The effects of antibiotic use in livestock are far greater than the human health impacts of antimicrobial resistance. It is estimated that 90% of the antibiotics given to livestock end up in the soil. Despite these antibiotics no longer being detectable in manure they still significantly impact the soil microbiome. Research shows that these antibiotics reduce the ability of the soil to capture and store carbon, and the ability of soil to respond to increased temperatures. Livestock manure and the soil are breeding grounds for antibiotic resistant microbes increasing the potential impact on human health.
Dr Carl Wepking is a soil microbial ecologist who has been studying the effects of livestock antibiotics use on the soil microbiome. His research has focused on how livestock antibiotics reduce soil microbial activity, decrease microbes’ ability to adapt to high temperatures, and decrease the soil’s ability to sequester carbon. He also found that the effects of livestock antibiotics on the soil microbiome did not require detectable levels of antibiotics in manure. Carl is at the University of Wisconsin- Madison where he is running the Grasslands 2.0 program that aims to develop sustainable livestock farming systems.
I recently caught up with Carl to hear more about his work.
The effects of antibiotic use in livestock are far greater than the human health impacts of antimicrobial resistance. It is estimated that 90% of the antibiotics given to livestock end up in the soil. Despite these antibiotics no longer being detectable in manure they still significantly impact the soil microbiome. Research shows that these antibiotics reduce the ability of the soil to capture and store carbon, and the ability of soil to respond to increased temperatures. Livestock manure and the soil are breeding grounds for antibiotic resistant microbes increasing the potential impact on human health.
Dr Carl Wepking is a soil microbial ecologist who has been studying the effects of livestock antibiotics use on the soil microbiome. His research has focused on how livestock antibiotics reduce soil microbial activity, decrease microbes’ ability to adapt to high temperatures, and decrease the soil’s ability to sequester carbon. He also found that the effects of livestock antibiotics on the soil microbiome did not require detectable levels of antibiotics in manure. Carl is at the University of Wisconsin- Madison where he is running the Grasslands 2.0 program that aims to develop sustainable livestock farming systems.
I recently caught up with Carl to hear more about his work.
Carl Wepking Interview
AS
Okay. Welcome. Thank you very much for joining me. And if you just like to start by outlining, outlining what you've been doing in terms of your research and what your focus is.
CW
So, just in terms of antibiotic and and microbes question generally,
AS
more broadly more broadly as well, where the whole I'm interested in, not going down obviously there's a rabbit holes and you need to understand the the specifics of things and get into the details, but I'm also looking at the big picture as well. So you worked on the grasslands to project and it's a lot of what you're doing is focusing on how humans interact with soils through various different means and measures. And the effect that has on soils the effect that has on the environmental impact of our food systems, and then kind of we'll dig a bit deeper into the specifics of antibiotics and their impact, but it's a bit of a setting. That's what I was sort of thinking if that's cool with you.
CW
Yeah, so I'm the program manager for the aggressive 2.0 project. Which is a USDA funded, five year project focused on sort of creating a blueprint for what agriculture in the Upper Midwest could look like. And we're doing so with the lens of the ecosystems that used to exist in the upper Midwest. Which were sort of perennial prairies and grasslands, and bison and other large ruminants being pushed around either by indigenous peoples or wolves, or but some sort of rotation going on. So our big push is trying to simulate that on farms with rotational grazing and understanding there being those type of agricultural systems that were here before Western agriculture came in and and and went a different direction. But those systems were and them running for for hundreds of 1000s of years is why we have such rich soils and such great ecosystems to begin with. So trying to put together an agricultural system that can also provide more than just inexpensive food, but one that can actually provide healthy food for people to eat. healthy environments, healthy ecosystems, healthy communities and yeah, that's the that's the nutshell of the grassland 2.0 project. And when I say gone, was
I come to it from a soils background. But for me, it's you know, taking care of the soils is a part of that. That bigger picture of the of the whole system, but I must say that my really heavy focus on soils has taken a backseat to this larger like creating this blueprint question like the soils are at the heart of it, but the different levers all around that are, are taking more of the focus.
CW
So from what you're saying, I'm gathering it's it's very much looking at it from a systems approach and you could easily say there are three systems, the animals, the plants and the soil. There are many people who might throw in a fourth system in there, which would be the actual rumen microbiome which is a very vibrant and diverse biological entity in itself. So is the is the focus looking from your perspective because your backgrounds in microbiology, I believe in that and so you learn from that through that lens or a much broader lens and where do you see the microbiome coming into that?
