and the bone and calcium metabolism and storage. When I started at USF (University of Florida), I was well aware of Geoff’s work with photo period. And his work with heat stress, was we're doing that maybe for three, four years by then. And so I got there and we naturally started collaborating, you know, two mammary specialists together. That's what they do, right? So I was fascinated when I got there I think one of your students, she got the very first report showing milk production differences in the daughter. So those in uterus heat-stress heifers. So that was, to me, was fascinating. I was like, I need to go in this direction. I, I want to know, I was curious. I wanted to understand why. And so Geoff and his group, they had a really good model with very consistent phenotypes and I was all in and Geoff, you know, he started collaborating right away and it just led me big into those mammary glands and I asked my own questions, and here we are!
Dr. Geoff Dahl (31:57):
Yeah. Very productive collaboration.
Dr. Jimena (32:02):
Yeah. There's such a large number of questions that we want to answer, that it's a very fertile area that we can both share.
Scott Sorrell (32:12):
Yep. And then that led to the research that you're now doing at University of Wisconsin with the fetal programming?
Dr. Jimena (32:19):
Yeah. Yeah. So actually when I I moved in here, I- and this is another funny story. Geoff said, why don't you take these 40 heifers that we have? And I said, are you crazy? And yes, I have them here. I just pulled them in a truck. And they’re here with me in, in Wisconsin...
Dr. Geoff Dahl (32:42):
Ultimately, ultimately it's all about easiness. I didn't want them, she left- who was going to take care of these, who is going to keep track of them?.. I was going to have to do all that. So why don't you just take, take them with you?
Dr. Jimena (32:56):
So, I have them on I'm raising them. So what I'm trying to do here is the generation, that second generation, so the F2’s, and started looking at mammary development and those F2’s. We know the, the, the daughters, we do have a lot of information on that regard, and I'm going to try to generate the F2 and try to look into those mammary glands and see how these multi-generational effects might translate into the daughters, their granddaughter. The other thing I'm working on is calf cooling, which is an area that we often overlook. And that's something that I have been working on. And it seems to work, you know, like calves can get heat stress too. They are less impacted or in a different way, but we have shown a positive effects of clean calves. So I'm getting creative here in the Midwest and just offering, you know, better ventilation and stuff like that. We don't need to go all the way. I have to remember I'm not in Florida anymore, but, you know, we're, we're kind of trying to mimic the study with it, with the thresholds and trying to understand those breakpoints and looking at the different CHI’s and when those calves get stressed. So that's some work that I'm doing here.
Scott Sorrell (34:23):
So, so how do you, cause long-term heat stress in Wisconsin? Well,
Dr. Jimena (34:29):
I mean, you still have 50 days, 55, 60 days, depending on how you calculate it. Right? Of high temperature humidity index. Let's say two months. The the, the thing is that, you have a lot of cows here? So even if in a short period of time, you can affect or impact a large number of cows. So in Florida, it’s the opposite, I'll say, you have less cows, but you have this long time and so the detriments are huge as well. So yeah, I do think that during those two months it gets pretty hot here. I forgot that it gets hot here as well. But I think, you know, there are some intrinsic differences to what the animals are sensing, of course, a night, it gets cooler that they really don't have any time to cool down, even at night. And so I do think that the effects are, are, are much more pronounced. But yeah, we're, we're going to start comparing those and try to see how relevant heat stress is, here. That's a question that a lot of people ask me, what are you going to do now? It's like, what do you mean- What are you going to do? There is great research in heat stress coming from Canada! It’s not all about geographic location, right?
Dr. Geoff Dahl (35:54):
Yeah, I mean, that's the one thing that you see is consistent and it, isn't just in the U.S.: you go anywhere in the world and you see seasonal effects. These, these play out everywhere. And part of it may be some of the lighting, but I tend to think a lot more of it is probably these impacts of heat stress. And it's only going to get worse around the world as we go forward. So yeah, I, I think there's a lot left to work on.
Dr. Jimena (36:25):
Yeah, and we are working on the late gestation, you know, cow and calf. But there's a lot of folks doing research in lactating, even like a week on these short-term events, they have a huge impact as well. So it doesn't have to be a long-term to have the detrimental effect.
Scott Sorrell (36:52):
That's going to be my next question. I've just kind of curious how, you know, what kind of research is being done there, right? That we're focusing on the last two months, what kind of impact is that having on the calf, the fetus, you know, even, even around the time of conception. I mean, I don't know if we know, or if you guys have looked into that.
