Feeding Practices to Prevent Subacute Ruminal Acidosis

- So I suppose we are on the top of the hour and we can start today's webinar.

Just a few things, housekeeping things.

I would like to remind people that this webinar is recorded and I'll be sending links to all participants, you know after the recording is edited.

Also, attendees can use the Q&A box for questions, and Dr. Vanson is gonna reply to those question either as it goes or after the webinar.

And on the end of the webinar you will see again popup questionnaire or survey on your screen.

So if you can take five to 10 minutes of your time, we would truly appreciate it.

We would like to know, you know your opinions and your directions in the future.

So now I would like to introduce our today's speakers.

Same for the last four webinars we have Vanson, and we are very obliged to him to do, you know these webinars.

Dr. Vanson is a professor and extension veterinarian at the Department of Veterinary and Biomedical Sciences at Penn State University.

He earned his DVM degree at Michigan State and PhD at Cornell University is research and extension interest focus on transition cow metabolism, metabolic diseases under prevention.

And today, as I said, last of the five webinars we were offering to our audience.

Dr. Vanson is going to discuss the prevention of luminal acidosis (indistinct) there comes, Robert please.

- Alright, thank you Michael.

Good morning, day, evening, early morning.

I know we've had quite an extensive showing from our international colleagues, so welcome and glad to be here yet again and provide some additional information on managing our transition cows and trying to minimize some of the disease consequences that we have associated with them.

So Michael's already given you my background and many of you from what I'm seeing on the participant list have been here at least once before, so I won't spend any more time introducing myself.

You may wonder how a veterinarian got involved deeply in nutrition and that stemmed from my private veterinary practice and academic practice where working with clients, I realized very quickly that veterinary school taught me how to take care of sick and diseased animals, but it really didn't do the job that it needed to in terms of preventing animals from becoming diseased or sick.

And that's essentially what the clientele, you know nobody wants their animals to be sick.

We know that the negative consequences of disease.

And so we really need to focus on the preventative side and that's what motivated me to get into the nutrition side and I think it's worked very well in communicating these kind of things.

So let's go ahead and get started here by outline for today, I wanna talk a little bit about ruminal acidosis.

I'm sure I don't really need to go into gory details about this, but I do wanna separate out and define SARA, which we know as subacute ruminal acidosis, and then really get into the meat of things in terms of defining the two key characters.

One is the dietary starch or fermentable carbohydrate load versus the dietary fiber.

And it's really the interaction between these two components of the diet that ultimately dictate the outcome and the health of the rumen.

And of course our interest is to maintain a healthy rumen with good active fermentation.

We can never separate the diet from other factors.

You know, the diet doesn't magically show up for the cows and so there's humans involved in preparing the diet and sometimes things don't get done correctly or timely.

There's also environmental factors, just space and social interactions and heat stress and so on.

So we'll talk just briefly about those kind of contributors to that could basically upset generally good diet.

And then what I'm gonna try and do in the summary recommendations is show you the progression over time.

I was commenting on this with Michael prior to the webinar in my researching and going back and looking at the data, you know there's been some basic recommendations, but as we've improved our understanding of rumen fermentation and analysis of dietary fiber, things have been modified slightly and so I want to kind of show that progression.

Alright, so let's get started with the basics.

What's ruminal acidosis?

Well, this is very easily defined as just a pathologic, meaning there's specific lesions that are associated with a disease process, it's a pathologic accumulation of acid in the rumen and this is a result of either excess fermentable carbohydrate intake.

This is the acid production or inadequate or overwhelmed buffering system.

The natural buffering system as we know, is the production of saliva, copious amounts of saliva that a cow will generate, but that saliva is generated in response to chewing activity, and that's where we get into the fiber side of things.

What happens here is we get a dramatic drop in ruminal pH that will adversely affect the microbial populations and ultimately alter fermentation patterns and so we often see a reduction in cellulolytic activity, so fiber digestibility goes down.

We know that the cellulolytic bugs don't perform their functions very well in a pH below six, so our goal is to try and keep that pH at six or slightly above.

We also know that there's a reduction in proteolytic activity in the rumen.

So that may either even further compromise some of the cellulolytic activity, because we know the cellulolytic bugs require ammonia as their primary nitrogen source.