CW
So I would say my my background is much more in I would go microbial ecology much more so than microbiology. We focus more on the effect of microbial communities as a whole as opposed to sort of kind of knew microbiology as more individual, smaller scale individual microbes and I kind of take the broader microbial ecology or ecosystem ecology perspective. And go back to the project. Yeah, that it takes you in a larger scale view of things we've got people focused on. We've got a policy team that's focused on what policies could be implemented or what policies could be phased out that would help transition towards a more sustainable agricultural system. We've got financial folks trying to figure out how to deal with things like the burden of debt that farmers are in at the moment within the current system. We've when we go out and interview farmers and talk to farmers that's one thing we hear pretty constantly as you know, I'd love to make a switch but if I went into the bank and told them I was gonna take the cows out of this brand new barn I just built that holds you know, X many 1000 cows and put them back on the pasture. They would tell me to get back to the barn and keep milking, you know, so trying to figure out how we can facilitate some of these transitions with financial tools. We've got a decision support tool team that's putting together some web based tools to either sit down with some of them look at more ecosystem scale, so sit down with maybe a local politician or some other decision maker on a regional scale and say, what are the levers we can pull and what would power that impact? Things like various ecosystem services, flooding, nutrient pollution and waterways, nutrient pollution and groundwater erosion? All these different things? And how can we manipulate ag landscapes and one of the different scenarios that come up with that? And then we also have one that's developed for farm scale where we can sit down with an individual farmer and pull up their farm on a digital map and say, Okay, what are you doing now and input all the different factors and see how profitable it is? What are the different ecosystem service metrics that come with that? And then let's try a few different other things. Have you ever thought about switching this field over here into a grazing land for your for your cows? How does that change this field compared to this field? And those kinds of things, and then more teams beyond that. Supply chains is another big one. But we're taking a much broader view of like, really the whole the human side the people side of the of the system?
AS
Because, obviously, you mentioned before that there were for 1000s of years or hundreds of 1000s of years, there were bison running around over hundreds of 1000s of acres, but that doesn't necessarily gel with our current systems of roads and fences and towns. Yeah,
CW
yeah. It's hard to go all the way back to that. But but going out to you know if you can do that, but on a farm and then moving them around, because the more we find these really great ecosystem service benefits only come with well managed grazing. If it's continuous grazing, where the cows just have access to the whole pasture all the time. The the results aren't as good because the cows don't do a good job of providing rest adequately to different areas. So the overgraze the good stuff and undergraze the bad stuff. And at the end of the day, you wind up with what we call in this part of the country. Like putting green and thistles that's all that's left is the grass has been munched down to just it's nubs and you've got Russian thistles over your head. Doesn't really do a very good system. But if you can move them around and make sure they're rotating, you get a nice, rich, healthy, diverse pasture. So
AS
there's you know, as you mentioned, the obvious benefits of the grazing systems in terms of the regeneration of the land, the recycling of nutrients. On the flip side, there are the benefits of the more modern systems back in the barn, as you mentioned, where you get the more reliable financial performance and profitability, you get much more reliable and consistent production but in terms of you know, the quantity as well as the quality and the time that product will actually be sold to market. Are you trying to cherry pick the best of both worlds and come up with hybrid approaches where you can get that benefit for the soil and the land, but also give the farmers the tools so that they can manage their productivity and find out other business the same data with that same resolution?
CW
Yeah, that's certainly a great point and something we've talked about it hasn't come up recently. But back when the project first got started, we had this debate about you know, does it have to be 100% grass fed, like is that the is that the benchmark because we do know that supplementing a grass fed diet with some amount of grain can really boost productivity and so maybe we can fine tune that and say, you know, 80 20 or you can find some kind of balance that's you're still managing the land very well. And you're also getting a small boost from from grain. But it's not something that we've really hammered home to, you know, we haven't we haven't really delved into that research question of like, well, okay, what is the sweet spot there? But that's certainly certainly worth thinking about. And from, from an economic perspective, there are a good number of economists within our group who have really focused on that, especially for dairy, the profitability side of things and we've got a good amount of research that shows a grass fed system is kind of the apex of profitability, because your feed costs are so low, that you can accept a pretty dramatic drop in yield and if you're, if yield is your word, and your concern, then by all means the grass fed systems not going to be for you. But if profitability is your concern from a from a farmer's perspective, then the evidence we've gotten shows the grass fed is actually dramatically better. And it's just instead of instead of paying for seed and feed throughout most of the year, you're you're letting the sunlight and the grass take care of it for you. And so your your input costs are reduced to almost nothing. Maybe you've got to reseed a pasture. Every couple of years or something, but you can accept a big drop in yield and still have improved profitability based on reduced input costs.
AS
That's that's that's some very enlightening so thanks for that.
