Heat stress research to find the best solutions: Trial update from Scott Farm | Ep. 118

Heat stress is a growing challenge on our dairy farms, and the impact on your farm could be bigger than you think. In this episode, you’ll hear how DairyNZ’s summer trial at Scott Farm is testing common mitigation tools, and assessing their return on investment, to find the best solutions.

Animal scientist Dr Charlotte Reed and senior animal care specialist Jac McGowan break down the research and share their early insights and observations from the trials. They also share current information and practical solutions you can use right now to keep your cows comfortable and productive in the heat.

Heat Stress research and current information

DairyNZ invests in heat stress research to give you evidence behind the solutions that improve cow comfort, protect performance, and support sustainable, future‑ready farm systems.

Read more about heat stress research in action at DairyNZ

Get current information for reducing heat stress in your dairy cows

Have feedback or ideas for future episodes? Email us at talkingdairy@dairynz.co.nz

Connect with DairyNZ

Stay up to date with advice, latest research, tools and resources. Read, browse, scroll, listen, or be there in person. Visit dairynz.co.nz/get-connected 

Transcript

Welcome

SPEAKER_02 0:01

Kiora and welcome to Talking Dairy. I'm Odette Chauncey stepping in as host on this episode while Jack takes a turn in the guest seat. It's great to have you with us. You might have seen our heat stress information, which has been out for a little while this summer, but at the same time, we've also got live research underway at Scott Farm. So we thought this was a good opportunity to give you an update on the trial that's happening. Farmers have told us that they want clearer answers on what works, what it costs, and whether it's worth the investment. This research is all about getting that information for you today. Today we'll talk about the trial, where it's at, what the team is seeing so far, and what farmers around the country have been sharing about heat stress on their own farm. We'll also cover the practical things you can do right now while the research is underway. I'm joined by animal scientist Dr. Charlotte Reed and Jack McGowan, senior animal care specialist, who are both right across this work. Tell us a little bit about yourself and your role at Dairy NZ. Jack, you kick us off.

SPEAKER_00 1:00

Thanks, Odette. Yeah, so I'm a senior animal care specialist at DairyNZ. I grew up in dry stocks, so it was almost inevitable I would end up curious about and working with animals. I thought it would be snakes or camels, but cows was easier to get into in New Zealand. So I started as a research tech and eventually moved into development and advocacy. I was also a dairy farmer myself. I shameled for 10 years here in the Waikato. And these days my focus is on helping farmers manage challenges that affect cow welfare and productivity.

SPEAKER_01 1:33

Charlotte? Yeah, thank you. So I'm an animal scientist here at Dairy NZ. I'm originally from Northern, so very familiar with hot summers. So it is a bit of an interest of mine. I work across a couple of projects here at Dairy NZ. Over the last few years, I've been increasingly working with sensor data sets and what those data sets can tell us about cow experience on farm. And that has sort of naturally led me into this heat stress project, leveraging sensor data to give us more insight to how the cows are experiencing summer and what we can do to help farmers manage them through that period.

SPEAKER_02 2:08

Beautiful. A rich background there from both of you. So I can't wait to uh hear the conversation that we have today and what gets explored. But before we get into that, I just have a short quick fire questions for you both. I'll throw out two options and you have to choose one of the options. So no overthinking. So it's a hot day, you're sitting behind the cows. Are you eating an ice cream or having a cold drink?

SPEAKER_00 2:33

Oh, having a cold drink.

Why Heat Stress Matters

SPEAKER_02 2:35

Ice cream. I'm having an ice cream. Ice cream every time, Charlotte. How good? Definitely. Solid cold drink. Quick answer there, Jack. So no questions asked. Second one. It's a hot day. Are you in the milking shed or in the tractor? Milking shed. Oh, always in the milking shed. Always in the milking shed.

SPEAKER_00 2:55

With the cows. Yeah, with the cows. It's often cooler there. Or mind you, modern tractors have really good air con, but we never had a modern tractor.