And then of course, if we overwhelm the system, even though lactate utilizers, these microbes that convert lactate to pyruvate can utilize lactate, this strong acid, they are like cellulolytic bugs, somewhat sensitive to pH.

So let's look at this scenario here and look at the contributors to this problem.

So one, we have the buffering capacity of the rumen system.

This is, as I mentioned, a function of the level of effective fiber in the diet.

Now I use that word effective with some trepidation because the terminology has changed some.

But let's just say the fiber component that allows for chewing and saliva production as well as any dietary buffers that we may add.

I mean, most dairy cow diets will provide some additional bicarb or Mag-Ox to help with the buffering system that then has to be balanced with the rate of acid production and this is a function of the level of concentrate or grains that are in the diet.

Now, the volatile fatty acids, which are the primary end products of fermentation by the microbes, these are, as their name implies, they're all acids.

However, the three primary volatile fatty acids that we focus on in terms of their contribution to the metabolism of the cow acetic, proprionic and butyric are not chemically very strong acids.

They have what we call a pKa, if you remember, back to your basic inorganic chemistry that really they're not highly dissociated.

However, if under the conditions of the fermentation system, usually due to the excess presence of sugars and starches, we're now promoting what we call the non-structural carbohydrate fermenting bacteria.

And these bacteria try to out compete the other bacteria in the rumen generating, and they do that by generating this compound lactate, which is a much stronger acid and will be dissociated and that will result in a drop in pH.

Then the other side of this, the third component here is the rate of acid absorption.

So the pillae of the rumen absorb these volatile fatty acids and the more the acids you take away the lesser of the pH load or the acid load and so this absorption process is a function of rumen papillae health.

And I'm emphasize that because if we have repeated bouts of acidosis, we can actually damage the papilla and reduce their functionality or their surface area.

And also rumen pH, rumen pH is gonna dictate whether or not these volatile fatty acids can be absorbed.

Now there is some fairly recent research from investigator up in Canada, Dr. Greg Penner, where they're looking at bicarb independent pathways for absorption.

Most of the absorption is kind of dependent on the presence of bicarb.

And this may help minimize acidosis and what they're trying to determine is whether or not this is a genetic thing.

So this might explain why different cows are more sensitive to acidosis than others, or if it's something that could be dietarily modified.

So when we think about acidosis as a disease, like many diseases, it's really a continuum.

And the continuum here is the change in rumen pH.

So normally rumen pH should be in the six five to six range to facilitate good fiber digestion.

And as this pH drops due to the acid accumulation, we start to see some changes.

One of the first changes is lower milk fat, because with the lower pH, especially if there is a fair amount of polyunsaturated fatty acids in the diet, we can get conjugated linoleic acid that can suppress fat production by the mammary gland and this results in low milk fat syndrome.

We may see diarrhea more often.

I anticipate in a group of cows variability in the manure.

So I may have some loose manure and kind of intermediate and then we also may see some increased lameness, sole abscess issues.

As that PH goes lower, now we start to get into some more serious problems of, you know ataxia.

The animal can become depressed, they go down, become recumbent, they can get severely dehydrated, then they can go into lateral recumbency and become comatose and then get into a severe metabolic acidosis.

And so this is just the continuum of clinical signs that we can see due to acid load increasing in the rumen, the disease syndromes that are associated with this, as we call this intermediate or early stage of acidosis, subacute ruminal acidosis.

And then you start to get below a pH of five, then that gets into a more acute acidosis.

And then of course if you get very rapid drop in pH like in feedlot rations and things like that, then we could actually have an a peracute acidosis where you just find the animals dead from overnight feeding.

So this is the range in scenario that we can see with disturbances of the rumen system based on pH, we're gonna focus of course on subclinical ruminal acidosis.

Now why is acidosis such a problem other than you know the rumen health?

If we look on the left hand side of the slide here, this is structure of the papilla, normal structure of the papilla, the rumen.

You can see these leaf kind of extensions from the rumen wall and these have blood vessels in them and these will be absorbing those volatile fatty acids.

However, in acidotic conditions we can see matting of these papilla and damage to these papilla and then of course they can recover from this process.

But what's gonna happen is these papilla don't redevelop, they will remain scarred as this tissue here and that's gonna reduce the ability to absorb the volatile fatty acids in future insults and lead to that animal being more prone to acidosis even in a lesser dietary situation.