CW
Oh, I should also add one more detail with that. Being out of Wisconsin, we've got a pretty big problem right now with actually overproduction in dairy. farmers aren't really able to make and this is why there's been a I don't know if this news is traveled around outside of our area, but there's been this huge decline in the number of dairy farms in the state. The fewer and fewer and the ones that are they're getting bigger and bigger. But the real problem is that with overproduction. The way they describe is, you know, when when times are good, you you buy more cows and try to make more milk and when times are bad, you also try to buy more cows and make more milk because you're trying to so it's it's kind of this positive feedback loop that doesn't that doesn't bode well for farmers and any time they've tried to put together like I can’t remember what they call it, where farmers can band together and agree. Okay, we're going to cap our production
AS
at cooperative marketing board type of thing
CW
And any effort to do that within the state has not been very successful. So this is another way to help lower the amount of milk that's been produced without harming farmers, by also giving them a better market for it.
AS
Okay, on on that note, yeah, the Midwest is is obviously Wisconsin is famous for its dairy but the Midwest is very famous for a huge amounts of corn and also very vast quantities of soy. Yeah. Is there discussions, plans, ideas around the reintroduction of grazing animals into those cropping systems? And if there are, what does that look like?
CW
Yeah, that's one thing that we are working on. And so as part of the group and one of the themes I didn't mention was what we call learning hubs, which are these really place specific conversations we're having with certain groups, and we've got five of them now going in Wisconsin, Minnesota, and the latest one is in Illinois, and each one of these individual locations has their own challenges. And their own problems that that community faces and we're trying to figure out okay, then how how to how would a perennial based system best suit you and your needs? And I'm bringing this up because the one in Illinois, which we're going to go visit in two days, then sort of kick off some conversations with them. There's barely any livestock left to even put back out onto the fields. Down in Illinois, it is almost entirely corn and soybeans and and mostly corn. And so it's going to be a much different conversation down there compared to up here in Wisconsin where we've got we've got the cattle it's, it's more about getting the cattle back out on the land. Down in Illinois, the cattle aren't even really there and there isn't really this deep, like passed down knowledge of working in livestock based system, it's just not how farmers view themselves down there. And so it's going to be an interesting, interesting conversation and a much different problem. And so our goal with these hubs is that we know it's not going to be a one size fits all. solution for all these different communities and all of the Upper Midwest, there's going to be variability. And so we're trying to see that variability on like a community scale. So that we can then say, so that it can scale up, you know, so that, you know, we've talked to this one group in Illinois and and maybe there's another group in Indiana after that, that has a lot more similarities with this group in Illinois, and we can say, Okay, here's what worked here, and maybe you guys can learn from from our efforts there. Whereas this group up in northern Minnesota is heavily focused on water quality from a tourism perspective, it's a big fishing recreation area. And they're worried that right now that the only the only agricultural systems that are up there are mostly livestock, mostly grazing systems, but they're worried that because the winds are starting to shift a little bit towards other types of agriculture, and they're just trying to sort of head that off and protect this best tourist hotspot. So very different places, very different problems that they're going going through and we're trying to sort of learn from the differences and the similarities.
AS
On that note, especially the Illinois side of things, if you if you look at the California almond industry, they have bees or there are bees that are required for pollination, but the almond farmers don't actually own the bees. They have contract bee farmers come in and move their bee herds around the state and around the orchards as necessary. Are there any discussions or conversations of similar types of models with grazing animals?
CW
Yeah, so there's our group we're affiliated with, and I think that this tool was actually put together by a couple different groups, but I'm not coming up with the name of it, they are even referring to it sort of colloquially as like Tinder for for for livestock farmers and for people that own land. And the whole idea is that you can log on and say, Okay, I've got all this land, but I don't have any livestock and I know that having livestock on here would actually be the best thing for it. And other people can say, Okay, I've got the livestock, but I don't have any land for them. And so trying to make these connections that benefit both parties. It’ll probably come to me in 15 minutes with the name of what the name of the tool is, but it's something that we kind of point people towards as a way to solve some of those problems of I've got the land but no livestock or I've got the livestock but I have no land. And while that might not work well for milking cows that can work well for dairy heifers that that don't need to get back to the barn every day. And for beef cattle and also small ruminants. We've got groups that are working on more goats and sheep, that kind of thing.
AS
That some that's great to That's great to hear about. As well, to dig a bit more back into your area of speciality speciality into microbial ecology. How do you see or just give us an overview of where you see that fitting into the different systems and, and where you see I guess the advantages and any shortcomings
CW
or Yeah. A couple different ways I like to think about it.
