The Stomachs of a Ruminant

In this episode of the AK Podcast, host Mike Donaldson is joined by Dr. Luke Koester and Dr. Adrian Baker from Agri-King to explore the fascinating world of ruminants. They discuss the unique digestive system of ruminants, including the four compartments of their stomach, the crucial role of microbes in digestion, and the importance of forage quality. The conversation also touches on the innovative use of artificial rumen technology to analyze feed and improve livestock nutrition. The episode concludes with reflections on the significance of ruminants in agriculture and their ability to convert low-quality feed into valuable nutrients.

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Transcript

Chris Radke (00:01)
Hello and welcome to the AK Podcast where we explore science and nutrition behind livestock care and management with the best and the brightest in the business. I'm your host Chris Radke, part of the Sales Department here at Agri-King and with me today as usual is the Director of Field Service and a Member of the Sales Management Team, Mr. Mike Donaldson. Mike, how you doing buddy?

Mike Donaldson (00:22)
Very well, Chris. 2025's come in pretty good. Our first one of the new year.

Chris Radke (00:26)
Yeah, do you do any New Year's resolutions, Mike?

Mike Donaldson (00:31)
I stopped fooling myself a long time ago. just sorta try to do better and don't tie it to a certain date.

Chris Radke (00:38)
There you go. you win every time. You get that.

Mike Donaldson (00:41)
Well, yes,

you write them down so you do have to hold yourself accountable but you don't share them with people that are going to use it against you.

Chris Radke (00:51)
All right, Mike, what are we talking about today and who's with us?

Mike Donaldson (00:55)
Well we've got Dr. Luke Koester and Dr. Adrian Baker from Agri-King. We're going to go over what makes a ruminant a ruminant, I suppose. Some of the kind of special things about...

Ruminants that make them very different than monogastric like ourselves. Dr. Baker and Dr. Koester. Thank you so much for joining us. Luke, would you like to give a little background and then we'll go to Adrian for the same then we'll get on topic.

Dr. Lucas Koester (01:26)
I thought this was Adrian's show. I'm just tagging along.

hi. My name's Lucas Koester and I have my PhD in microbiology, focusing mostly on ruminant microbiology. So both the feed fraction as well as the epimerial communities of that rumen, which are adhered to the wall. So there's a plethora of organisms in there that are super interesting to me.

that just kind of took me on my track as a microbiologist and as an animal scientist, kind of both. So that's where I'm at today.

Mike Donaldson (02:06)
Perfect. Adrian, tell us a little bit about yourself, please.

Dr. Adrian Baker (02:11)
Yeah, got my PhD in animal science, focusing specifically on more on feedlot nutrition of the beef nutrition game. But yeah, you know, spent a lot of time working on starch utilization, whether it be corn processing or just looking at starch digestibility and feedlot cattle. So that's kind of my background. That's I would say that was most of the focus of my PhD.

Mike Donaldson (02:40)
Perfect. what are, mean, obviously, Agri-King's a nutrition company. We mostly are dealing with ruminants that are cattle, dairy or beef. But just to sort of set the field a little bit, what are some of the other animals that are actually classified as ruminants?

Dr. Lucas Koester (03:00)
Adrian, take it away.

Dr. Adrian Baker (03:01)
well, so Dr. Luke and I, were discussing this the other day and we kind of, you know, we both, I think, thought back to that, you know, when you get into these grad programs, they always have that like first day of class, right? And it's like, well, here's the, you know, the ruminants and here's what's going on and here's what are ruminants. And there's actually, there's ruminants. So that's your cattle, sheep, deer, bison things. And then there's

kind of a little subset called pseudoruminance and that falls into camels, llamas, and alpacas. And what makes them pseudo is they don't have an omasum where ruminants have four compartments of their stomach. They have a reticulum, rumen, then an omasum, and then an abomasum.

Mike Donaldson (03:47)
So when I've spent my whole life saying that cows have four stomachs, I've been wrong every time is what you're telling me.

