REX Recommends - Charlotte Reed

0:00This is a podcast from Rover. Rover? Rover will exchange with that speed. Outstanding in that field. All derriented scientists are in the final stages of an on-farm trial at its Scott Farm in the Waikato, looking at testing methods to reduce heat stress and see whether the investment is worth it for farmers that's called Comfortable Cows Outdoors Project. And to talk about it, we've got Dr. Charlotte Reed with us, a scientist at DerriNZ. Lovely to have you on, how are you? Yeah, good to be on. So tell me, where was the sort of the origin idea for this and were you involved with that? I was a bit. I've really inherited this project from another scientist but it's part of a three-year project that's designed to make sure farmers that are in a high-risk region for heat stress have the tools they need. And the trial we're running this summer is really part of filling the gaps to make sure we can provide that information. So when do cows start feeling heat stress

1:02and when does that impact on milk production? Do we know? Yeah, yeah, yeah. So cows have a lower thermo-neutral zone than us humans. So they typically feel comfortable between four to 20 degrees Celsius. So they will start getting uncomfortable as the temperature goes above that. And as it gets hotter, we see a number of behaviour and physiological changes. So there's other signs we might see before milk production starts to become impacted. And trying to determine the order of those responses and where milk production becomes impacted is still a big research question we're working on. Right, okay. So they show other physiological signs as it were and still trying to piece together, yeah, where the milk-sitter quality, you know, where one sort of ends in the other begins. Yeah, yeah. There's certainly some work in the past that we're building on that has started

2:03to look at where milk production is impacted. But the trick there is that study related to temperature and humidity. So just two factors of those conditions that a cow outdoor will experience, whereas where we've moved to now is looking at factors like solar radiation and wind speed as well. So as we build on that work, we need to bring in those factors to better understand, you know, what are the conditions that are going to impact on milk production and who is most susceptible from our dairy herd? So when we measure heat or define heat, are we talking about, as mentioned before, well, you mentioned both sort of internal and external. What's the, is it just temperature outside? How are you sort of ascertaining what heat is? Yeah. So how we measure heat stress risk in New Zealand is using the grazing heat load index. So internationally, a lot of places will use the temperature humidity index.

3:05And that's, so that's temperature and humidity. And that works really well in an indoor scenario. But because we've got cows outdoors grazing at pasture, we need to consider those other weather factors that will experience. So wind speed and solar radiation being the two big ones. So part of the work we've been involved in, alongside BSI and Fonterra, have been developing that grazing, grazing heat load index to bring those factors in to better understand, you know, how they are experiencing their environment and where the risk for, for heat stress is. Yeah, it's still a bit of work to do in that space as we develop it. But it's proving an effective tool so far. So you have question farmers across several regions. Are there, are there differences? I imagine it would be. Yeah, yeah, there are. So we have quite deliberately engaged with farmers in Bay of Plenty, Waikato and Canterbury.

4:07And that's because the modeling we've done using the GHLI, the grazing heat load index, says that those regions are at high risk for heat stress in the summer. So we've engaged with farmers through a phone survey, 350 farms, and there were some similarities and some differences. So it was quite reassuring that across all of those regions, farmers could tell us what they would expect to see if a cow was becoming uncomfortable in the heat, you know, bunching up, breathing heavily, reduced feed intake. So that was quite good. Farmers could tell us what they would see. But when we ask them how much of a problem is it for you on your farm, that's where we really saw some regional differences. So up here in the Waikato and Bay of Plenty, we saw farmers did rate it as a priority for them. They generally recognise it as some form of problem. And if it's not a problem, that's probably because they're actively mitigating it.

5:07That's what they told us. Whereas down in Canterbury, there were farmers who said it wasn't a problem because they're mitigating it. But there was a larger trunk than we saw in the Waikato who said, you know, it's not a problem because we don't think it gets hot enough on our farm. Which isn't in line with what the modelling says, but it was a bit of a regional difference we saw down there. So we're going to be doing some work with those farmers to see, you know, what are the signals do we see in the data that would either confirm that modelling or not? Interesting. And of course, as we said at the start as well, we've got the Scott Farm scenario as well with the research that's being done there. And it's quite interesting when I look through your sort of research methods, you've kind of got, it must be, you know, four or five or something sort of different sort of controls you might say for various aspects of the herd.

