All right. Well, thank you for having me today. My name is Jimena La Porta, and I am an associate, professor in the Department of Animal and Dairy Sciences at the University of Wisconsin-Madison.
And my area of expertise is mammary gland physiology, and I particularly looked at the mammary gland of dairy cows. So I'm excited today to share some of the research that we have been doing in in dairy cows. So focusing mostly on heat stress, so I'm gonna give you a little bit of background on heat stress in dairy cows in general, and then we're gonna focus on the effect of heat stress prenatally, so in during late gestation, and how that can have an impact on three generations, the cow herself, her daughter, and her.
Granddaughter and also we're gonna have the second half of this presentation focusing on the postnatal effect of heat stress. So looking at the pre-weany calf, so this is from birth to weaning. So focusing on those first two months of life and how heat stress can have repercussions later in life and what can we do to provide heat abatement strategies for these young animals.
So I'm gonna start with some background on climate change and the impact that that's having on our dairy industry. I think most of you recognise that our temperatures are rising globally. Heat stress is not a regional issue anymore.
It's more of a global issue. And if you think of it globally, it's affecting some regions. In the US, in the Midwest, in Canada, Northern Europe, in general, that are highly populated with dairy cows, and several years ago, those were considered a low risk of heat stress, but nowadays we're starting to see more and more heat stress in those areas.
And unfortunately the predictions are Not great. By 2050, the USA in particularly, in particular, is projected to experience more frequent and intense heat stress waves and also temperature increases that are going to be of about 2 or more degrees Celsius. So that is very significant and it has an impact, direct impact on our dairy industry.
From the cow side, it will reduce milk production. For fertility. It's also a welfare concern and from the crop side, it reduced yield and quality of the feeds that cows are are, are eating.
So this is a concern that affects both the welfare production and also the crop quality. Now, when we think about heat stress, we typically focus on our lactating cows, and those are cows that are making milk on a daily basis, we're milking them every day. So this causes immediate effects on their production, health, and well-being, and overall sustainability of our farms.
So heat stress in lactating cows is gonna directly disrupt their physiology. They're gonna start shifting their energy towards heat dissipation. They're gonna start sweating more, increasing respiration rates, and overall, we're gonna see an increase in core body temperature.
They're going to decrease intake quite rapidly. We see between 20 and 30, even 40% reduction. In intake and this affects the way they utilise the nutrients.
It affects metabolism and all of that leads to the reduction in milk yield, fertility, and health. And as you can imagine, all of that will have direct significant financial losses to our industry. Now, luckily, we're well aware of this when we think about lactating cows and generally speaking, we adopt, adopt some heat mitigation strategy by using fans combined with water soakers, shade, and also nutritional strategies for our lactating cows to try and prevent the impact of heat stress in our herd.
Now there are other cows in our herd that are non-lactating, and this includes dry pregnant cows, ah, pre-weaned calves, growing heifers. Those heifers are gonna then become pregnant and start their first lactation. So these animals, Generally speaking, they have received less attention when it comes to heat stress abatement.
They are not a priority for, for heat mitigation, and there are quite a few reasons for this. I listed four of those that I think are most relevant. One of the reasons is that they are more heat tolerant and they don't require cooling.
There's this perception that they don't require cooling because they are not producing milk, so they are generating less heat. And although this is, somewhat true, I'm gonna show you today that they are also susceptible to heat stress and they can be impacted as well. So there's also this assumption.
That the cost of cooling outweighs the benefits. So in other words, because the high setup costs for cooling and for providing nutritional strategies for these non-lactating members of the herd is, is expensive for the farmer and there's also lack of infrastructure. There's this perception or assumption that it is not beneficial to cool them economically speaking.
Now, another reason that these animals, non-lactating animals are not a priority, could be the lack of immediate production outcomes, affecting revenue. As we said, heat stress effects are less visible in the short term in these animals, but I'm gonna show you how these can manifest later in life. So, Lastly, the, another possibility is that there's an underestimation or there's lack of evidence of these long-term effects that heat stress can have on dairy calves, on dairy heifers, and on dry cows.
So, one of the reasons is that there's limited research showing how heat stress in these animals can impact later in life despite they're not producing milk. And that has been the focus of my research here at UW Madison, where we have focused on the impact of heat stress on dry cows, on pre-weaning calves, and also dairy heifers. And I'm gonna show you how they are still vulnerable to summer heat, but the effects that happen in these animals are going to manifest later in life, even years after they were exposed to heat stress.