Dr. Adrian Baker (03:55)
It's mostly generally assumed it's four compartments because it really takes the whole organ though you can actually technically remove the omasum That's been done experimentally and the animals still are able to digest feed. yeah, each compartment has a separate, I guess you'd say specialization that furthers the digestion for that animal.

Dr. Lucas Koester (04:05)
Bye.

Mike Donaldson (04:20)
Well, let's take, maybe walk us through in the order that feed would pass through those four compartments. You already named them off, but let's start with the reticulum. What's its purpose? What's it do? Just kind of go A to B to C to D through those areas, please.

Dr. Adrian Baker (04:44)
Yep.

Yeah, so the reticulum's kind of, you know, if you're thinking about the digestive tract as a highway, right, you know, if you look at a monogastric things flow down the esophagus, go to the stomach and then the small intestine. So ruminants are a touch different because you got the reticulum and that's, I would kind of, if you're looking at it as like a roadway, I would call it more as a roundabout.

Mike Donaldson (05:12)
Okay.

Dr. Lucas Koester (05:12)
Hahaha

Dr. Adrian Baker (05:13)
Feed enters

the reticulum and from there it has the ability of either going to the the omasum. So that's kind of really what most people classify as the third area, but that's not really what happens. It goes to the rumen. Then as part of that animal ruminates and they're contracting and breaking down those feed particles, some of that flow will end up back in the reticulum and then it'll flow to the omasum. And that omasum is kind of the...

almost like a barrier in that roundabout for particle size, essentially. And so it doesn't really go from reticulum to rumen and then omasum. Everything has to go back to the reticulum before it can go on. Is that a fair roundabout?

Dr. Lucas Koester (05:53)
And what,

that's a hilarious and pretty perfect description. What's the common name for the reticulum, right? Isn't it the hardware stomach is what they call that? Where you would put a magnet down there in case they got into something that they shouldn't or... And then when it comes to the rumen, I heard it best described as just a big...

Dr. Adrian Baker (06:01)
Hahaha

What?

Well...

Dr. Lucas Koester (06:23)
big fermentation vat, right? And stuff sits in there until it becomes small enough to flow. I like that roundabout analogy because it is kind of like there's actually a little speed bump, right? That initial contraction to get back over, back into that reticulum and then keep that flow going. I think that's, I'm going to use that one, I'm steal that one.

Mike Donaldson (06:49)
So, so when we get to, I mean, they're not called, we don't call cattle reticulites. They're not abomasomists or something. They're ruminants named after their rumen. You referenced that it's a kind of a big fermentation vat, Luke. What size in a in a mature dairy cow, I know steers are going to be a little bit different, but what size vat are we actually talking about?

Dr. Adrian Baker (07:02)
Mm-hmm.

Dr. Lucas Koester (07:16)
Yeah, I guess and Dr. Baker, you've probably done some cannulated animals experiments, but what I've found is I can fit the contents in a 40 gallon trash bag, 40 gallon trash can usually, but then, you know, it can, the way, the metrics I've heard is it can hold anywhere between 40 to 60 gallons in a full-sized animal. So, you know, it's quite the experience to like pull that amount of material out.

you know, do the research and then put it back in. You know, pretty interesting.

Mike Donaldson (07:51)
So when it does, we'll get back to a little bit more about rumen in a minute, but to continue that highway analogy, we've come back through our traffic circle. What's gonna go on, where's that feed going next?

Dr. Adrian Baker (08:09)
Okay, so from there,

the

Mike Donaldson (08:11)
HMM

Dr. Adrian Baker (08:12)
size is small enough, it'll flow to the omasum. And think of the omasum as kind of, it's a filter, right? It's made up of multiple layers of epithelial tissue, so then that way that digested will flow through that, and that's what's screening out big particles and letting small particles through. But the key point of why it's multiple layers is absorption.

So if you think about digesting the room and you're going to be, I don't know, what do you think, Dr. Luke? Three or four, maybe 5% dry matter, it's a lot of water.