I guess on the broadest scale, you know, not within my specific research questions about antibiotic use and livestock and what that does, but on a much broader scale. We know that the way to one way to promote more diversity in soil communities, because we know that you know, microbes being kind of the foundation but then you've got to go up from there to mesofauna, macrofauna and the soils and all of those together is what promotes a good healthy functioning soil. But to make a shift from something like corn and soybeans, which is what we have now, and maybe you're incorporating a cover crop in the best, best case scenario, but a certain piece of land might only see three or four plants in in years and years and years. And so it's not getting a diversity of roots in the ground and symbiotic relationships between different plants and different microbes are all different So to go from what can be at worst described as monocultures into more and and he annual monocultures with you have living roots in the ground part of the year, the worst, the worst case scenario and best case scenario, year round if you've got cover crops going but to go from that to perennial biodiverse pastures is kind of night and day when it comes to well functioning soils and providing I like to refer to as like if you build it, they will come situation like you're, you're building all of the right scenarios for developing strong healthy soils and diverse soils in terms of both the microbes and macro life within the soil. So for me, it's a no brainer, but like if we tried to put together a proposal recently to look at the soil health metrics of one versus the other and do these transitions. It was the money we're looking for money to pay farmers to de risk of these transitions from annual systems to perennial pasture systems. And there was a soil health component and a big thing we kept thinking as well. I don't even know why we like this isn't even a research question. Like we'd know that this is going to be better. I guess we're just measuring how much better that but there's no there's no question. It's going to be better from a soil health perspective. I guess it's just how far it takes the needle is what we're asking. But so for me that's that's where I come to this grassland 2.0 project is understanding that it's developing a system that is more better suited to supporting life in the soil,
AS
a more diverse and vibrant soil microbiome essentially across aging bacteria, but as well as funghi and all sorts of other classes of spaces.
CW
Yeah, yeah. And then the fair antibiotic side of things is uh, you know, I like to like to talk about it's, it's a very interesting question from a human health perspective, in that I used to joke I still joke I'm doing it now. But if you would have asked me 3, 4, or 5 years ago, what's the biggest like human health crisis on the on the horizon? I would have said and I still tend to say antibiotic resistance. The pandemic has kind of showed me that maybe that wasn't quite right. But there are a lot of good arguments that the way we handle livestock is is leads makes us more susceptible to these types of outbreaks. Whether it be bacterial or viral. With it, the antibiotics side of things. When I go in to talk with farming groups, I you know, the human health side of it is huge. I don't like to downplay that aspect of it, but my research is really much more focused on the impact that antibiotics going into the soils has on the soil microbial processes, and how antibiotics just in that, in the same way that antibiotics can affect a bacterial infection on your skin. They can infect they can affect the bacteria in the soil. And I think the numbers show about 80% of all antibiotics in the US go to livestock. I think that that number might be a little outdated, and maybe that was as of 10 years ago at this point. But I imagined I imagined it's still pretty similar. And then of that, I think the high estimate was, you know, in the 90s percent of those antibiotics will end up in the soil, either active or as an active metabolite of the antibiotic itself. And so it's not outside the realm of possibility to imagine that antibiotics are given to livestock wind up in the soil in one way or another.
AS
Is that all classes of antibiotics including the Tylan’s and the ionophores and everything.
CW
You know, I'm not so sure about the split and I know it winds up being a global issue very quickly to in terms of the ability for antibiotic resistant bacteria to spread I know the even though certain types of antibiotics are banned from use in livestock in the US, and a lot are banned in Europe. They also continue to be used elsewhere and so long as they're continued to be used elsewhere from from a human health perspective or efficacy of antibiotics perspective. That winds up being really problematic, just in that because of that horizontal gene transfer capability of, of spreading antibiotic resistance genes. Using it anywhere in the globe. I mean we kind of see that with the viral spread of Coronavirus, but it's very easy for antibiotic resistance to spread.
AS
So if I understand you correctly, you're saying that the soil the issue is that one by having these antibiotics 90% of which go through the animals and end up in the soil. You're you're using the soil as a reservoir for breeding antibiotic resistant species, but you're also going to affect the the quality of the soil microbiome
CW
are Yeah, in the in the way I focus on it is you're affecting then how the soils work. And some of our research has shown that it's not even just the soils but you can also affect sort of the plant soil microbe relationship.
AS
Do you want to give me a bit of a background in terms of what those impacts are? How it works?