And the reason why this happens, it's because this heat stress is gonna lead to programming effect that are going to manifest beyond the heat of summer and consequently, they are going to generate less productive and less resilient cows and it's going to have economic consequences, but these are going to be more evident when we look at the over the lifetime of these animals. So, today I'm gonna focus on the dry cow and calves. And so one of the reasons why we focus on the dry pregnant cow, despite she's not making milk, is because in this cow, there are 3 generations.
Presented. And heat stress can impact all of those generations. So, the first generation is the cow herself, so the mother, the cow, the dry cow, and she's undergoing mammary gland evolution, regeneration during the dry period.
She's also pregnant during that time. The late pregnancy coincides with a portion of the dry period, so the foetal daughter is developing in utero at that time. And there's also a third generation that is represented here by the oocytes in the foetal ovary of the daughters, so the F1.
And we often not talk about, about this generation, . Often enough, but the foetal ovary of this daughter that is developing in utero has the germ line that will generate the granddaughters of this cow. So if this cow is under heat stress, During this period of time, during late gestation of their daughters, it can impact herself, the daughters, and the granddaughters.
So I'm gonna show you and expand on each of these generations and show you how they are affected in, in multiple generations. All right, so the dry cow is undergoing the dry period, so this is typically 45 to 60 days before she calves between two lactations. So we typically offer a dry period to, to dairy cows to allow for evolution to happen of her mammary gland, to allow those cells in the mammary gland to regenerate, and this will maximise the secretory cells at in the next lactation.
Now, this is what is happening during that dry period. We have the dry off, we have evolution, redevelopment, and the cells in the mammary gland are initially dying, so they are undergoing autophagy and apoptosis, so we want that to happen to give rise to more cells proliferating as that cow approaches parttuation. So we want this to happen in, in this Now, when a cow, a dry cow undergoing evolution and redevelopment is under heat stress, this is gonna impact the cellular turnover and it's gonna delay that evolution process that we want those cows to be undergoing.
So what we see is the same graph now, this is the percentage of cells, this is the dry off, and then what we can see here is that Heat stress is attenuating cell death via apoptosis and autophagy, you see here in the red and green, and that consequently inhibits proliferation later as the mammary gland is redeveloping and approaching parturition. So this is causing that mammary gland to start the next lactation with older cells and cells that are not regenerating properly. So when we look at the mammary gland in the next lactation of a cow that was under heat stress when she was dry, remember that this was a 645 to 60 days before she caves in and she starts her nextactation.
So when we look at her mammary gland, we see very striking differences in the microstructure of that tissue. This is a mammary biopsy that was taken. This example is at 2 weeks in milk, so she was heat stressed or not during her dry period.
So we can see how the mammary gland looks very different here. In red, we see the mammary gland that was heat stressed when she was dry, and here in black, we see the mammo gland of a cow that was offered heat abatement when she was dry. So she was not heat stressed during that dry period.
So you can see here that the heat stress, dry cow, mammary gland has fewer and smaller lobularbilar structures. They have fewer mammary epithelial cells in those structures and overall a less secretory synthetic capacity. So in other words, their mammary glands, their alveolar structures, which are the ones that are going to be secreting the milk.
You see these round structures here are smaller. And are fewer. So that mammary gland has not, does not have the ability to produce as much milk as that of a cow that was not heat stress when dry.
So we see repercussions that go beyond the entire lactation. So if this cow was heat stressed when she was dry, she will produce on average 5 kg less milk in her next lactation. So a period that is 5 to 6 weeks during the dry phase can have long-term effects for more than 40 weeks in their next lactation.
You see that the red line here indicates the malproduction of a cow that was under heat stress, and in black, you see the malproduction of a cow that was not under heat stress. So you can see that difference on average is 5 kg throughout the entire lactation. So again, a relatively short period of time under heat stress during the dry phase can have repercussion that lasts 40 weeks later in lactation.
One important thing to note here is that when these two groups start the lactation, they are all under the same environment, so that the only difference, whether they were heat stressed or cold, was during the dry period. So big impact on the cow herself. So that's the F0 or the cow, the the mother.
Now we're gonna look at the effect on her daughter. As I told you earlier, that dry cow is undergoing late gestation, so those last two months of gestation, and we all know how ge all phases of gestation are important early, mid and late, but here, the late gestation coincides with that dry period, so we can impact the daughter developmental. Physiology.