Dr. Geoff Dahl (37:10):
Well we haven't, but there are data out there that show that the animals that are heat stressed around the time of conception will have impacts on performance when those animals then are born, after they're born, at calf end two years later the, the issue is for most cows, that's only going to be an issue their first pregnancy. Because any other time that they're conceiving, they're probably going to be cooled if they're a lactating cow. I think that we have probably gotten that message out in most places that we need to cool our, our lactating cows. So really it's a smaller proportion of animals that are potentially going to get heat stressed earlier in gestation, but there are some impacts there as well that people have looked at, at records and your sort of seasonal effects and that type of thing. Those, there are some other studies that have looked at reproductive performance based on whether animals were heat stressed in their first trimester, second trimester, third trimester, and they're consistent with what we observe. It does still seem that the later we heat stress animals, the worse off for that calf. So they can take it a little bit more earlier in development. And you would think that that calf at six to eight weeks before it hits the ground is pretty bulletproof, and she's kind of fully developed and everything is there and now it's just, you know, gain gaining some weight. It’s pretty clear that that's not the case. And so we can have some dramatic impacts on those animals' development and dramatic impacts for that animal's life.
Dr. Jimena (39:02):
So like those early life experiences, like we like naming that now, it's not just during gestation during the first week or month, you know, that you can impact that animal for life. So, they did a transition period off the calf that it's really important, setting them up for a good start. Its not just later. It’s even earlier on.
Scott Sorrell (39:32):
Yeah. I, as I recall, during the presentation, one of the big impacts was on the animal's immune system, both the cow and the calf. Can you expound, one of you on, on the impact on the immune system and, and what you've learned in some of your studies?
Dr. Jimena (39:50):
Go on Geoff, you have done more in the area.
Dr. Geoff Dahl (39:54):
Well, I mean, the first aha was when we just took IGG samples from calves first day of life through weaning or through a month, I guess, a life and saw just dramatic differences between the calves that had been heat stressed and the calves that had come from cool dams. So first thought was, oh, well, we've, we've really messed up colostrogenesis in these heat stress cows, there's, there's an impact there.. Well, not so much. So the effect on colostrogenesis is all one on volume. It's not one on sort of IG content. And typically it's not one enough of one on volume that it would limit how much we have. I mean, you occasionally get those cows, but in general, it's not that much of an effect. But there are certainly other factors in the colostrum that may influence their ability to take up the IG from the claustrum.
(40:55):
And that's what we started working on. Was it an effect on the cow, or was it the calf, or was it an effect on the colostrum itself? And it doesn't appear to be that when we heat stress, the cow, her colostrum is impacted enough to affect the calf, but it looks like that heat stress in utero limits the amount of, or the capacity for, absorption of immunoglobulins. And what it appears is that those calves that are born to heat stress dams, either because they're not as mature, or because it's been accelerated, their gut closure process is already ramped up when they're born. And we've got a study that'll be coming out and JDS communications here in the next month or two that shows that, that the calves that were born to the heat stress dams have a much accelerated rate of gut closure relative to the calves that were born to cooled dams. So the problem with that of course, is it doesn't matter then how much colostrum we put into them there. They just, aren't going to be able to overcome that. And then that leads to some of the sort of downstream impacts on immune status and those animals and their ability to survive in the herd.
Dr. Clay Zimmerman (42:15):
Is there, is there a difference in, in placental weight and these in these at all?
Dr. Geoff Dahl (42:28):
The best answer to that is yes, but it's variable, but I can tell you, we, I think did a reasonable job of placental collection in our study last summer. And we had looked at total weight .And maybe see some differences there, but where we really see it as in the number of cotyledons. And if you go to a presentation at ADSA this summer, you'll be able to see that visually in terms, not just numbers, but the, the size. So it seems like the, the animals that are heat stressed have fewer cotyledons, and they're increased in size. Now, my limited understanding of placental development and placentation is that they kind of start out with the number of cotyledons are going to have kind of early in pregnancy, and then they develop. So either the heat stress is causing those animals to lose cotyledons more rapidly or there's something else at play there, but it does seem like there is less capacity for, and we know this, I mean, from other species, that there's less capacity for nutrient and oxygen transport in those animals that are heat stressed versus the ones that are cooled.
(43:49):
And it makes perfect sense that you might have more of a, a radiative effect in the calves and the cows that are heat stressed versus the animals that are cooled, because they're just trying to deal with getting rid of that heat.
Dr. Jimena (00:44:13)
And it’s almost like they have fused together.
Dr. Geoff Dahl (44:16):
Like the individual cotyledons are bigger as well. And so that may be what it is. It's more of a, it's more of a, a response in order to move heat away from that developing fetus rather than supply nutrients. Obviously it's not one or the other, but if you're thinking about it as a Seesaw, right, we're leaning towards getting rid of heat versus supplying nutrients.
Dr. Jimena (44:38):
And our more recent work now is going to be looking at methylation signatures of those cotyledons and seeing what, what are, what they want to tell us. We're going to dig into those methylations.