Dr. Lucas Koester (08:53)
yeah, for sure. Yeah.

Dr. Adrian Baker (08:54)
And

so you got to suck that water out and that's what part of that omasum is that's why it has so many layers is to get that water out before it hits the abomasum or what most people call the true stomach, right? So if we think about ourselves the stomach is our stomach, you know is full of stomach acid, right? And obviously there's some proteases and things that occur in there as well but if you hit your your Acidic stomach full of all that water and you know, Dr. Luke just said

there's anywhere from 40 to 60 gallons of water in there theoretically, that's going to dilute your stomach acid down quite a bit. So you got to pull out that water before it hits that stomach acid so you can actually have the acid do what it needs to do and further break down that feedstuff.

Mike Donaldson (09:39)
Perfect. So now we're going to go into our fourth compartment, our fourth stomach, what you reference as a true stomach. What's happening there?

Dr. Adrian Baker (09:50)
Well, part of that acid, right? If you want to get wild and think about the structure of proteins with how they're balled up in their tertiary structures and all that jazz, those stomach acids at a low pH will actually straighten out those amino acids. Then that lets things like trypsin,

which should be like a proteolytic enzyme in the stomach come in and cleave off those amino acids. So then it'll be able to flow down into the small intestine for absorption. that, that the acidity, there's a couple of things that happen with acidity. You know, also part of it, like on, on our end, it helps kind of sterilize things. A lot of pathogenic bacteria, right? Dr. Luke are, are, are killed by that true acidity, but the big part from a digestibility standpoint, you're going to see on that protein side.

proteins are very, very susceptible to lower pHs, right? So they'll take away that structure of them.

Dr. Lucas Koester (10:55)
Yeah, the abomasum, that true stomach, right, that resembles ours is a pretty important screening tool for both myogastric and ruminants in that case where, you know you do have nutrients that need to be denatured like proteins and you have foreign particles getting in there, foreign living agents getting in there that could go into that hindgut, establish infection. So that's just another hurdle.

know, an innate hurdle that these microbes need to get through before they take over and cause

Mike Donaldson (11:36)
Well, circling back then to the Ruman, and I don't even remember where, who, what, but I've seen several presentations on this type of topic, and people seem to love to put up a picture of a bison or a white-tailed deer, something that is living on forage and nothing else type of thing, and say that in its purest form,

this animal has a rumen that lets it eat these really low quality feeds because then in her rumen these things can happen. We're working with the same layout, I understand that, but in either case, a high producing steer, a dairy cow, or a bison, what's in the rumen that's breaking this, that's breaking all the feed down, what's in the rumen that's letting her

Chuck you into alfalfa and corn silage in a way that my family doesn't want to.

Dr. Lucas Koester (12:42)
Well, some microbes, of course, right? They're the ones. They're the key players. Dr. Baker, I don't know. I can kind of take this one a little bit.

Mike Donaldson (12:43)
You

Dr. Adrian Baker (12:52)
You got it, you're the

Dr. Lucas Koester (12:54)
Yeah, it's definitely something that separates that foregut, that fermentation vat, those microbes that are housed there really separate the ability of these ruminants to degrade these.

cellulose from forages in a way that no other animals on the planet can. Yeah, I know termites. I know termites. Yeah, but mammals, let's say that, no other mammals can, right? So let's go there. But it's super neat because these are very specialized microbes that do this work. They require very specific conditions and

Mike Donaldson (13:21)
Yeah.