CW
Yeah. So the research that we did, focused on the use of two different antibiotics that are both used in mastitis prevention in dairy cattle. Interestingly, one is a bactericidal, antibiotic, sort of lyse bacterial cells, the other one's a bacteriostatic antibiotic, which essentially, halts a protein synthesis pathway that essentially leaves the cell dormant or inactive. And that winds up having sort of interesting functional effects on the on the soil and the microbes. The way I like to think about it is you know, if you're like a balloon, you're popping a balloon, but it's a balloon filled with nice yummy, easily accessible resources for the rest of the bacteria or fungi that are there. That's going to be different than if you just leave that baloon locked up and harder to access. So with the bactericidal antibiotics, you wind up kind of favoring it's counterintuitive, but you favor the resistant bacteria a bit more, because you're creating more easily accessible resources that bacteria tend to thrive on more so than fungi. And with the other one where you're sort of locking up these little balloons full of resources, it tends to favor fungi a bit more, informs a more recalcitrant system that the fungi tend to do a little bit better. And so interestingly, and then you also have community microbial community shifts within those two because one will affect more active microbes, the bactericidal antibiotic affects more active microbes, more so than bacteriostatic antibiotic. So, so the two things that we found with looking at those two antibiotics, one is that with that, especially the bactericidal antibiotic, it can drive increases in microbial activity, or a better way to think about it as reductions in microbial efficiency. Instead of bacteria having to do their regular day to day lives of bacteria. They've got to do that plus deal with an incoming antibiotic that's trying to destroy them. And that either comes with say you turn on efflux pumps so that when the antibiotic compound gets into your cell, you can pump it back out again. Or you can produce an enzyme that will break down the incoming antibiotic before it can get to you. But in either one of those situations, that is not like an energetically neutral activity that's going to cost you something to do that extra bit of work and the way we see that is with an increase in respiratory whatever makes you those situations that is not an energetically neutral activity, it's gonna cost you something to do that extra bit of work. And the way we've seen that is with an increase in respiration, that the, the microbes are working harder to instead of just yet instead of just do their day to day life, they're gonna do that plus deal with the antibiotic and so they're gonna respire more carbon and they're going to work through more soil carbon as a result.
AS
Okay, so that's why there's less soil carbon sequestration, because you're actually increasing the the work rate, the metabolic rate is the respiratory rate of the microbiome.
CW
And I should say too that, you know, we're measuring that by we do measure soil carbon, but the main way that we're inferring that is by increasing respiration within those within those sites that we've we've had these experiments going on. So I think part of his these are kind of shorter term studies. We would anticipate that over the long term, you would start to see these decreases in soil carbon, but in in looking at just the amount of respiration coming off, we're sort of inferrig that there won't be this long term differences. But so far, we haven't seen as strong of differences within soil carbon itself, just in just in the amount of soil carbon that's being respired off. Because it's a it's a much larger pool, the soil carbon than the amount that's being respired. So even though there's more being respired, it's not really causing, like a very measurable difference within the soil carbon pools
AS
and have you looked at the effects of ionophores on the soil microbiome?
CW
I have not. I'm not sure I get Google Alerts anytime somebody publishes a new work on antibiotics not Not to my knowledge, no.
AS
Where do you see this, this going forward. Next in terms of what researches is needed, and you know, one of the reasons antibiotics are so prevalent is because they're effective and whilst we can say it'd be great to not have antibiotics out there, they are highly effective and they have enabled a lot of increased food to be produced cheaply. So we where do you see this going forward?
CW
Yeah, the I mean, from my perspective on the ecosystem function side of that, because I feel like again, you can't talk about this stuff without the elephant in the room is the human health side of things, always. But that's not really the focus of my research. Other than, again, it's the elephant in the room. So it's hard not to mention it. But from the ecosystem side of things and from the ecosystem, functioning side of things, I think a better understanding of the more long term effects maybe like I said before, some of the research that we have done has shown these immediate impacts on on respiration, but the long term effect and what this looks like over time is just as important. We've got some new research that we're trying to get published now. Hopefully in the homestretch is looking at what historical antibiotic usage means for sort of climate change impacts going forward, sort of looking at how changes in temperature, if changes in temperature over time affect different soils based on whether or not they were exposed to manure from cattle that had or had not been given antibiotics. And we found that at low temperatures or moderate temperatures doesn't seem to they seem to behave similarly. But at higher temperatures, they start to diverge. Kind of indicating, but even though there might not seem to be big issues with soil microbes, at sort of ambient temperatures if you do have these extreme temperatures that can start to shift and start to show reveal that there were in fact underlying differences between these microbial communities and how they function.
AS
So that would be between a temperate and subtropical sort of climate zone or
CW
so we looked at we looked at a range of temperatures 15 degrees up to 30 degrees Celsius, Celsius Celsius. Yeah. And I think the implication there because it was over a shorter period of time, but you know, the way I look at it as if these have sort unseasonably warm temperatures for a while you'll have these you'll have these shifts that can be taking place, you know, if you have a hot dry spell where the soils are hitting some extreme temperatures. You might see that the soils that have been given one type of manure will behave differently than ones that have been given a different type of manure based on whether or not livestock and they're given antibiotics.
AS
And what what's the differences in behavior of the soils that you observe?