Along with this kind of changes to the papilla, we can actually see ulcers in the wall of the rumen with fibrosis replacing that.

So here's two scenarios of fairly extensive fibrosis of the rumen wall and lack of papillae.

And again, this is gonna reduce the ability of absorption.

And so we remove that third component to this.

When we get the damage to the rumen wall, we can get what's called translocation of the bacteria within the rumen.

And there's particular bacterial species that are most problematic and they get into the blood, the portal system, this blood then drains into the liver and then we can see things of abscesses.

This is typically anaerobic kind of situations or anaerobic bacteria, fusobacterium, necrofrom.

And these are really problematic in, and especially here in the US in our feedlot operations where we're feeding extremely high corn based diets.

Alright, so subacute ruminal acidosis, as I showed previously, is a much more insidious to chronic disease process.

The rumen pH is gonna drop below six, but usually remain above five or 5.5.

How subacute ruminal acidosis gets defined in the research studies that are published varies by the study.

Some use the threshold of 5.8, some use a threshold of 5.6, some use a threshold of 5.5, right?

I mean that's just nuance there.

Really what's more important is the total time that the rumen and pH stays below some particular threshold.

Now, the clinical signs that we typically associate with SARA subacute ruminal acidosis is recognizing cyclic intake.

One day you may have to feed 120% of what you would normally put into the diet or put into the feed bunk for that group.

Then the very next day they don't eat near as much and you drop that back and we often call this sort of slug feeding behaviors where the cows will really, they'll engorge, they'll get acidotic, they'll back off their feed for a period of time, but then they're really hungry and they come back and they do it all over again.

We also may see pica what this is is abnormal eating behaviors where they'll eat soil bedding and some people put out a free choice bicarb to kind of get a sense of whether or not the animal is looking for, you know some kind of remediation of their digestive upset.

As I mentioned, we'll see variability in the manure scores.

We may or may not see diarrhea, we don't always see diarrhea.

Diarrhea probably is more associated with hindgut acidosis more than the ruminal acidosis.

we see altered rumen function or fermentation, as I mentioned, milk fat depression.

These animals generally will respond to buffers.

If again, we go through a period of time, we may see some body condition loss or body weight loss and animals that have been exposed to repeated bouts of SARA, we may see secondary disease problems like epistaxis, which means bleeding from the nasal openings, this is from lung damage, pneumonia and of course lameness.

Although there has recently been much more of a concern about hind gut acidosis being more directly associated with the lameness issues rather than ruminal acidosis, so this is looking at the scenario.

This is a data from a study where they had continuous monitoring of the rumen pH.

And you can see the blue line up here represents what rumen pH we'd expect on a high forage diet, you can see above right around hovering around 6.6, 6.5, 6.6.

In contrast of feeding a high grain diet, we get this immediate drop in rumen and pH.

That's because of the rapid fermentation of sugars and starches.

You get a little bit of recovery as that animal is chewing more with eating the meal.

But then you get sort of, you know as they take additional meals and continued fermentation, we can see in this case this high grain meal.

We get continuous acid production probably from a, you know slower fermented starch diet.

And we have this prolonged and it takes a period of time here almost from 7:00 AM to to 3:00 PM you know, so we're looking at eight hours before they start to recover and get above this threshold.

And really what I said earlier, it's that time factor of being below this, 'cause this is all not allowing fiber fermentation to be taking place.

So I'm gonna answer, there's a question in the the Q&A that I think if I just get this information done, I'll go to that.

This was a study where they tried to or their goal was to induce SARA so they could start to investigate the disease process.

So they had a controlled diet, which was a total mixed ration.

It was made up of about 18% corn silage and 22% mixed haulage and a little bit of mixed hay.

And then they used high moisture corn quite a bit, 28% and then a protein supplement mix.

So a fair amount, you can see that forage concentrate ratio was 70:30 and they did feed a hundred grams of sodium bicarb.

And so this was a very small study, only four cows per treatment, they measured pH on a regular basis.

The SARA inducing or the intended SARA inducing diet made up 75% of that TMR and then they added 25% of a grain pellet and the grain pellet was basically half ground wheat and half ground barley.

Those are pretty significant as we're gonna talk about.