Dr. Lucas Koester (13:42)
The cow, the ruminant animal, provides those things, that being a specific temperature. So that body temperature that's regulated by that host is maintained. The host provides food by consuming it and getting it to those microbes. The host keeps it in anaerobic environment and provides enough water for all of that metabolism, all of that.

synthesis and things that happen there to take place. it's really like so, I guess to kind of put it in perspective, we're looking at, you know, we're looking at

probably tens of thousands of different species depending on what metrics you're using, whether that be using genomic technologies. Regardless, we've cultured, I think at this point, 500 to 1,000 different species, but we estimate many, many more. And they all come in varying abundances, so much so that they estimate an ounce of rumen fluid contains a trillion

bacterial cells, bacterial or micro cells, mostly bacterial. That's anywhere from 50 to 90 % of the total biomass in the rumen. But let's just take a trillion cells per ounce and there's how many ounces per gallon. I think I did a quick math on 40 gallons. I had to my calculator out, take my shoes off, do some counting. But yeah, it's like 5,000 ounces in 40 gallons of

Mike Donaldson (15:23)
Hahaha!

Dr. Adrian Baker (15:24)
Yeah.

Dr. Lucas Koester (15:29)
rumen content and so if you use that number you can expect in the quadrillions in the rumen total cells in there from all of these microbes and it's it's it's staggering to think about and another layer of that intricacy is that all of these microbes have to live together in this community and interact with one another and

are facilitated by the host. So as much as you think cows are silly little animal, silly big animal that hang out in the pasture and walk around and mosey all day, they've got quite the system going on in their gut. we're just scratching the surface on the research level. And so it's been really exciting to be a part of looking into that.

Mike Donaldson (16:23)
So it wouldn't be, it might not be completely accurate, but it would be close enough. We used to say something was close enough for government work. don't know if that's safe to say anymore, but

Dr. Lucas Koester (16:35)
Horseshoes and hand grenades.

Mike Donaldson (16:37)
you are. That when a cow is eating forages, she actually can't get any benefit out of those.

Chris Radke (16:37)
you

Mike Donaldson (16:51)
it's actually the rumen microbes that we're feeding and then she's getting her nutrition off of those rumen microbes.

Dr. Lucas Koester (17:00)
That's exactly right. And it's kind of like a weird analogy where we're as farmers, know, farming and raising these livestock up and then them themselves are kind of have their own herd of microbes in their gut that they're raising up and providing for. So in a way they're farmers too, right? So.

Mike Donaldson (17:14)
You

So

what you're telling me is even the biggest 10,000 cow dairy is an individual cow's keeping a lot more things alive than that guy with a 10,000 cow dairy.

Dr. Lucas Koester (17:28)
Yeah, feeding a quadrillion little microbes probably cuts a big check.

Mike Donaldson (17:37)
We hear people talk about forage quality. I'll be honest, think sometimes people want to ignore the wonder that is a ruminant and wish they were just monogastrics. And if we could feed them the way we do hogs or chickens, oh, it would be so simple and we're just going to pound grain. And I think that's a wasted opportunity.

Why is an animal able to get more out of higher quality forages? If she's got what it takes to break down fiber, why do we spend any time talking about the benefit that can come from forage quality?

Dr. Adrian Baker (18:21)
Well, I mean, the big part of it is there's really nothing that can... Well, I shouldn't say nothing. It is really, really challenging to digest lignin, right? And so as forages mature, they end up having more lignin. So I always kind of classically think of a tree bark and things like that, right? It's full lignin. So as forages, from as they grow, they...

Dr. Lucas Koester (18:21)
I'll let Dr. Baker take this one.

Dr. Adrian Baker (18:48)
put up more lignin, that's just part of their life cycle. But yeah, ruminants really struggle to ferment those. To my knowledge, Dr. Luke could probably say, yeah, that sounds right. You need aerobic respiration to really break down lignin.

Dr. Lucas Koester (19:04)
Right, yeah, it's brown rot and white rot, right? So, well, white rot, actually, technically. Mostly fungus, right? Mostly fungus, not even bacteria, so.

Mike Donaldson (19:07)
Ha

Dr. Adrian Baker (19:07)
Yeah. yeah.