SPEAKER_01 3:03

All right. Summer or winter? I'll complain about both. Winter, I suppose.

SPEAKER_00 3:10

Yeah, I think winter's easier to deal with.

SPEAKER_02 3:13

Cool. Let's dig into the detail a little bit. What prompted this focus on heat stress? Charlotte, I'm interested you already mentioned it a little bit. Could you talk some more on that?

Building The Grazing Heat Load Index

SPEAKER_01 3:22

Yeah, so the heat stress project we've got going on at the moment is a three-year project. And the ultimate goal of this project is to provide farmers in high-risk regions for heat stress the information they need to manage cows through the summer. So we're currently in year two of that project. We've been working in heat stress for a number of years, and the first year of this project was really around consolidating that knowledge from the previous work we've done as well as what farmers have been telling us. So our previous work we've done has been to develop a grazing heat load index, and that's a weather-based index that allows us to predict or assess the risk that cows grazing outdoors will be experiencing heat stress. It differs somewhat from traditional metrics for heat stress used in house systems, in that it brings in weather variables that our cows outdoors are going to experience. So, such as wind and also solar radiation being quite a big one. So we worked alongside Fontera and AgriSearch to develop that index, and that has now allowed us to look at where our high-risk regions of heat stress are. So using the index, we were able to predict the number of heat stress days that places across the country will experience, and that helped us narrow in that Waikato, Bay of Plenty, and also Canterbury are high-risk regions for heat stress and also major dairy regions. For this project, there was a need to focus on making sure those regions have the information they need. So, as part of consolidating information, we actually went out to 350 farmers across those regions to understand what they are doing, what practices do they have in place, what are they seeing, and what are their views and attitudes towards heat stress? How much of a priority is it for their farm? So that's what we've been doing so far in year one of the project. And now we're working on acting on some of that information.

SPEAKER_02 5:22

And what are the four weather variables that come into the grazing heat load index, Charlotte?

SPEAKER_01 5:27

It is temperature, solar radiation, and wind speed.

SPEAKER_00 5:31

Three in fact. As Charlotte said, we did a survey of 353 farmers in those regions of high risk. So that gave us some sort of high-level understanding, and from that we got the different perspective in Waikato Bay of Plenty versus Canterbury, and we wanted to understand in more depth on that. So then we ran some focus groups down in Canterbury and workshops in Canterbury and the Waikato, and they were about really digging into what those farmers were experiencing and what they needed, stuff that you can't really get from, you know, a very quick phone survey.

SPEAKER_02 6:08

Charlotte, it's really interesting to hear about the modeling and the grazing heat load index. It's super important that our research is relevant to our farming conditions here in New Zealand. The farmer survey also sounds fascinating. What did you hear from farmers across the country?

SPEAKER_01 6:22

Yeah, so one of the major things we heard from those 350 farmers was that across all three regions, farmers are really good at recognizing the signs of heat stress. So the vast majority could tell us something about what they would expect to see when cows are heat stressed. So that was really good to hear. But when we dug into that deeper, we also found there were some real regional differences between Canterbury and then Waikato Bay of Plenty, with those two grouping together a bit more. So one of the questions we asked was about how much of a problem they saw heat stress. And generally in Waikato Bay of Plenty, farmers saw it was an issue. Some of them it was less of an issue because they're actively mitigating it, but they still saw it as something that they need to have front of mind. Whereas in Canterbury, almost a quarter of farmers saw it as not so much of a problem at all. And there was sort of a couple of reasons they gave for that. So that was really interesting for us because the modelling we've done is showing that Canterbury is a high-risk region. But some of the farmers in that survey said they weren't seeing that on their farm. Another interesting metric we had in the survey was we asked farmers to tell us how many heat stress risk days they thought they were experiencing on their farms. And that was something we looked at in the modelling. It was somewhere between 15 to 25 days a year where their cows were at risk of heat stress. And that is really different from our modelling, which puts it between 67 to 80 days where cows are at risk of heat stress. So they can recognize the signs, but there was some evidence that they could be underestimating the problem relative to what the modelling tells us. So that was sort of something we were keen to dig into a bit further. Another sort of clear message we got from that survey was that even the farmers who are actively mitigating it or seeing that heat stress is a relatively small problem for them were interested in reducing it further. So that gives us a pretty strong mandate to work in this space and collate the information on how farmers can effectively mitigate heat stress on their farm.