The type of starch or the source of starch is really important because the source as well as the processing of that starch really can impact the degradability in the rumen of the starch.

If we come over here to the right, we can see the rumen PH the on the control diet on average over the treatment period.

It kept a nice rumen pH of almost 6.4 and you can see the SARA induced did what just what they intended.

It dropped the pH to 5.7 and then they measured the time, the hours per day that it was either below six or 5.6.

And you can see on the control diet only 2.6 hours below six and 0.26 hours below 5.6.

So even on this controlled diet, because most likely the high moisture corn, we did see some drops, but look at that compared to the SARA diet we have over 15 and a half hours a day below six and almost 10 hours a day below 5.6.

So even though the pH is not highly significant in terms of an acidosis load, the time below the critical thresholds of functionality of the rumen are quite extensive.

And then what they did is they looked at a 48 hour invitro analysis using rumen fluid of corn silage.

And you can see the digestibility was higher for corn silage in the controlled diet versus the SARA diet.

And NDF degradability of the grass, hay was greatly reduced in the SARA diet.

So this is reinforcing what I said earlier about the decline in fiber digestibility and then you can see even with legume hay there was also a pretty significant drop.

And then you can see there was a decline in production or excuse me, in dry matter intake, but really no good decline in milk production, certainly the milk fat was lower than what we'd like to see, but statistically because of the small numbers of cows there was no differences here, but certainly altered composition of milk.

So the question here that kind of fits in with this, where cattle graze on grass and dry maze stalks, can this cause acidosis, generally not as we'll see the grass is very good relative to the maintaining rumen pH and ferment ability chewing, but buffering a lot's gonna depend on how much corn grain is still left.

But if it's dry maize stalks, my guess is that the corn is gonna be fairly crystalline in nature and not readily digested in the rumen, so I think you're probably gonna be okay on that.

Now one of the big concerns with acidosis, of course is right around the time of transition when the animals, when the cows are going from a late pregnancy diet, which is generally a high forage diet onto a high grain lactating type diet.

This is some data from one study that looked at a low starch diet, which was 21% starch on a dry matter basis in 37% neutral detergent fiber, and then a high starch diet, which was 27% starch and 32% NDF the cows were on the same dry diet.

And then this is days in milk and what we can see here is rumen pH on the lower starch diet was maintained much above that of the high starch diet.

So obviously the starch was having a negative effect.

And then we also see that the time below room pH of 5.8 was much more elevated in the variability, but much more elevated in the high starch animal.

So this is one of the challenges that we have in transitioning cows appropriately from the dry diet onto a lactating diet and there's been many adjustments.

I wanna show one more data set here.

This is some work out of Cornell where they fed two levels of starch.

The high starch diet contained somewhere between 26 and 28% starch, the low starch between 21 and 22.

And then a high fiber diet, which was an NDF of somewhere between 34 and 37 and a low fiber diet that was between 26 and 31.

And these animals were, or these cows were on a similar prepartum diet and then transitioned over onto these postpartum diets.

And what we can see is the high starch, high fiber diet outperformed in terms of intake.

If you remember that the previous data that I showed you, dry matter intake was significantly reduced in cows that had SARA and we see that here with the high starch low fiber diet.

And we see basically no difference between the low starch high fiber or the low starch, low fiber.

So there certainly seems to be an important interaction between fiber level and the starch level.

We know some of the work by Dr. Mike Allen when he was at Michigan State University talks about this very early postpartum cow is more sensitive to high grain diets in terms of negatively impacting the intake level because of the hepatic oxidation theory that he is put forward there.

They're more sensitive to their caloric status and they're not as compromised by fiber, not like what the high producing cow is.

So this really reinforces we may wanna seriously consider, you know an early fresh diet formulated in one way and then the peak milk diet to account for intakes and responses, so how do we prevent this then?

And basically this has been discussed in many papers, many of the review papers talking about SARA.

It's really a balancing act of the diet relative to rumen pH.

We have what we call the physically effective fiber.

Again, I'll define this process, which stimulates chewing, which then provides the buffer production versus the rumen fermentable carbohydrates which produce the acids that need to be buffered.

Now we wanna feed more fermentable carbohydrates for milk yield.