6:08So can you talk us through what those are and what you're actually testing? Yeah, so on the Scott Farm trial, we are looking at five hoods of cows held under different heat stress mitigations through the summer. And we're looking at the effect of those mitigations on their behaviour, their physiology and their milk production. So we have a herd that's gone once a day through the summer that's fairly common up here where farmers will just cut that afternoon milking. It saves them walking to the shed in the afternoon. So they're just on once a day through the summer. We then have two groups that are receiving a water-based mitigation at the shed. So one group is coming on to the afternoon yard and being held under sprinklers and the other is coming to be held under mistors. So again, very common and we heard a lot about these mitigations in our survey. We'll say the difference there with the sprinklers and the mistors. One is that larger droplet size of water designed to saturate the coat,

7:12whereas the mistors are much finer designed to cool the air around the cows. Then we have a group of cows where we are trying to show the effect of shade. So those cows are being held under shade throughout the day and then they're grazing with the rest of the cows at night. But they come onto the afternoon yard and they've got no mitigation at that point. They're on hot concrete. So it's sort of also looking at that daily pattern throughout the day and the timing of when the mitigation is applied. And then the last group we have is a control group who are having a hot summer. They are out on the paddock without trees and they have no mitigation on the afternoon yard either. So are there any indications given all of that, which of those methods is the most effective or more effective than others? Well that's really why we're trying to do this research. What's most effective might depend a bit on what each farm can do.

8:15It might be a bit individual. We often say there's a lot of value in shade and cutting out that solar radiation where that is a big driver of heat stress. But that's not true in necessarily every situation. So what we hope to do in this trial is to provide some information around all of these quite common mitigation so that farmers can look at that and look what would integrate best into their own business. Are there any early indications as to what might be more effective? And I know at all the courses, I understand what you're saying absolutely in the regions and all of that. But yeah, in general terms. Well, so we've finished data collection last week. So we've got a lot of data to get through. So one of our key outcome measures that we look at is respiration rate. So that's looking at the breathing rate of cows. We've done quite a lot of that over the last few years. And what we see is when cows become hot,

9:15they start breathing faster and faster in that rate increases. So during this trial, we looked at respiration rate out on the paddock in the heat of the day and then again on the yard in the afternoon. And I can probably speak to some preliminary results to that because that is our first thing that we've analysed and seen is that we generally see the shade group throughout the day. They're under shade. They have a lower slower respiration rate. So they're breathing slower. They're obviously not as heat stress as the other cows who are in unshaded paddocks. When we come onto the afternoon yard, we see quite a protective effect of those water mitigations on those two herds with them having very slow breathing rates at that point to show they're quite comfortable, whereas the control cows are hot at that point. But interestingly, we see the shaded cows, even though they're unmitigated on the yard, they're just on hot concrete.

10:17There seems to be a bit of a protective effect of not having that accumulated heat low through the day, whereas at that point, they're not breathing as quickly as our unmitigated controls. So there's certainly an effect of the different mitigations we're looking at there. And it seems like the effect of shade does have a protective effect even once they're out on the afternoon yard. Which is really interesting because often dairy farms, of course, don't have a lot of that because of pivot irrigation. So there's not a lot of option for that sort of thing. So that's an interesting... We are. Yeah, that's a regional difference we're kind of really got to be aware of. We are starting to see some farmers planting like the corners of paddocks and trees, like seeing that tradeoff of pasture has been worth it for the heat stress mitigation. But when you're thinking of heat stress mitigation, there's quite a bit to think about as to what's going to work best in your farm system.

11:21And in that case, there's options beyond what we're testing in this trial that may be effective. Yes, because it comes down to milk production, I suppose, as an end point. Do we know how much heat stress affects the production? We know it affects it. We can see quite clear signals in our data sets that at a certain point, you know, when the weather gets hot, we see a decline in milk production. But it's been quite a complex issue to tackle, simply because, you know, as it gets hot, you get pasture availability and quality declining at the same time. Cows get further into lactation and there's a natural decline. So we've got a lot of data, but it's been quite challenging to unpick what effect is purely due to the weather on the cow, rather than the weather on the feed. We have got a bit of a plan on how we're going to tackle this, because what we heard from farmers is that information is really key for them