CW
So the for the ones that have not been given antibiotics the microbes seem to be able to what's the best way to put it when they have been given antibiotics, the microbe seem inhibited at a high temperature at a high temperature with you know, you can imagine more resource being available we maintain moisture throughout so that there wasn't an interaction of moisture and and temperature going on. We tried to hold that as steady as possible. Both increase in temperature the bacterial community microbial community in the soils that had not been given antibiotic kind of explode, the microbial activity really skyrockets whereas the ones that had been given an antibiotic, it kind of plateaus at a high temperature. So the way I think about it is the the antibiotic seem to be, well the legacy effect of those antibiotics has created a community that isn't as well adapted to sort of take advantage of those high availability of resources that come with increasing temperature. And so the higher temperatures you can imagine because a lot of how microbes access resources in the soil is through extracellular enzymes. And with increasing temperature enzymes can be more effective or they can get into a better optimal range at warmer temperatures.
AS
So that's looking at how how they cycle nutrients and which will then make those nutrients available to the plants. That would if the nutrients are coming out of the soil then that would you could potentially conclude that you need less synthetic fertilizer because you're you're utilizing what's already there.
CW
Yeah, another interesting side of the fertilizer question. One of the studies we did previously looked at how carbon and nitrogen moved through the systems based on whether or not system ever been exposed to one or two different types of antibodies, manures from cows given antibiotics. And in one we found that plants were actually taking up more nitrogen out of the soil than when exposed to manure from cows given an antibiotic plants are able to take up more nitrogen from the soil than ones that had not been exposed to manure from cows given an antibiotic. So control versus antibiotic in essence. But interestingly with that you think like oh, is this a good thing? Is this growth promoting in that it's it's causing this uptake in in nitrogen from the soil. But we did not find that to be the case. We didn't see any difference in plant growth between these these plots. It seemed to be because in those ones where they were the plants were taking up more nitrogen, they were also losing more carbon. So it seems to be more that trade off of photosynthesizing carbon turning into sugar and then the plant funneling that down to the soil. Plants are shown to do that if they're missing some key nutrients like nitrogen like phosphorus or micronutrients as well, to try to stimulate the microbial community in the soil to go find what they need, or to go help them access the resources that they need. And so it seems like that trade off between carbon and nitrogen winds up as sort of a net neutral so even though they are taking up more nitrogen from the soil we're not seeing a difference in plant growth
AS
Have you ever looked at the interaction between the the soil microbiome and the actual ruminant microbiome?
CW
I have not that there were some researchers that we collaborated with out of Virginia Tech that that were looking at the rumen microbiome and then how that impacts the soil microbiome. And I can't, I can't really I don't have their work too fresh off the top of my head. The one thing I find interesting, we actually don't for one of them, we don't detect the antibiotic at all within the manure itself. You know, the two antibiotics we looked at, it was below detection and for the other one that was extremely, extremely low. But we still see the sort of anticipated ecosystem level effects of those two different antibiotics even though we can't really find the antibiotic itself. So there is some thought that it's not so much the antibiotic going into the system that's causing these differences. As much as it's the effect of the antibiotic on the microbial community within the within the manure within the rumen microbiome, that going into the soil that's driving the differences. And that's actually that's another interesting avenue for research is trying to disentangle whether or not because it could also be that the reason we're not detecting the antibiotic, but we're still seeing the effect of is that it's a metabolite that we're we're not able to detect the antibiotic itself. But if it's broken down into two pieces, you know, we're not we're not seeing those two pieces together, but they could both still be active, causing an antibiotic type effect within the system, even though we're not seeing the antibiotic itself.
AS
That's, that's netting and and the way the world works, where it's all about testing and identifying if you've got no detectable levels, but you still have impact. That means that it's it's it's harder to, to work with.
CW
Yeah, yeah. And for us those seem to be the two best explanations because you've, again, I like to sort of anthropomorphize microbes, but like you've you've stressed out the one option is you've stressed out the microbial community in the gut to the point where, when they wind the wind up in the soil they come in kicking and screaming and saying, We're all under attack, the sky is falling, we're all gonna die. The bacteria in the soil here that get the signals from that from the microbes, and beside, oh, okay, I guess we should all be stressed out and work really hard to get rid of any incoming antibiotic, but maybe the antibiotic isn't even there. Maybe they're maybe they're just stressed out because they're picking up on signals from the microbes that are coming in. And then the other option is the antibiotic is there. It's just as a metabolite, and harder to detect.
AS
That is absolutely fascinating, because have you heard of the concept hormesis?