We know that as carbohydrates produce fermentable carbohydrates produce propionate, this generates much more glucose through gluconeogenesis and of course glucose goes to the memory gland and is made into lactose that drives milk yield.

However, this balancing point can be perturbed by environmental conditions, feeding management issues that can either promote or be a detriment to the diet itself as well as the dietary formulation.

So what are our goals then in formulating diets for carbohydrates?

The three basic goals are we wanna provide a low fill, highly fermentable diets to promote milk yield, but yet within that context, we wanna maintain an adequate rumen pH to maintain the normal dynamics that go on and we want a fairly consistent fermentation over time.

So I provide this graphic, I use this in terms of discussing how the rumen works.

The rumen bugs need a nitrogen source and I'm representing that with ammonia, 'cause that's what the cellulolytic bugs require exclusively.

And they have to have an energy source and the energy is coming from the fermentation of carbohydrates.

So these bugs cannot store the ammonia nor the energy.

And so they can only use both together to support their microbial growth and development and that's what this hatched area is representing what I call the utilized resources.

And so what's gonna happen in this case where we have a rapidly available nitrogen source, say, you know highly soluble fermented grass hay or alfalfa silage, grass silage or alfalfa silage, and that excess nitrogen's gonna get excreted.

And then this excess energy is just gonna get burned off through what has been termed energy burning type reactions.

We can also see the opposite.

We could see where the energy is readily available, so rapid to energy source, but we don't have the nitrogen until later on.

And so this is gonna be a scenario where in either of these cases we have all this energy being generated and essentially acid load that potentially can contribute to the subacute ruminal acidosis.

Ideally, this is what we wanna see.

We wanna see a nice fermentation, consistent fermentation.

Obviously there's gonna be little dips and bumps here relative to consumption of the diet and so on and for the most part we achieved this through the feeding of TMRs.

And so when we've moved away from the conventional feeding where you would go around the barn and you'd feed some grain or silage and then you come back and feed some hay and then you feed some more grain and so on, you know that led to a very unstable fermentation process and you know led to much more acidosis issues.

So the first thing we need to think about then is what is the source of carbohydrate and how does it ferment?

What is its degradability in the rumen?

So this is some older data that shows relative rate of fermentation over time when the first consumption of the diet.

And you can see that the soluble sugars go up very rapidly and then are pretty much gone.

And then you can see products like the Pectins, the Dexstrans, Fructans are very fermented, a little slower than the sugars, but more rapidly fermented.

And then your starches and glucans, and then finally your xylans and celluloses.

So this is your, you know your plant fiber sources here.

And then this is our starch and then this is our, you know fermentable oligosaccharides.

So ideally what we wanna do is we wanna try and feed a range of carbohydrates in the diet to allow for kind of this fermentation, continuous fermentation process.

And this is where many of our diets out West outperform our diets in the East, Midwest and East, because the western diets, when I was out in Oregon, we fed many different things like, you know vegetable waste and many other byproducts.

And so we took advantage of a lot of these Pectins, Dexstrans and then of course some starches, but we usually didn't have very heavy starch diets out there.

In contrast, in the Midwest of the US and the in the East, we rely heavily on corn silage and corn as our grain.

And so we basically accentuate this blue line and then depending on how that corn is processed, that may result in more rapid energy availability or slower energy availability.

But one or the other, you know we don't get this this nice, you know if you draw a kind of a ligned across here in terms of if you look at the fermentation, we would have something like this, you know total fermentation.

And so that's kind of what we want to try and achieve in the rumen.

All right, so here's another study that shows this.

This was a study done in sheep and they had a challenge that was put through rumen fistula on three separate days.

And they had a basal diet here that was made up of the, a grassland hay and then a wheat-based concentrate with 3% molasses and this was in a four to one ratio, so a fairly high forage diet.

And then the sheep were dosed with either wheat, corn or beet pulp.

And these were processed at 1.2% of their body weight through the rumen fistula.

And so what we see here, this is rumen and pH up here, total volatile fatty acids in the middle and then lactate down at the bottom graph.

And what we can see is ruminal pH the beet pulp, which is mostly Pectins and doesn't ferment to lactate, basically maintained a fairly high rumen normal pH.

The corn was slightly lower, but you can see the fairly substantial drop in pH in the wheat, we see this relative to the total volatile fatty acids.