So this is the concept of foetal programming of the daughter. Like I said, the dry period coincides with the last trimester of gestation, and there's a lot of important processes happening in utero here. In fact, 70%, 70 to 75% of the, birth foetal weight of that daughter is going to be acquired during those last two months of gestation.
This is why this period is so important for organ growth and maturation. And it's highly sensitive to what we call developmental plasticity. This heifer, this, foetus is sensing the environment.
There's a lot of cellular events that are happening, cellular proliferation, differentiation, and functional organisation of all those tissues. There's what we call metabolic and endocrine programming happening in this last phase phase of gestation. And all of these processes are highly regulated by temperature.
So you can imagine if that cow is under heat stress, so will her foetus, because the foetus is going to rely on the mother for temperature regulation. Typically, the foetal daughter is not very good at regulating her own temperature, so she depends on placental dissipation of heat and when The cow is heat stress, the, the, the, the, the foetus is going to be under hyperthermia as well. So this is the problem when dry pregnant cows are under heat stress, it's because their foetus will be under heat stress, during that late gestation, so all of these processes can be potentially impacted.
And that's what I'm going to show you in the next few slides, how foetal hyperthermia during these 6 to 8 weeks during late gestation can have short but also long-term repercussions on that foetal daughter. So what we did here is we sum, we're going to summarise all those effects. And as you will notice, in utero heat stress, it's gonna trigger these negative effects that are going to manifest postnatally.
One of the hallmarks of in utero heat stress is reduced gestation length. So on average, these heifers are going To be born 5 days before expected. And so, not only that, but they are going to be born smaller and shorter in stature.
So overall they are going to be more petite and they are going to have lower milk and grain intake, so they are going to be consuming less milk and less grain during the pre-weaning period. Now, this growth retardation of these animals, these heifers at birth, is not transient. It doesn't go away, immediately, but it's, it's also, we can also see it even 300 days later.
So this from 0 to 60 is what we call the pre-weaning period and it's important to note that all of the heifers here, whether they were in utero heat stress or not, are going to be managed identically. So they're the same environment, consuming the the same feed, same management. Everything is identical once they are born.
And in this graph, you can see the hip height. So this is a measurement that we use to look at growth of that heifer, and what we can see here in the black lines are heifers that were born to an to that were in utero cool and in red in utero heat stress. So you see A pattern here that even pre-weaning and after weaning, even up to one year of age, the red bars are below the black bars, so that means that the heifers that are born smaller remain smaller for at least one year of age.
So this is not transient, it's quite permanent. And this is particularly evident when you look at the survival rate of these heifers. In red, you have the the utero heat stress daughters, and in the blue, in the black bar, you see the cool daughters.
So you can see the same pattern here, the red line is below the black line, and these are different Lifetime events. So from birth to when they lead the herd. So birth weaning, first AI, first calving, 1st, 2nd and 3rd lactation.
Typically, dairy cows remain in the herd for 3 to 4 lactations on average. So what we can see here is that if they are in utero heat stress, they are gonna leave the herd sooner. They are gonna have reduced survival to First cabin, this is about roughly 2 years of age, and when they start lactating, when they, they become part of the lactating herd, they are going to have reduced productive life.
So you can see that in the first lactation, we have almost 20% less of those in utero heifers making it to first lactation, second lactation, and third lactation. And when we look overall, we see a reduced lifespan of about 12 months. So this is quite significant.
Now, when we look at the milk production of these heifers, so those that make it to the 1st, 2nd, and 3rd lactation, they are going to be producing less milk. This is milk production. In the y axis, and this is weeks in milk.
The light pink is the first lactation, and then in the two shades of red, red, you see the 2nd and 3rd lactation of heifers in utero heat stress. Now, when you compare that to the production of heifers that were in utero cool, so they were not. Stress, you can see the striking difference in production of those animals and you can see how much loss of milk those are experiencing in the 1st, 2nd, and third lactations as you can see here.
So if you look at, for example, the 3rd lactation of in utero cool heifers here in the cursor, can see that they are above 90 pounds or 40 kg of milk for several weeks, whereas if they were in utero heat stress, they barely make 90 pounds and they are above that only one week at peak lactation. So you see all that loss in milk that in utero heat stress is Triggering. So, in utero heat stress, it's gonna lead to heifers that are less productive and are going to have a shorter lifespan as I showed you already.