So, in an anaerobic environment, you can't have that. so, no, I mean, when it comes to forage quality, the ruminants can do quite a bit, right? But what always comes into play, you know, on the dairy side, on the beef as well, is passage rate. And so, the longer it takes something to sit in the rumen,

the less that animal's gonna eat and the less that animal's gonna produce. So, I mean, think of it as energy going in and energy going out. If you've got a delay in there, there's not as much energy going out, right? So that's where, you know, when it comes to a lot of like high efficient or high productive animals, yeah, you gotta push a lot of good quality forages to keep that passage rate up, keep that digestion flowing.

and keep that animal eating. Because if they're not eating, they're not gaining, if they're not gaining, or if they're producing milk either, it's about kind of getting that throughput of feed intake. so speed of digestion is definitely essential.

Dr. Lucas Koester (20:19)
Yeah, that, mean, that to some degree is the same kind of ballpark idea of,

you call it, well, just improving your digestibility to get your feed to gain ratios. Like you want, you want that feed to be broken down as much as possible because I think that, you know, you would agree that the biggest bill on the farm is, is, feed costs, right? So, so maximize it and put those high quality forages in that are

Dr. Adrian Baker (20:36)
Thank

Mike Donaldson (20:43)
Mm-hmm. Mm-hmm.

Dr. Lucas Koester (20:48)
low lignin that the microbes can break down more rapidly and get the maximum amount of energy out of that in the time that it's there.

Dr. Adrian Baker (20:53)
Mm-hmm.

Mike Donaldson (20:59)
I know because he started a couple months before I did back in 93 that our former Vice President of R &D, Gbenga Ayangbile, one of the first things he did at Agri-King was to essentially create the only artificial rumens that have lived nonstop for the last 30 plus years now.

What does that mean as far as our ability to better value feeds? How are we analyzing? What are the things that you guys can use that technology to get at a jump? mean, obviously we don't do anything only in the artificial rumen But as far as narrowing down the possibilities before we do take it to the field, how are those artificial rumen is an asset to us?

Dr. Lucas Koester (21:54)
Yeah, so I think,

you know, I like working with those things. I also like working with real living rumen and content. There are some differences, absolutely. But the reality is by bringing those, let's say, that outside microbial community inside, we are basically controlling the environment that they are living in.

That allows us to cut down on lot of the variables or the variation that you would classically see in a herd of cattle. You don't have breed effects. You don't have environmental effects. You feed the same diet every day at the same time kind of thing. So you don't have these fluctuations or these random events that throw chaos into the mix.

By having that control, that structure, we can really have a really good way to compare feedstuffs and compare the digestibility of what we call ex vivo or rumen microbes that were taken from the rumen originally and then transplanted into these systems that we control.

We know generally that

that chaos has a really big impact on digestibility, on the utilization of that feedstock. by doing that, we

a number, a digestibility number, to an individual forage or individual nutrient or food feedstuff. And that helps us build rations. Would you agree, Dr. Baker?

Dr. Adrian Baker (23:48)
Yeah, mean, you said it perfectly, think. Variation. You know, there's quite a few studies where even they two steer side by side, emptied the rumen contents, they measured microbial populations and said, okay, well, know, steer one has 30% of this microbe family, right, or species, and then steer two has 40%, and they'll swap rumen contents.

and I believe it's about a week if I recall, you've read a lot of those studies too I assume before they returned to their original population. And so when you start trying to do like in situ work which a lot of people do in situ, I mean you can't use that same animal for year after year after year. And so when you start thinking like well two years ago we had really great milk output what is the difference between here and there? Well then so.

you've got potential variation in NDF digestibility number that you're getting along with, you know, obvious variation between year to year. And so by using those, we're taking out some of the variation.

Mike Donaldson (25:01)
Perfect.

You guys have given me a lot to think about. I'm sure other people are sort of in that same, still trying to get their head around the quadrillion little things being taken care of in that cow's room. Any closing thoughts or observations? I mean, you guys obviously are smart. You could be doing anything for a living and you choose to spend your professional life dealing with ruminants and rumens. Any final thoughts on that?