It's so it's it's when organisms through various not really well known mechanisms can read their environment. So from a human health perspective, when you eat stress plants it seems to stimulate parts of your body that a protective or protective genes. That's essentially the evolutionary concept is that the earlier you can understand that you're likely to be under a system of stress, the more ideally you can adapt and protect your body against it and the more likely you will survive whatever that stress event is. It's led to the belief that there are various small molecules or other communication molecules in in the plants produce or certain organisms produce when they're stressed, and then other organisms can detect those. And this is a what you said there was something along that same concept on a microbial level. So I guess I guess this is an area that needs quite a bit of extra research, but by stressing I guess the, the hypothesis was by stressing the rumen microbiome, the microbes that pass through the animal will then subsequently stress the soil microbiome through these unknown communication pathways
CW
I do know there's a growing body of research on sort of how microbes communicate with each other through things like quorum sensing and quorum quenching molecules that get passed within. So quorum sensing If bacteria can sense that they've got enough cells around to carry out an activity that would have been sort of density dependent, but it wouldn't be an activity that'd be useful to do it if you were just the one cell working on your own. But if you can sense that around you you've got quorum. You've got a good amount of microbes there. You can then once it hits a critical mass you can switch on and carry out some activity that would be beneficial for for all. And I think there's some thought that there are certain antibiotic compounds that actually function that way that there actually can have an inhibitory effect on some bacteria, but they're also used as a quorum sensing compound. And I think that's one of the explanations for how antibiotics developed within the soil to begin with, or within microbial communities to begin with was as communication
AS
is the you've talked about the effect of the antibiotics coming through the animal into the soil on to the soil, and what's the longevity of that effect? is how long does it take for the antibiotics to to break down in the soil and the effect to be be no longer there?
CW
Yeah, that's an interesting that's an interesting question. The the work we did sought to not so much see how it say you expose the soil to manure from a cow given an antibiotic and then leave it alone, and see how long it takes to sort of rebound back to or just to see what trajectory it goes on afterwards. That wasn't the direction that our research went in. But certainly, this is one of those is going up or coming up through graduate school in like an ecology focus. You realize kind of quickly and it's a good it's a good discussion question. But funding cycles have a very clear impact of the type of research that gets done with the exception of like some like really good long term ecological studies and things like that. But like you're kind of limited to this like three to five year snapshot. And as I was leaving the project, it definitely crossed my mind like, Oh, someone should just keep sampling this for the next like 10 years. Like somebody should just keep coming back and seeing okay, we stopped we stopped adding manure antibiotics. What does it look like a year down the road? What does it look like five years down the road was it look like 10 years down the road? And I think that would be great research to do. Our work more sought to see with continued exposure to antibiotics. Does the system eventually level off? But I mean, does it that essentially does the system get so used to this antibiotic coming in that that's the new normal that's the new status quo. And that was part of that temperature manipulation experiment we did to try to figure out okay, they've been exposed to antibiotics, continuously for 32 months, monthly manure additions for 32 months. Then what happens when you cut them off on these different temperatures? And we still see differences even though with ambient temperature and they seem to function about the same. And so that was for us that was interesting to see that, you know, they didn't acclimate to it after 32 months of of continued exposure to it. It seems like it either caused enough of a difference or beyond that that maintained or that there wasn't really this adaptation taking place or if it was, it was superficial.
AS
And what's what's, what's next in terms of your research, and I guess, ways of implementing the results of that going forward?
CW
I think it's all to me, this is part of why I've kind of pivoted towards working with this grassland 2.0 project is that I do see that the use of antibiotics as problematic from an ecosystem perspective, but very much more problematic from a public health perspective. And any way that we can decrease the need for the use of antibiotics say by reducing the density, livestock density that is benefited from the use of antibiotics. So trying to get more more farms, less concentrated livestock trying to develop agricultural systems that move in that direction. To me, is that the next step for it so it's not so much the antibiotic specific investigations, although I think we've talked about there are a couple different a couple great questions. That somebody could ask within that within that about what is the long term ramifications once antibiotics have stopped flowing into the system and all of those would be would be great to ask. But my work has now pivoted much more towards okay, how do we develop agricultural systems that are less dependent on antibiotic use? And again, like you said, Not no antibiotic use and it just needs to be less antibiotic use more appropriate antibiotic use, as needed, as opposed to prophylactic? I think more decentralized agricultural systems would function better from from that perspective as well.
AS
And you I imagine you speak to quite a few farmers with the work you're currently doing, how did they take those points and those ideas or concepts?