Now, our lab has this question and we have been chasing this for several years now. So how is it possible that these adverse intrauterine temperature conditions, this hyperthermia in utero, is affecting, The short and long-term effects in that foetal daughter and how this is is impacting the the overall survival and productivity years down the road. So I'm gonna walk you through some of the main things that we see in this heifers.
So one of the things that we see is immune function. So these heifers have reduced immunoglobulin absorption from colostrum. So basically, we offer the same quality colostrum and they consume less, but also the apparent efficiency of those immunoglobulins is reduced.
On average, between 10 and 20% less if they are. In your heat stress, and that leads to lower immunoglobulins throughout the pre-weaning period. So those first two months of life, uro heat stress heifers have lower immunoglobulin concentrations in their circulation, and that leads to a less robust immune system.
These heifers are gonna get sick more often. We're gonna need to treat them a lot more and so they, they become sort of a, a nightmare for veterinarians. When they have to treat them, clearly, a lot more costly to raise and especially because they are going to leave the herd sooner, no matter what we do.
So, another thing we see is impacts in gastrointestinal development. So these heifers have more cells undergoing apoptosis in their God, so it's particular in the genome, we see that there's more cell death cell death than cell proliferation in this, in utero heat stress heifers, and we don't want that in a growing tissue at this point in time, we want more cells proliferating, that tissue is growing, it's undergoing cell turnover. So what we hypothesise here is that in utero heat stress is trigger triggering an accelerated gut closure.
So that exposure to high temperatures in utero is triggering a more quick cell turnover. So when they are born, they have a deregulation of cell death to cell proliferation, and this is one of the reasons why they are not able to absorb those immunoglobulins from lostrum. So that leads to those health effects that we see later on and impaired immune function.
Another thing that we see, which is very interesting is impacts in the ability of these animals to regulate temperature. So we see that in utero heat stress heifers have altered the temperature set point. On average, these heifers are gonna have 0.2 °C higher core body temperature.
And remember that the only insult was in utero, so this temperature, core temperature increased through. About the pre-weaning period is without any treatment here. We measure the rectal temperature 3 times a week and what we see is that the utero heat stress heifers have overall higher temperatures of their body.
So that is Not great from a body temperature regulation standpoint. And when we look at their sweat glands, what we see is that they have big alterations in the sweat gland density and distribution in their skin. They have less and smaller sweat.
Glands as you can see in this photo in the red, you can see in urohitra heifers that they have smaller and less sweat glands in their skin and they are located deeper into that skin. So they have a harder time thermoregulating and that leads to those higher temperatures. Another thing, interesting thing that we see is this in utero heifers, in utero heat stress heifers have larger adrenal glands.
And this is important because the adrenal gland is secreting cortisol, and cortisol, as you might know, is the hormone, the stress hormone. So what we see is that the histological evaluation of this adrenal gland at birth and at weaning, we see larger Adrenal glands and the thickness of all the zones in that adrenal gland that are secreting different hormones are impacted, so you can see the huge difference in size and in the thickness of the, of the zone. So this has a potential impact on the way these animals are going to respond to stress during the pre-weaning phase and potentially future stressors in life.
Another thing that we see is the ovaries, the ovarian and follicular development of these heifers is also impaired. This is the ovary adrein, so this is two months of life. We, euthanize these heifers and we look at their ovaries.
You can see how they look in an in utero full heifer. This is normal, but in an in utero heat stress heifer, look at the difference in the size of those ovaries. They are, .
Very much reduced in size and also we see that they not only have smaller ovaries, but they have fewer secondary follicles and those ovaries and follicles make less AMH or anti-mullarian hormone as you can see in this graph right here. Throughout the pre-weaning period, you see that red line below the black line. These are the neuro heat stress heifers versus the neuro cool.
So the AMH is a marker of ovarian reserve, and this can have impacts in their future fertility, as you can imagine. And we also, when we go in later in life at 12 months of age, at puberty, we do a scanning of their ovaries and we see that they still have smaller follicles and a smaller corpusothium at that age, and they also have less systemic oestrogen at that age, which is very important when we're trying to get those animals pregnant after they reach puberty. So impacts on several tissues and one of the ones that I'm most interested in because I'm a mammary physiologist, is the mammary gland.