12:22to understand what they're going to invest in. And in Canabria, it was quite key for them to see that evidence to determine if this is a priority for them. So we are planning a piece of work in the next few months, which is going to be looking at historical records of bulk milk and linking that with weather data over a number of years across the country. Just to get that big data set that's generalizable across the country, where do we see the signal for the effect of milk production? Yeah, that makes sense. That would seem, yeah, as you say, a sort of a bird's eye view almost of that. Yeah, yeah, yeah. Okay, that's interesting. What about trough location, water supply, the quality, that sort of thing of this? Yeah, absolutely key. You know, lactating cow can drink over 100 litres a day, and that demand is really important in summer. And when you have a pinch in the water in the afternoon on a hot day

13:22in the last cow to the paddock might not be catching up, it can have a real effect on their behaviour and their physiology. Yeah, definitely. Is there a creating as well, something of a regional temperature map? Is that right? We have got something like that. So there was a project a few years ago where we were using the grazing heat load index to model heat stress risk across the country, both now and then projecting in the future what it might look like, and that's where we determined, you know, where our high risk regions are. So that created a map on quite a fine grid to show, you know, canabry as a high risk region. Why cut it as a high risk region? Bay of plenty is one as well. We do have a few pieces planned to dig a bit deeper into some of that data, particularly where we get in canabry farm is not saying, you know, that's the modelling. It's not necessarily what we see on farm.

14:24So we've always got to, you know, be going back and making sure we're accounting for what we need to to accurately project risk. Yeah, it's going to ask you about the feedback from farmers. Obviously you've conducted that survey, but those that have actually visited your research facility at Scott Farm, what are they telling you? Oh, it was, yeah, it was a really positive day. I think farmers really appreciate being able to engage with the research and this group where people that have been involved in our heat stress research in some way over the last few years and some of them had been directly involved in the design of that trial. So it was really good for them to come and see what became of their involvement and a chance to connect with, you know, like-minded farmers. So it was really positive. We had some really good discussions about what we're doing. Farmers had some ideas for us about how we need to be communicating that information out as well as things that we could be testing

15:26in the future or options they would like more information on. There's always a limit to what we can achieve, you know, with the options we test. But we were also able to bring in some BSI researchers, so current results from BSI was there, and leverage some of the work they're doing as well. So a couple of farmers were interested in, you know, if you were planting trees for shade, what trees and how, and that's where we can leverage the work they're doing, integrating trees and livestock. Yeah, so it's multi-faceted by the sounds of things. You've got a lot of data that you've got to sort of get through now. Yeah. Big picture stuff, the more micro stuff. And, yeah, I suspect that, you know, that'll present its own set of challenges, but that's why you're collecting it in the first place. Is there any kind of surprise to you so far here, or is it just the data you've just got to go through it? Well, we do have to go through it. I mean, within the whole heat stress project that we've done,

16:29there's been a few things that have surprised me. I suppose the first thing is I'm originally from Northland, so quite familiar with the hot summers up there. But when we focused on our high risk regions, we noticed Northland wasn't actually one of them. And that was something that surprised me, because the modelling was showing that the coastal wind in Northland should be enough to prevent heat stress risk at that regional level, making it not necessarily a high risk region. But that's something that we're really going back and interrogating that data to make sure we've made the right call there, I'd say that surprised me and others in the project. Other than that, I think probably just the complexity of the milk production and heat load relationship and trying to untangle that feed data. When we came into this, we had 10 years of data from our research farm to look at that relationship.

17:32So we're fairly confident we could get somewhere, but we did, we saw a clear signal in the data, but it's very hard to pull apart, you know, they affect on the feed versus they affect on the cow. That seems to be the crux of the thing, doesn't it? Yeah, yeah, yeah, interesting. And I was surprised that Northland wasn't there, because you just assumed that it would be given the drought level that it seems to incur most summers, you know? Yeah, I mean, we do know that wind, particularly a coastal wind, is pretty protective against heat stress. But I think we do need to go back and make sure we are making the right call. Yeah, fascinating stuff. Thank you very much for the insight into all of that. That's really interesting. And I know that farmers are genuinely interested for obvious reasons in whatever comes out of it, whatever results you're able to turn up from the data. So watch the space, I suppose, but thank you. No, thank you very much. Room will exchange, with net speed, broadband for the land.