What Farmers Say Across Regions

SPEAKER_00 8:31

That idea that even though they're seeing it as a small problem or they're already doing a lot to mitigate it, but they still want to do more reminds me of a a workshop that I ran some years ago now. It does connect to this work, where I asked the farmers to put a number on how low they wanted to get heat stress for their cows, and they found it really hard, a lot of hesitation. And when I asked them why, they said it was because for them, like no amount of heat stress was okay. Actually, what they really wanted was for their cows not to experience heat stress at all. But you know, the reality of farming is you're often stuck between wanting to do more and not being able to or not knowing quite how to do that.

SPEAKER_02 9:12

Sounds like there is a bit of a gap there between wanting to do more and having a plan, which I can relate to, you know, that desire to want to help or to motivation to make a change, but then not quite sure on how to go about it. So what is going on there?

SPEAKER_00 9:25

Yeah, so it's definitely not about farmers not caring. It's about needing evidence that the investments they make will pay off. So they're wanting to do the right thing or make the best decision for their cows within the constraints that they're working in. Some farm setups make it harder, like there's in historical infrastructure decisions. You know, down in Canterbury, we have pivot irrigators. You know, they don't work very well with trees in the way. Farms up here in the Waikato have often been joined together, and so sometimes the water supply will have quite narrow bore pipes, which makes it harder to meet the cow's drinking needs or pump a lot of water once it becomes a bigger farm. So they're working with constraints like that that are very difficult or expensive to try and resolve. So yeah, farmers who don't see it as a problem, they're more likely to say the cost isn't worth it, or that other priorities matter more, or that the cows can handle it. And definitely some of that is true, and some of it is actually just a a protective thing that our brains do, which is when we can't fix a problem, we need to make it smaller so that we don't feel bad about it. You know, that's completely normal human behavior. But the ones that are ready to act, they were really clear. They want data on return on investment before committing resources.

SPEAKER_01 10:46

Another thing we quite commonly hear is where the share milkers are on farm and they're seeing the cows day to day and that they're hot, but the farm owner is off farm and not necessarily seeing that. So bringing that cost of investment into the discussion can really help them when they discuss with their farm owner to show the benefit of putting mitigations in place.

SPEAKER_02 11:07

And it's um big investments. So they're never a small ticket item, are they? Some of those things. And like you said, Jack, with the pivot irrigation there as well, some other complexities going on. It's really interesting what came out of the survey. And Charlotte, what did you hear in the workshops? Were they similar themes, different?

Investment Barriers And Farm Constraints

SPEAKER_01 11:24

It was a bit different. We had workshops in Canterbury and Waikato. I participated in the Waikato workshop, and I would say all of those farmers really cared about their cows, and they really saw heat stress as something we should be effectively managing. They were quite innovative people, really. So what we saw in that survey was people want to reduce heat stress further, but what are the strategies? So in the workshop, what we were doing is saying, where are the research gaps? What is the information that we need to provide farmers to help them make this decision? As Jack said, there's that understandable reluctance to invest without a clear idea of what the return on investment was. So something we talked about a lot in those workshops was the value of different mitigations and how they compare. So, you know, if you're using sprinklers on the yard, is that better than going once a day to avoid the afternoon walk to the shed? So there were conversations about that, understanding the value of different mitigations and what the impact on the cow is. There was needing to know in Canterbury, is there enough proof that heat stress is an issue? What is the evidence we need to provide to tell ourselves and farmers that, yeah, this is something that should be more of a priority? Across both regions, they were really keen that we nailed down a bit more what the impact of heat load is on milk production. But really in Waikato, the focus was around those practical tools. When do I mitigate? What is the cost-benefit of mitigating? Also, interest in some of the nutritional strategies for heat stress. And then guide on if you're doing some of the simpler things like sprinklers or misters on the yard, how do we best put those in place?