So the ferment ability is lower on the wheat, because of the destruction of the organisms and then maintain a little bit higher on the beet pulp and in the corn.

And then when we look at the lactate production, you can see the dramatic increase in lactate.

so wheat is really well associated, because of its very rapid fermentation in the rumen to lactate to induce more of a clinical lactic acidosis.

Corn was more of a problem with inducing SARA and then beet pulp was a fairly normal, this is why we try to use more fermentable fiber sources in maintaining good rumen health and that's kind of where our whole formulation process is moving.

So what are some of the factors that affect ruminal starch digestibility?

Well, we just got done showing you that wheat is the worst.

Barley is close to that oats, starch ferments more rapidly than corn.

Corn generally is a much more crystalline nature of the starch.

Although there are sub differences in the genetics that we have in our corn that could change that somewhat, the dry matter of the grain.

So moisture as we insile these grains, the moisture increases the ferment ability, insiling and insiling time will increase the starch degradability.

So with corn silage, the longer it's in the silo, the more available that starch becomes the fineness of the grind or the flake density.

So we have corn that has more of a flowery endosperm, which is more readily available in a vitreous endosperm.

And there are certain genetic strains that have higher amounts, more flowery type corn versus more vitreous type corn and that's going to impact the availability.

Fermentable starch intake overall, the starch can suppress digestibility rumen consistency or passage.

And then dry matter intake, the passage rate also will influence the degradability.

This is some data from Cumberland Valley Analytical services, one of the premier labs here in the US and you're looking at the percent digested of corn grain.

The corn starch digested over time based on different grind sizes, so we can have very fine corn or very coarse corn.

So the coarse corn is way down here in this fine corn.

You could see how the boost and very quick fermentation, and this is why in labs we generally look at rate of fermentation at seven hours and end rate at fermentation at 24 hours to assess starch to great ability in the rumen and what impact it may have.

So that's the carbohydrate side.

Now, as I said, it's an interaction between the starch and the fiber components in the diet.

And so we with, you know when Dr. Peter Van Seuss at Cornell developed the Van Seuss detergent system, we finally got rid of, at least from a practical standpoint, the crude fiber analysis, which was very inadequate in characterizing the true plant cell wall.

And we use NDF as the measure of plant cell wall and the impact that it has on feed intake.

You know, this is where Dave Merton's, when he was at Cornell, you know, looked at NDF capacity, because the cow cannot digest the NDF, it's the microbes that digest the NDF.

And so, and that takes time.

The are slow growing bugs compared to the starch fermenting bugs.

And as a consequence, you know that NDF sits there for a long period of time.

Now, but we've have come to understand it's just not the NDF by itself, we know that there are other issues and so initially what we looked at is defining what we called effective NDF.

And so effective NDF or ENDF was used relative to measuring the response of milk fat percent.

So in other words, we looked at not just the NDF, but characterize what we call the effective NDF based on whether or not there was a milk response, a milk fat response, 'cause we know that the more digestible the NDF, we can get more acetate, more butyrate that can contribute to substrate for the memory gland to make milk fat.

But we also know that other non NDF components of the diet, such as intrinsic buffering in the animal, the fat in the diet, soluble protein in the diet that can promote fiber digestion and the soluble carbohydrate, which would be the soluble fiber also can contribute.

So it was really difficult to precisely define an NDF requirement.

Then Dr. Merton's developed the physically effective NDF and this is based on chewing activity.

So this is gonna be more directly associated with that buffering capacity and physically effective NDF was a function of particle size and the chemical nature of NDF, the lignin bonding and so the degradability.

In the most recent dairy NRC or now called the NASEM, they introduced a new variation on this called physically adjusted NDF and physically adjusted NDF is our new approach.

And I'll show some of this information taking into account particle size based on distribution on the particle separator and the chemical nature of the NDF.

So ration formulation for dietary fiber, we wanna balance rations to meet the total NDF, the physically effective NDF, which approximately 21% of dry matter requirement.

We can start by looking at forage fiber intake at about approximately 1% of body weight or 75% of the neutral detergent fiber, this was some of our original approaches here.

And if we had a poor quality fiber based on digestibility, we could lab determined digestibility, we could substitute more fast fiber sources like the beet pulp and wheat mids, soy holes, things like that, citrus pulp.