Dr. Clay Zimmerman (44:55):
What's, what's causing that the shorter gestation length then in these heat stress. Yeah.
Dr. Geoff Dahl (45:09):
So it's kinda like when I said that the gut closure, is it because she's born a little bit less mature or is it because we're actively sort of moving? It's, it's more of a acceleration of maturation process. And I guess we don't know. But I would say that there's likely an interaction from both the calf side and the dam side of that heat stress. And you're probably seeing some impacts related to maintenance of pregnancy from the dams perspective, but also then the calf is kind of signaling that this needs to be, I'm going to take my chances outside rather than-
Dr. Jimena (00:45:55)
“I’m done, I’m done, I’m trying to get out of here.”
Dr. Geoff Dahl (46:00):
Exactly. I'm pretty sure that the temperature is at a peak and I'm done.
Dr. Jimena (46:06):
And, and the other thing to add there is that the, the, the temperature, the fetal temperature is is pretty much controlled or by the cow. The calves have no ability to control its own temperature. And so it's, it's important to keep that in mind. So if the cow is heat stressed, and this is hard to show in cows we, we know the, from other species goats and sheep, I've actually test that well.
Dr. Geoff Dahl (46:37):
Yeah. And it's one of the, it's one of the features of this sort of programming effect that, to me, it's more of a, a normal range insult than some of the things we can do nutritionally or otherwise, because even a cold stress cow, right? She's going to, and I get that question too: what about cold stress? Will that impact? Well, its not like cows are going to get cold stressed very easily. If we're going to cold stress, a cow that's pregnant, she's probably got other factors that are, you know, she's nutritionally deficient, she's got some other things going on. And so it's more of a pathology rather than this, which is kind of part and parcel and normal physiology and how that animal responds because nutritionally, she's always going to favor that fetus, but from a heat stress perspective, she might favor, she might want to favor them, but there's no way she can, right? The physics just don't allow it. And so she can shunt nutrients towards the fetus at her own disadvantage, but she can't, there's only so much heat she can shunt out of that and get rid of that. And that's all going to be less controllable by the dam.
Scott Sorrell (47:49):
So where do we go from here? What's next for both of you in terms of areas of study, at least related to this, and, and maybe not, maybe you've got some other areas you're looking at as well. Dr. Laporta, where are you headed next?
Dr. Jimena (48:04):
Am very interested in looking at, you know, methylation affects and how heat stress in utero- how we can explain this different phenotypes two, three, four, five years later. I'm very interested in understanding that from a molecular standpoint. And the calf, I'm very interested in that early life period in the calf and how we can set them up for a good start, even if it's in utero or during that pre-weaning period that we often don't think about much. But I think we're now trying, we're understanding that, that here the life is quite important and setting them up or successful lactation. So those are areas that I'm actively working on right now.
Dr. Geoff Dahl (48:59):
So we're going to have a lot of overlap in terms of our areas of interest and sort of the things that, that we do. I too am interested in what's happening in that calf, but sort of mechanistically, particularly from a placental function standpoint, how we can overcome this, are there ways that we can alter effects on the calf? For example, if we see, and we've seen already differences in methylation patterns, which are going to affect gene expression down the road, can we alter that nutritionally or otherwise in the animal, maybe we can't overcome the effect in the cow, but we can certainly overcome some of the impacts on the calf. So some of those sorts of questions in terms of interventions that can allow us to deal with this, because right now we have a very effective way to deal with it, which is cooling the cows, but it takes water.
(49:54):
It takes energy. There's a lot of that. It works extremely well and we know how to do it properly, but you know, there's going to be limitations down the road. And so if we can, in other environments, adjust this and overcome some of these negative impacts, I think that's kind of where we're headed. The other, the other area that we've got an interest in is, again, from some of these samples that we've collected from the calves that were that, that we sacrificed in this last study to look at mammary growth. We also took samples for microbiome analysis. So looking at how we might be affecting those animal’s digestive microbiome in particular, early in life. And then how does that set them up later on for differences in feed efficiency or productivity that might explain some of this. I kinda, I probably have a similar sort of response that I did to the cooling of the calves.
(50:58):
I don't think there's going to be a whole lot of effect, but it's an interesting thing to look at. And it may be that there's that interaction between tissue development and microbiome establishment, that then leads to one phenotype or the other. Because again, I come back to the fact that this is not an outside-of-the-normal-range insult. What we have with the heat stress phenotype of the calves, or of the cows, is that they're not fully expressing the genetic potential that they have relative to the animals that are cool, but it's not a pathology. It's just within that normal range, we're pushing them to the bottom and the other animals are allowed to fully express what they're seeing. So it may be a combination of a number of factors that are allowing for that expression of the improved phenotype.