CW
I think soil carbon, gets people's attention, much more so now than maybe it did 5 10 years ago. I feel like soil carbon is such a hot topic at the moment given the development of carbon markets and things like that, that farmers tend to resonate with those with those ideas, you know, that and I like to talk about to. I’m just talking about one little land management decision or one little farming management decision whether or not to give a cow an antibiotic. But even that little decision can have repercussions on how your system functions or how your farm functions. And so when I talk with that, by talk with this topic, about this topic with farmers, I like to start with, you know, this is about antibiotics, but it's not it's about land management generally. And the idea that there are so many different levers you have at your disposal, and each one of them can have effects that are unintended on your farm and trying to understand all of those can be overwhelming, but here's just one of them. And then here's the effects that we see based on this one management decision. And because a lot of what we're talking about now with the grassland 2.0 project is about trying to de risk and encourage different land management practices and different farming practices. So trying to get farmers to think about different possibilities, different options and how they all can have sort of different ecosystem level impact.
AS
Excellent well, thank you very much for your time, mate. Is there is there anything else that you think we should discuss today? We haven't so far covered?
CW
Not that I can think of. Have you said that this was for a piece that you're working on or what was the intended use of all this?
AS
So there's there's no pay to be like a podcast, I might put it up on it as an audio podcast, as well as a summary piece, which will be like a blog, a blog piece. So I'm, I think there are a lot of these issues that are being the sort of somewhere out there in the public domain, but they're not being discussed in as much depth and resolution people. I think one of the things people tend to have these black and white ideas about so many different things, and be that the current geopolitics, the current war in Ukraine through to climate change through to how animals shouldn't be raised. And I think the interesting part of where the value is, is all the gray in between, and it's bringing people who, who and having discussions with people who have knowledge of these areas and interesting and creative potential solutions. So just to create those discussions and create that awareness and sharing that within the sort of the community that we're working with.
CW
I appreciate that but that's great. Great way to think about things. And even from like the grass 2.0 perspective, you know, the interest of being gray areas. You mentioned earlier that the current model is really good at producing calories, you know, that the current model is really good at being efficient and efficiency is often what is what is touted you know we can get more from a dairy perspective, we can get more gallons of milk out of out of a Holstein than we could 50 years ago and we can do it really efficiently. And so, the elephant in the room is always where's the where's that sweet spot of? We're getting enough food to feed everybody. And we're doing so without doing too much damage to the environment in an ideal situation, but not damaging the environment. But can we find that sweet spot of feeding everyone healthy, nutritious food and at least holding the environment neutral as opposed to heavily damaging it? And you know, that's that's the that's the sweet spot where we're trying to figure out
AS
completely completely. And I guess one of the other motivations for the for doing this as that. You know, I'm very fortunate I get to speak to a lot of people here, like you and others. And I've had some fascinating conversations and learned a hell of a lot so it's trying to share, share that knowledge and those insights more broadly. And think back to what you said earlier about the one of the one of the shortcomings of the modern food system is that it's been so successful at producing lots of calories very efficiently, which means it's much cheaper. Something's very successful doing one thing, it's much harder to change it because you've got to backpedal more. And the flip side of that is we've created these one way systems you've got nutrients that come from our soils, they get grown into grains or to crops or eaten byanimals, they get put on trucks and they go to cities and then they get eaten and then they get pumped out to see generally so in 50 or 100 or 500 million years, you know, outside of New York City in the area outside London, there's going to be some monumentally fertile and Yangtze river areas but that’s in 50 or 100 million years when the geological activity is uplifted them and turn it back into soils.
CW
In the meantime, we have what's going on in the Gulf of Mexico, which and there's some really interesting relationships being built there to try to get shrimp farmers down in Louisiana to come up and speak to farmers in the Midwest and have the farmers in the Midwest go down and spend a week with some shrimp farmers in Louisiana and see how the two are connected. That better land management up in the upper Midwest the Mississippi Basin can improve the livelihoods of these shrimp farmers and anybody who's relying on the Gulf of Mexico fisheries for for a living. And yeah, it's all it's all related. And that's there's another speaking of you know, it's one way one of the colleagues I work with likes to refer to the current type of agriculture as essentially it's more like mining than it is anything else. And I think that's a interesting way to think about it as well
AS
as extractive industry rather than a circular industry.
Yeah, yeah. Okay, well, thank you. Very much. Once again, mate it's been an absolute pleasure speaking with you. So thank you for time.
And one thing, you know, probably by the time I get around to putting everything together, it's probably be a week or two with what's going on, but when it's ready, if there's anyone if a one thing if I get a picture of you or something like that, so we could stick that up on on when we put it up on on the website. And the other thing if there's anyone within your grassland 2.0 or within the university from their comms or media area that I could just collaborate with. So when when it goes out, it goes out to all of your network as well as all of our network. Sounds great. Okay. Cheers, mate. Well, you enjoy the rest of the day. Thank you very much. Thanks for the invite. Cheers. Thank you.
Transcribed by https://otter.ai