If there's a lack of physically effective NDF, then we can use small amounts of grass hay, mature grass hay, whole cotton seed or chopped straw in the diet.

So this was sort of our typical approach, you know based on the current information and if we had good quality fiber, we could formulate towards a maximum fiscally effective NDF and NDF capacity.

But then again, we wanted to monitor dry matter intake and animal performance to make sure we weren't pushing it too far.

So how do we measure this physically effective factor or physically effective neutral detergent fiber.

And Dave Mertens had done his work using a vertical sieving system and using the material in a dry state and that wasn't very practical for using on the farms.

One of my colleagues here at Penn State, Dr. Judd Hendricks, him and his graduate students developed what became to be known as the Penn State Particle Separator and this was used maybe inappropriately in the early stages.

It didn't conform to the merton's information, but that's where they developed the different screens.

This lower sieve, there was an initial lower sieve that was 1.18 because that was the, this is millimeters of the pore size, that's what Merton's had used, but it just didn't fit.

But when we developed the new pore size of four millimeters, then when you added up the material on these top three screens, it came up, you can use it as a percent and then you multiply that value times the NDF content and that's the physically effective NDF.

So this percentage of material on these top three screens became the PEF factor, you know the physically effective factor.

And so that's really started to improve our ability to formulate diets better for the fiber component and not compromise intake.

Now as I mentioned in the new NRC publication or the NASEM publication in 2021, they introduced based on a collaborative work published in the Journal of Dairy Science in 2017 by White and colleagues physically adjusted NDF or what's now termed paNDF.

And so this is our newest method of assessing the role of fiber in the ruminant diet.

And what's important about this one, physical effective NDF only contributes to potential chewing activity and saliva production.

In this method there's an interaction, they looked at the interaction with starch content in the diet particle size and what they called fiber fragility and this would be the fragmentation of the plant fiber in the rumen.

And this was based on a NDF, excuse me, ADF to NDF ratio for the forage.

So the purpose of this approach was to estimate the dietary fiber adequacy and maintain good ruminal conditions, alright, to maintain good fiber digestion.

And so the data that I'm gonna show you from this is based on maintaining a rumen pH of six or 6.1.

And what this system uses is they use the percent of material retained on the top two screens of the Penn State particle separator.

So the very top screen, which is 19 millimeters, 19.1 millimeters, and then the second screen, which is 7.9 or eight millimeter sieves.

And then they modeled available data to look at many different dietary parameters that could influence this.

And essentially they, with the fragility, they're able to address both physical and chemical factors.

And in contrast to physically effective NDF, this assumes the NDF is uniformly distributed overall, all particles irrespective of size and that's not the case and that's where physically adjusted NDF sort of picks up and moves forward.

So this is the graphics from this publication looking at the effects of starch.

I know this is very, you know, overwhelming, but if you look on the left hand side here, obviously there's many, many graphics here, so let me just orient this.

So here is the dry matter material on the eight millimeter screen, so the second screen, so it ranges from 20 to 80%, okay?

And then the dry matter material on the 19 millimeter screen.

And we have six, 12 and 18, these are above what we generally recommend.

And then we have the starch content of the diet.

So this row here is at 15% starch, 17 and a 20, 22 and a half, 25, 27, 30 and 32.5.

So across a row you have the same starch level.

And then what we're looking at is plots of the eight millimeter screen versus having a low amount, a moderate amount, and a higher amount on the upper screen.

And then finally we have forage NDF as a percent of dry matter and this ranges from 10 to 30%.

And so what I want you to show or want to show you with this data, so if we just look at this column of six, I put this red line in where it about 15% neutral detergent fiber, forage fiber as a percent of the dry matter.

We have a fairly straight, but what I'm looking at is the, if we move up to 22 or so and beyond, we start to see this decline in need to have material on this second screen.

And this is just because of the higher forage NDF that's there within the starch.

And we can see the same kind of, you know drop in the amount on that eight millimeter screen.

And you can see as we have more material on the top, this asymptote or deflection occurs slightly earlier than what we see with the other material on this.

And this is all based on trying to maintain for these circumstances, this amount of starch, this amount of material on the top screen and the forage, how much material we need to have on the eight millimeter screen.

So this gives us some diagnostic capabilities to start to look at this.