Dr. Jimena (51:49):
And to that note, Geoff we have talked about this many times, obviously we're sort of mammary gland center. But also we have find out that a lot of other tissues and organ systems within the animal are in fact that it's not all about the mammary gland. Obviously for a successful lactation, you need a functioning liver and, and other organs obviously. So even like in these heifers that we euthanize, we'd see smaller adrenal glands. So there's a whole story with the HPA axis and how they regulate stress in a way. And so those areas are also very important. Obviously heat stress is the center, but you know, other stressors. How they’re pregnant for a heck of a lot of time during their lactation, so there are many other times that cow will be stressed. And I do think that it's, it's about relieving those stressors to the problems of the cows. The cow’s are gonna produce- no they're made for that. It's our job to try to reduce those stressors and let her do what she knows how to do.
Scott Sorrell (53:01):
Excellent. You both have made a very compelling case that we need to cool those dry cows. Although cooling systems are not free, right? They're they're, they can be expensive. Can you talk a little bit about the economics of, of cooling cattle and where does it make sense or perhaps where it doesn't make sense?
Dr. Geoff Dahl (53:19):
Well, I'm gonna show my bias, but, you know, I used to get asked when we first started doing this work. I can only cool one group of cows. I can only invest in this, who do I cool? And for a few years, I would hedge and say, ah, probably your early lactation cows and then the dry cows. And then I've come off of that completely based on some of the economic analysis that we've done, right? The first group of cows to, to cool are the dry cows. Because not only are you going to have an impact on her entire next lactation, but you're going to have an impact on the calf that she's carrying for her three, first three lactations. And so when you think about the amount that it would cost you to cool your dry cows effectively, essentially one sixth of your herd, versus the entire herd, that's going to pay off a lot sooner than even cooling, And I know it's heresy, the early lactation cows. Obviously, I'm extreme there but I also think that asking the question that, you know, I can only cool one group of my cows is not the right way to frame the question. Can I afford not to cool all my cows?
Dr. Jimena (54:41):
I think it's about understanding too, that I think this is the take home for me, is that heat stress is not only impacting lactating cows. And if it does, it's not permanent, they will recover. And what we're seeing here are permanent effects that are very hard to overcome. And so it's not about who do we cool it's about, and Geoff can speak more to this. What do you have in place to make more sense, depending on your facilities and your resources, and then just figure out what's best for you. But yeah, they, they did a lot of work on that. And our, our last paper in JBS showed that when you add the losses that you have on those lactations of the daughter, does the number go off the road? And it's all our estimations. Right. But it just makes sense.
Scott Sorrell (55:44):
We're getting close to the end here, Stephanie just called last call, just wanting to make sure that there's not any big issues, big topics we haven't covered? You got a lot left. One more round Steph, another big beer. Oh yeah. Geoff, Geoff you're ...that’s empty! That's excellent. Are there any big issues that we've yet cover for the audience?
Dr. Jimena (56:14):
I'm going to throw a dart here? We didn't talk about the granddaughters too much, but we if add that into the equation. The, you know, the, the impact it's really, really amazing and we don't, we don't have, we have preliminary data showing that the survival and Geoff showed some of those graphs in his webinar. We have less and less animals. We're talking about 6 years after the initial insult, but we do see, and I was surprised. And I remember sharing this with Geoff. And we were like, yep, they produce less milk even like five, six years down the road. So it's amazing and it's really intriguing
Dr. Geoff Dahl (57:01):
Yeah, so to me, the sort of take home is that it's two programming events. That heat stress late in gestation is programing that cow to be less productive and potentially less healthy as she moves into that next lactation- she can recover from that. I think that we see some subtle effects, but I think that she'll recover in that next lactation, if she's appropriately cool. The calf is programmed as well, but she is programmed not only to be less capable of surviving in the herd, but also to produce less milk. And then she's going to transfer that lower capacity onto her offspring. And so we've got one that might be recoverable in the cow, but the dramatic effects are in those calves. And that's really where we're going to see a hit longterm.
Scott Sorrell (57:54):
Excellent, well, Jimena and Geoff: I want to thank you for this important conversation and for sharing your new ideas and new data with us. And of course, Clay, thank you for all the help and, and being here tonight. And thank you to our loyal listeners for stopping by it. The exchange to sit with us awhile, if you like, what you heard, please remember to drop us a five star rating on your way out. And remember you get a really cool Real Science Exchange T-Shirt just by hitting the “like” button or the “subscribe” button and sending us a screenshot along with your address and size to anh.marketing@balchem.com. Our scientific conversations continue on the Real Science lecture series of webinars. Visit balchemanh.com/realscience to see upcoming events and past topics. We hope to see you next time here at the Real Science Exchange, where it's always happy hour and you're always among friends. Cheers everybody. Thanks.