So typically when we think about the mammary gland, we think about a lactate in cows, but mammary gland development starts very early in life, actually. Before the animal is born. So what we see here is that if a heifer is in utero heat stress, her mammary gland is going to be impacted.
So they have smaller adds compared to in utero cool heifers. They have lighter parenchyma tissue and lighter fat fat. When we dissect this mammary gland, we see there's parenchyma and fat fat, and both of those tissues are lighter, and we will look at the histology, which is what I'm showing in these two photomicrographs, we see that the inutero heat stress parenchyma is, is under, it's underdeveloped, so we see less ductal.
Structure, less branching morphogenesis, and a reduction in the proliferation of those cells that at this point in life, this is at we, this is at 2 months of age. These are mostly ductal epithelial structures that are going to give rise to the alveolar structures later in life, but even starting life with a mammary gland parenchyma that has less potential to develop, it's very striking to see. When these heifers reach first lactation, so this is 2 years after, we see that their mammary glands are still showing these phenotypic differences.
We see a reduction in lobularveolar development. When you compare these two tissues, we see fewer and smaller alveoli, as you can see these round structures here that are Producing milk on a daily basis, they have fewer mammary epithelial cells and 30% less proliferating cells. You do see also a lot more connective tissue, which in a lactating gland, you want to maximise your secretory cells versus your stroma tissues.
So we can see here that these glands are phenotypically. Impacted and they also are gonna lead to less milk production in those heifers, as I showed you early on. So, remember that this is an in utero heat stress heifer that 2 years after she started making milk.
So we see those effects that are still evident 2 years after they are born. Now, what we learned from this is that this early life mammary development matters and the development of all the tissues that I show you in terms of the skin impacting thermal regulation, the adrenal gland potentially impacting stress physiology, the gut impacting the ability of those heifers to absorb immunoglobulins and the immune organs as well and also the mammary gland and the ovary. Are also impacted in early life in utero, but particularly the mammary gland, is setting the foundation of how much secretory tissue those are going to have in their first lactation, and that's going to be dictating how much milk they can produce.
So stressors in early life, even before those animals are born, can have long-term repercussions in the ability of those cows to make milk. Now, I show you the effect on the cow herself by heat stress during the dry period, the effect on her daughter that it's been just stated by the cow, and now we're gonna see the link between the F1 and the F2. Remember I told you that the ovary of this foetal daughter is going to have or going to be developing the ocytes that will give rise to the next generation two years after.
And so the connection between the mother, the daughter, and the granddaughter, it's, it's in utero via this germ line that I'm I'm showing you here. So this germline is indirectly exposed to in utero heat stress. So I'm gonna show you here how the granddaughters can also be impacted.
This is the survival rate of the granddaughters of heat stress dry cows. So we did a retrospective analysis of lifetime records. So basically, we have 10 years' worth of data where we can look at what happened with the F1s and what happened with the F2s from birth to when they leave the herd.
So these are the granddaughters and you can see The pattern here where the red line representing the granddaughters of heat stressed dry cows is below the black line that represents the granddaughters of cool, dry cows. So you can see that early in life we're losing a lot of granddaughters. In fact, 26% less granddaughters of heat stressed right cows lead the herd before first calving.
This is before 12 months of age. And overall, they have a reduced productive life. So we're losing more, not only daughters, but we're losing more granddaughters.
So again, these are the daughters of the daughters. So I know it's a mouthful, but this is the 2nd, the 3rd generation impacting the productive life. So this is very economically costly.
So we were interested in looking why are they leaving the herd soon and what we did in this Study is we look at, OK, in those granddaughters, we look at feed intakes, AEA, IgG levels, we look at growth trajectory, we look at the mammary gland to see if there were any phenotypic differences in those heifers in those F2s, and strikingly, we see no differences at all. So if you look at those granddaughters from birth to weaning, they look identical phenotypically. So if we were selecting these animals based on growth trajectory, we would keep them all.
And so what happens is when you look inside the mammary gland, this F2 will have smaller parenchyma and smaller fat pads. So Typically they look identical, but when you start looking inside the tissues, particularly the mammary gland, in this case we did mammary ultrasounds, you see that they have smaller parenchyma, smaller fat pads, and when you look deeper into their histological phenotype, you see that the granddaughters of heat stressed dry cows have less proliferating cells, they have, more cells dying, they have lower expression of oestrogen receptor which is very important for sub-proliferation. They have smaller ductal epithelial structures.