SPEAKER_02 13:12

Lots of questions at hand. And there's definitely the infrastructure, the options that are available, but then what to choose, and there's a few things going in there. So, Charlotte, what is the research telling us? I can I know it's still early days with the trial, but can you talk us through a little bit of what's happening on Scott Farm, what you're testing and why, and how this all helps?

SPEAKER_01 13:33

Yeah, so off the back of those workshops, we had farmers sort of rate which of the questions were most important, and one of the ones that clearly came through was how effective these common mitigations are and how to best put them in place, right? So for this summer we planned a research trial where we have herds of cows on the research farm that over the summer will be under different mitigation strategies. So we have a herd that's gone once a day through the summer to avoid that afternoon walk to the shed. We have a herd that is shaded, so they are spending their daytime in a shaded area under trees. We have a herd that is getting a water mitigation on the yard. So there's in fact two herds. One is getting misters on the yard with the intent to use that cool water mist to cool the air around the cow, whereas the other group is under a sprinkler where the intent is to use larger water droplets to wet the cow and saturate the coke. And then our fifth group is our control, who are having a hot summer without any mitigation to act as a control. If you didn't do anything, what would that look like? And then for those five herds, we're looking at what happens to their milk production, what happens to their behavior, and what happens to their physiology. What is the impact of those mitigation on them?

SPEAKER_02 14:56

Super cool. I can speak from experience of being around the lunchroom break table and deciding whether it should be misters this summer or sprinklers this summer. And it's been a tricky conversation to pin down on which one it should be.

Workshops: Priorities And Research Gaps

SPEAKER_01 15:10

Yeah. And that's something that every farm has to decide. So our sort of goal with testing this range of options and in this project in general is not to say this is what you should put in place, but to provide information around a range of different strategies, like a toolbox of options that farmers can then look through and say what's going to work best on my farm within the constraints I have.

SPEAKER_02 15:35

Very cool. It's amazing to hear that whole journey come through from what the farmers have shared with you and what you're applying this year in the summer for the research down at Scott Farm. I'm also intrigued, Charlotte. Obviously, there's the Scott Farm team out there on the bikes with the cows. What are they seeing? Is there anything anecdotal coming from them?

SPEAKER_01 15:53

Well, yeah. So I mean, look, the strongest association we find in our heat stress trials tends to be run a heat stress trial, get rain. We started this trial on the 12th of January, and it hasn't been the hottest weather, it's been quite wet. But interestingly, even though, you know, the conditions haven't been as hot as we sometimes see during the summer, we have seen differences between the groups under treatment. So this is like very preliminary, but what we're just seeing is differences in their breathing rate. So breathing rate of the cow or the respiration rate is a key metric we look at in heat stress trials. When cows are hot, they breathe really fast. So that's something that we've the technicians have been monitoring in these cows, and we are seeing differences between that control group that is not having any mitigation and the other groups.

SPEAKER_02 16:48

I'm really curious at what point does a cow feel heat stress? You know, are we talking like 30 degrees, 20 degrees, 40 degrees? Where's that range? And then what does those misters and sprinklers, how do they help the cows in th those conditions?

SPEAKER_01 17:04

Yeah, so a cow's thermonutral range, the range of temperature at which they're comfortable, is much lower than humans. So where a cow exactly starts to feel heat stress is quite a research question for us that we've been working with. We usually say, you know, as you get over 20 to 22 degrees, cows are starting to get hot. But the specific conditions they're under at that temperature range, such as, you know, the wind, the humidity, can all add into that. But yeah, it's certainly a big question for this research project beyond this current trial overall, is what are the conditions when cows start to get heat stress? Where is that threshold? And then what can things like sensor data or animal behaviour tell us?