Dr. Lucas Koester (25:30)
Well, I guess we can bring up the number that

everybody talks about just to put it in perspective of the importance to animal production that ruminant in dairy animals, probably more specifically, but to some degree in beef. We can expect that the microbial activity in that rumen

degrading that feedstuff and basically creating fermentation end products or waste products that then the animal itself can absorb and utilize its energy, that process accounts for a lot of people say 70 to 80% of the entire energy requirements of that animal. so that to me says a lot, says that that

process of basically those microbes are mandatorily there. It's the way that these organisms will thrive, the host will thrive because the symbiosis between the microbial community that it's holding onto and the products that that microbial community makes in turn. So it's really a big impact for these animals and it's really

In my mind, I know people can say that they'll live without defaunated rumens and they'll be fine, but really you're not going to get the maximum production, you're not going to get maximum health without these microbes. really important.

Mike Donaldson (27:15)
Perfect. Adrian, any closing thoughts?

Dr. Adrian Baker (27:18)
Well, I would just keep in mind, you know, if you look at, you know, ruminants versus kind of some of the other animals involved in agriculture, you know, there is a lot, a lot of cellulose that gets...

pumped out there and the ruminants are, you know, they're essentially the waste bin of human food production. You look at like things like high fructose corn syrup and corn gluten coming off that. Yeah, can you feed those to monogastric? But will they fully be able to utilize all that fermentable fiber compared to a ruminant? You know, and then if you just look at our total land mass, you know, and even in the US, you know, so much of that ground isn't tillable.

A lot of in pasture, that's all that can be utilized for pasture. And so when you think about that cellulose mass that's coming off that pasture, needs to be utilized. And rumen is one of the only animals that can really utilize it.

Dr. Lucas Koester (28:19)
Yeah, absolutely. I completely agree.

Mike Donaldson (28:22)
I read

an observation over the weekend that said, so congratulations, you've decided to be a vegan for whatever strange reason. And you're not gonna drink soy milk, but one of the only things that comes close to making that really work is that we can feed the soy hulls that used to wrap that.

I'm sorry, almond milk, we can feed that almond hull to a ruminant to get more use out of. And the same with distillers grains that come off of ethanol. I mean, the amount, just what Adrian said, the amount of, you know, co-feeds, by-product feeds that we can then get more human nutrition out of by running them through ruminants would stagger people that have never given it any

Dr. Adrian Baker (28:55)
Yep.

Dr. Lucas Koester (29:16)
And that's another wild aspect I think too is, Adrian, you'll have to give me a number here. How many different feed stuffs do you think

Mike Donaldson (29:21)
Bang.

Dr. Lucas Koester (29:25)
fed in your day? Just, you know, it could be all kinds of things from, you know, almond holes to gummy bears to like,

Dr. Adrian Baker (29:26)
I don't know.

Dr. Lucas Koester (29:33)
know, and

rumen has to be able to adapt to that. And that's where those quadrillion microbes come into play. That's where those tens of thousands of species have.

basically all the metabolic capabilities that you could ask for in terms of harvesting energy. We did talk about lignin end being the challenge there, but it is really staggering to think about how adaptable that rumen has to be to, and that's not just the United States, it's all over the globe. What are those animals living on? What do they get day to day that they have to turn into?

you know, muscle mass or milk or something, you know, pretty wild.

Dr. Adrian Baker (30:18)
So.

Mike Donaldson (30:21)
Well guys, thank you very much. Chris, what did we learn today?

Chris Radke (30:25)
Hey, I am super fascinated with both these guys' passion. I said this before, it's oddities, but the fact that one of you guys said that it's a little community that's inside these animals and it's just walking around instead of just the cow that we see and the tens of millions of whatever cells that are working all the time complete with roundabouts.

know that. So that's what I learned today.

Alright, thank you so much for listening today. If you like what you heard, follow us on any of our socials. And if you have any questions or any comments that you'd like us to follow up on, you can hit us up at podcast@agriking.com. Alright, thank you very much, Dr. Luke, Dr. Adrian, and Mike. Thank you so much and have a great day.

Mike Donaldson (31:13)
Thank you doctors and thank you Chris so much. Everyone have a great day.