So overall, there, these are unfavourable characteristics for a mammary gland that are going to lead to these granddaughters making less milk in their first lactation. So we have first lactation for these F2s. We don't have 2 and 3rd, but we, I assume that they are going to also be impacted.
But what we see here is the granddaughters of heat stress dry cows are gonna produce on average. 1.5 kg less per day in their entire lactation.
So we have to think about that this is 4 to 5 years after the original exposure of heat stress of their grandmothers, so that dry cow. So if we kept those at 2s that came from a heat stressed dry cows, now they are going to be producing less milk. So, I, I guess, it's important to think about the long-term effects because of this.
So we see effects on the cow herself, 2 to 5 kg, because heat stress during the dry period interferes with the mammary landing pollution and redevelopment. So those cows are going to produce less milk in their next lactation. We Impacts on their daughters from 2 to 6 kg less milk in their first to third lactation, and we're now seeing effects on their granddaughter, so that 3rd generation because of the impact of the foetal ovary.
Now, in this last part, I want to focus a little bit on the effect of heat stress in pre-wind calves. We talk about the prenatal, now we're switching to the post-natal effects. So there's this perception that heat stress, that pre-wing heifers are not impacted by heat stress, they are less vulnerable.
They are more thematolerant and better able to cope with heat stress. This video, you can see that that heifer is breathing very hard, she's stressed, and the reason why this perception I, is, permanent is because we don't see, tangible effects on production, and these heifers are not typically offered he ate, just like in dry cows and growing heifers, but I'm gonna show you how hot and human environments can really be stressful for them and what we can do to prevent those growth and health outcomes of these heifers that are under heat stress by cooling them. So there are things that we do, here in the US, hatches are very, are, a way we, we house calves, heifers, mostly for, winter, but in summers, these hatches can get very warm.
So what we do is we provide supplemental shade, we change the orientation of those hatches to also add extra bands as we can see here, elevate the hatch, all of that to maximise natural air. There's also group housing, that it's, more common nowadays, either in pairs or in larger groups. These are going to be generally indoors, so, we focus mostly on ventilation for air quality, but there's really no guidelines on what airspeed these he should be exposed to to ah provide cooling during summer and there's very limited research on Provision of mechanical ventilation for pre-wan calves during, during summer.
So we wanted to do this, we want to focus on on cooling mechanisms by implementing mechanical and evaortic cooling for pre-weaning calves during summer in different climates and in different housing types. As you know, and I'm sure it's common there too, there are many different ways we can house our, our, our pre-weaning heifers, so we have to open the black box a little bit and be creative. So what we did is in this first study in Florida, we provide fans to group house heifers with these barrel fans, these are 42 inches in diameter, and we have one oscillated fan above the ground.
So what we see here is improvements in thermal regulation, particularly promoting. Cooling via those fans. So we were able to reduce rectal temperature by 0.25 °C.
Respiration rates were reduced by, by 15 breaths per minute, and skin temperature was reduced between 1 and 2 °C depending on the time of the day. But overall we see positive effects of providing these fans, promoting convective cooling to pre-wind heifers. We see that these animals, really enjoy that, extra speed of the fans.
They drink more milk even during the hottest time of the day. In this case, we were using automatic feeders, so we were able to collect a lot of data, from this experiment and we see that, the heifers that have access to those fans were able to drink the full allotment of milk that we give them, they drink it faster and they keep coming for more. They were not satiated, and we were offering.
10 litres per day in this study. So if they were heat stressed, they were not eating during the hot times of the day. They were drinking slower, they weren't drinking the full lot, man.
They were coming more often but drinking less. So providing funds was able to improve that. Also, we see some interesting postoral behaviours.
If they are heat stressed, they are going to be more lateral, like this. In this photo, lying laterally to maximise the heat exchange with the surface of the sun in this case, and if they were, if they had access to the fans, they were lying more comfortably like you can see in that photo. And we also see improvements in treatments and medications, so those heat stress heifers were sick more often and they had to be treated more, so providing funds was able to rescue that.
In Wisconsin, there's a lot more outdoor hatches, as you can see in this photo, so we have to get a little bit creative there. And what we see here is we use solar panels that power these fans, so we were, we were redirecting the air inside the. Hatch, and this is a video of the internal view of that hatch.