SPEAKER_02 17:49

Awesome. And then how does the sprinklers and the misters help in those conditions? Also, 20 degrees. If I'm feeling nice, I'm gonna assume the cows are a little bit on the warm side.

Inside The Scott Farm Trial Design

SPEAKER_01 17:58

Yeah, yeah, pretty much. So the sprinklers and misters work slightly differently, and that was something we talked a lot with farmers in our workshop about how they work and how to get the best out of them. So the mister creates a much finer water droplet, and the intent with misters is to cool the air above and around the cows. Whereas with sprinklers, it's a larger water droplet, and the goal is to saturate the cow and wet her coat so she cools that way by the evaporative cooling rather than cooling the air. They're different strategies, and what you're looking for to check each system is working well is different. With a sprinkler, you should see water rolling off the cows and a saturated coat. Whereas with misters, you're not necessarily going to see that. It's a finer mist through the air.

SPEAKER_00 18:49

What kind of change in behaviour would you see on the yard?

SPEAKER_01 18:53

Yeah, so that it was actually quite stark on the first days of the trial. We're all down there watching how they'd go on the yard, where some cows are under these sprinklers and misters, and some are are unmitigated on the hot concrete. And we did see quite a difference in that those control group cows who are not getting any water mitigation and are just on concrete were a lot more agitated. Farm staff and our technicians noted that quite clearly. So a lot more milling around compared to the cows under either the sprinklers or the misters who were very quiet. So quite a noticeable difference there.

SPEAKER_02 19:28

So I remember on the farm we had the cow Jerry and, you know, Jerry always came in and she was hot no matter what, even with the sprinkler on. So do you see that difference between cows and the groups?

SPEAKER_01 19:40

We really do. In any of our heat stress data sets, we see quite a bit of individual variation. Some cows seem to be more susceptible to heat stress. Another big question in this project is understanding that individual variation. And we've collected a few data sets, some from commercial farms and some from research farms, which we're going to be digging into deeper in the coming months to try and understand, you know, who is most susceptible to heat stress, what are the characteristics of those cows?

SPEAKER_02 20:10

Jack, while the research is still underway, what can we do on farm right now to reduce heat stress? You've already talked about a few of those options, you know, the sprinklers and the shade. But what can farmers get going right now?

Early Signals: Breathing And Behaviour

When Cows Feel Heat And Why

SPEAKER_00 20:22

Essentially it comes down to avoiding heat in the first place. And then if you can't avoid it or you can't avoid it all, helping your cows get rid of heat. So cows will actually manage that themselves if we provide the opportunity for them to do that. But it's not always possible in our farm systems. We usually need to actively manage that risk and mitigate for them. The first thing is to watch for the signs, and farmers are really familiar with these. Might not always see them if we're not out on farm. You know, it might be our farm employees who are seeing those signs, so you can talk to them about it. But it's things like breathing faster, panting, bunching up, you know, they're looking for shade, they're hanging around the water troughs. They're not grazing during the day as much. So you might see that as reduced activity. And then you're looking at ensuring that they have really good access to water. So ideally multiple troughs in the paddock that have really good flow to them. So the the trough never gets low because if your water can't keep up with the herd, then there'll be some cows that miss out. You know, the ones that get to the paddock first get the first shot, then the ones that come later, who are often the more subordinate cows. They're not left with quite as much water to drink. So some farmers will bring in an extra trough, same as what we do on wintering, to provide another source of water in the paddock. Obviously, make sure they're working on hot days. I always got in trouble if I hadn't checked the trough when I went to bring the cows in or when I went to shut them away. Another thing some farms do is have a trough at the shed or on the race somewhere, so that you know there's another opportunity for cows to. Drink. And then use the shade where it's available. So at Scott Farm, there's a an area of acacias, and I know of other farms that have similar stands of trees, and they use that as somewhere where the cows can go on hot days. You might have an off-paddock facility that has shade, which you can use. So trying to pick the paddocks or the areas of the farm that can provide the shade, sometimes topography, but not quite as effective as actual shade. Charlotte talked about one of the treatments in the trial being once-a-day milking. So that's working with timing. Often the afternoon is the hottest part of the day. So one way of dealing with that is to drop the afternoon milking. Another way of dealing with it is to shift milking to later in the day. Actually, one of the things that the trial will help us answer is a question that farmers have brought to us often is is it better to bring the cows in where the sprinklers, or is it better to drop that milking? So hopefully this trial will answer that question for us. The other thing you can do with timing is shifting feeding to cooler parts of the day when cows are actually, you know, they want to eat. When they're hot, one of the ways they reduce the kind of heat load is by eating less. So we can help them out by just feeding them in a cooler part of the day. And then, as I said, you can cool them at the at the shed. And Charlotte's done a really lovely job of explaining the two options there. Sprinklers or misters while they're waiting can really help kind of get rid of the heat load that they've taken on. And if you want to find out more about that, you can have a look at our DairyNZ website. There's resources already on there about all of those options. Obviously, we're gonna work on making them better and putting some more numbers in there, but there's certainly enough to get started.