If you have worked with calves in the summer in hutches, you know that it gets really, really warm inside that hatch. So what we were wanting to do here is provide active ventilation inside those hatches, and we were able to do that, so the air speed inside that hatch was between 1.8 and 2.1.
We did this short first prototype for 4 days. We had 3 week old heifers. We showed that we were able to improve thermal regulation when those heifers were actually inside the hatch, so we had to do some restrictions inside and outside and we estimated differences.
So we see lower sweating rate, lower respiration rate, lower skin temperatures, particularly in the morning. So we see some benefits of providing these funds in hatches. But we do see, we noticed, a little bit of noise and those heifers, were spending a little bit more time outside the hutch.
So in order to fix that, we created this second prototype where we bifurcated this tube. In this case, we use younger heifers, so we started 3 days of life, and we went all the way for until 28 days of life, so for 4 weeks, and we did it. Continuously in the first prototype, we turned the fan at night.
Now we provided day and nighttime ventilation, and what we see also is by doing those inside and outside restrictions, we were able to improve thermal regulation when those heifers were using the hatch. So we see reductions in skin temperatures and also in rectal temperatures when the heifers are inside those hatches. And most important, Currently, we see air quality benefits for, from providing this active cooling inside hatches.
As you know, urine ammonia accumulation in these hatches is, it, it can be very damaging to, to lung health and it can have respiratory effects. So this fast moving air inside the hatch was able to remove ammonia buildup and Moving that still air inside the hatch and when we sampled the air, we were able to see that those hatches have less colony forming units if they have that continuous air blowing inside them. So benefits in the microclimate of these hatches.
And this is the 3rd prototype where we provide continuous airflow with daytime misters. This is in Georgia, calves were housed outdoors in these wire hatches, so we provide this actual fan and this drain tube. And we have fans 24/7 and during the day, we have misters providing some the water as well.
It was very hot in Georgia and we did this in collaboration with the during an initiative and collaborators at the University of Georgia, so we wanted to provide more air to more camps in an outdoor setting. So what we see here is we see improvements in airspeed as we expected, especially when the cap was closer to the tube, but also when they were a little farther away as the day progresses. So we see that overall the air speed is, is always higher compared to hatches that did not have these tubes.
So you can see the air is pretty negligible in, in those hatches. We also see improvements in thermal regulation. These heifers that had access to these tubes providing air air, continuous air had reduced skin temperature, reduced respiration rates, and reduced rectal temperatures as well.
And we see improvements in their behaviour and activity. We also see, that they spend a lot more time closer to the tube even during the nighttime. And now we're doing another project this summer in Wisconsin where we're providing these tubes to indoor individually housed calves.
This is a quite a normal setting for calves in, in, in the Midwest as well. So what we're trying to do is provide cooling to different housing types, different regions within the country to be able to provide cooling mechanisms to these calves during early life and hopefully see benefits later in life. There's still limited research in this area and the, the connection between early life and future production.
So we're trying to come up with experiments to, to really show the benefit of that development. Plasticity, so avoiding heat stress in utero and heat stress during those first two months of life to benefit from cooling the dry cow and the calf once they are born, to avoid hypothermia in that plastic window of time where we can influence the development of the calf and influence them for a lifetime. So, in summary, some summary and conclusions from this presentation, one of the things that it's important to think about as we approach summer is that heat stress can have effects that are beyond just lactating cows in summer.
So we have to think of this, Long term and the impact that it can have for three generations down the road, so beyond summer and beyond lactating cows, it can impact the dry cow, the foetal daughter, and also the generations that are coming after that. So the The effect of heat stress, it's not just summer, it can have long term effects. Pre-wind calves can also benefit from cooling.
We're seeing very positive effects of these different strategies that we're implementing, and we're now trying to look at the long term benefits of that. So, sort of some excuse me, recommendations will be to monitor dry cows and monitor calves in summer. And provide heat abatement.
When possible, to protect this calf during early life development. Allowing them to, to, to express their full potential when they become cows and establish that long-term performance from the get-go. So minimising the long-term generational effects that heat stress can have in this dry cow and multiple generations.
So with that, I would like to thank collaborators, graduate students, undergraduate students, postdocs, and, and visiting scholars that have been involved in all this research. Also funding for to perform all these experiments from USCA South Web milk, the Innovation Hub, Wisconsin, Florida, and also donations from Purina and Sybeg and I would like to take any questions.