SPEAKER_02 23:44

Great tips to help keep the cows a little cooler over summer. It's awesome to hear what we can do right now to help while we wait on a little bit more clarity from the research. It's been great to hear from you both. Thanks for those listening today. What's the key messages you would love them to walk away with?

SPEAKER_00 24:00

Lots of farmers are doing things already, and we already knew that, but they're often wondering if it's enough. And so that's what this research is about is we've heard from farmers that they want evidence before investing more. That's fair and that's what we're working on.

SPEAKER_01 24:15

Yeah. I think for me, as I sort of came into this project, DNZ does a lot of research that's forward-looking, that's for the future and setting us up for the future. And as I came into heat stress, I thought that was what we were doing here. That, you know, in a changing climate, heat stress will be a problem and we need to set ourselves up for it. But pretty quickly, looking at the data and hearing from farmers, the issue is now our farms are already experiencing a number of heat stress days. This is front of mind for a lot of farmers, and they are asking us for information and guidance here. So we are really keen to work with farmers to help us with the research that they need to support cow comfort through the summer.

Sprinklers Vs Misters Explained

SPEAKER_02 25:00

Charlotte, Jack, thanks for the update. This work is being shaped by what farmers like you have asked for. You told us you want clear evidence before investing in heat mitigation infrastructure, and that's exactly what this research aims to deliver. A practical business case for what works and what it costs. Whether you're already doing a lot, as Jack and Charlotte have both mentioned, and want to know if it's enough, or you're wondering if heat stress is significant enough on your farm to warrant action. The Scott Farm trial is underway right now to help answer those questions. In the meantime, if you're looking for practical tips on managing heat stress this summer, head to the DarianZ website where you'll find SummerSmart's resources. Thanks for tuning in to this episode of Talking Dairy. Make sure to hit follow so you can keep up to date with our latest podcasts. You can also stay up to date at DarianZ News on Facebook, Instagram, and LinkedIn, or go to our website and sign up for our fortnightly Dari and Z News emails. As always, if you have any feedback on this podcast or have some ideas for future topics or guests to have on the show, please email us at talkingdairy at DariNZ.co NZ. Jack, back over to you for the next Talking Dairy podcast. Catch you all next time.

SPEAKER_00 26:15

If you'd like to get connected with DairyNZ's latest advice, research, tools, and resources, whether it's reading, scrolling, listening, or in person, you can visit dairynz.co.nz forward slash get-connected, and don't forget to hit follow to keep up to date with our latest episodes. As always, if you have any feedback on this podcast or have some ideas for future topics or guests, please email us at talkingdairy at dairynz.co.nz. Thanks for listening and we'll catch you next time on Talking Dairy.