We also can look at forge fragility, so this is set up in a very similar way.

We have dry matter material on the eight millimeter screen.

We have the material on the top screen up here and then forage, diet forage NDF as a percentage dry matter.

And now we look at ADF to NDF ratio as a measure of fragility.

Point three eight is gonna be mostly grasses, this is gonna be sort of a mix of grass and then this is gonna be mostly our legumes.

And basically we know that legumes have a, are much more fragile than grasses.

And essentially what we're seeing now is the drop and the amount that's needed on this second screen increases with the increasing fragility.

So if you can see up here that the amount on the second screen is only in between the 25 and 50 here it's between 50 and 75 and then at 75 and above for minimal material on the top screen.

But we see this much greater need when we have more fragile forages because it's not gonna stimulate the rumination, it's not gonna stimulate the buffer production and thereby not help with the acidosis load.

Alright, so this whole process is available in an app that can go on your cell phone, it's called MUNCH.

You go to, you know Google store or the iPad store or whatever it is, and you can download this free of charge.

This is based on again the NASEM publication.

And you can see here the inputs dietary characteristics.

They need to be on a dry matter basis.

So forage, NDF, total forage, wet forage, cotton seed, whether it's hulls, whole hulls or meal.

And then we need to know the NDF, ADF crude protein and starch content, the body weight of the animal, this is gonna dictate rate of passage.

And then the Penn state particle separator, we need to know how much is on the 19 millimeter sieve and the 1.8 is an optional.

And then what the output is, once you put this information is it tells you how much material should be on that eight millimeter sieve and it will give you the minutes per day of rumination.

So if you're monitoring rumination and have all of this information, this gives you a much greater ability to manage rumen health in the animals.

Alright, real quick, some of the non nutritional factors that can cause this drop in pH in the rumen, of course sorting of the feed by the cow not pushing feed up, you know so feed bunk management over mixing the TMR two small particle size, inadequate bunk space causing animals to slug feed and empty bunks from much more than three to three to five hours per day.

Now I know some people feed to an empty bunk, but that takes some finessing of feed bunk management.

We can also see the issues with particle size variation in the TMR due to overfilling the mixer wagon or under mixing under processing of hay, dull blades or worn kicker plates in the mixer wagon, improper loading of liquids, improper ingredient loading sequence for the mixer wagon.

And then low inclusion products such as your grain or your mineral mixes and things like that may not be mixed thoroughly, they need to be mixed.

And so again, we can use the Penn state particle separator to start to look at how well we've done and how consistent we are.

The last thing I wanted to touch on is heat stress.

This has a tremendous impact on feed intake and digestibility.

Heat stress can increase rumen retention time, so we get greater ferment ability, reduces rumen contractions.

We can see reduced rumen buffering due to saliva loss and some decreased rumination, we can see increased feed sorting, more feed refusals and reduced dry matter intake.

What was really interesting, and this is some work from the University of Florida back in 1970, they looked at intakes of diets under cool and hot conditions.

So cool conditions were 18.3 degrees Celsius, hot conditions were 29.4% or degrees Celsius.

And then they had a high grain or high grain and a high roughage diet.

So you can see between cool and hot irrespective there was a drop in rumen pH and then between high roughage and a high grain there was a drop.

And then when you looked at cool high roughage versus hot high roughage, there was still a drop.

And under the high grain diet, a much more decline.

So it seems under heat stress, even with the same diets we can see more ruminal acidosis potentially occurring, how do we prevent acidosis with all of this?

Well, obviously we're gonna focus a lot on diet formulation.

The fiber content, the percent forage the physically effective NDF or the newer system of the physically adjusted NDF.

And then we also have to consider the starch and I'll even include the sugar starch content and its degradability.

Then method of feeding, we'd like to use a TMR if we are feeding a conventional type where we're feeding grain, we want to feed more often the grain more often in smaller amounts.

Whether or not we really need a gradual adjustment or adaptation to high starches, high starch diets is still in question.

I think if the fiber's there, we can do it.

There's dietary buffers we can add to the diet bicarb, magnesium oxide and then rumen modifiers, ionophores resin is approved in many countries to help with this.

Yeast is also been shown to help stabilize rumen fermentation.

So I wanna just finish up here by progressing through the recommendations.

This was from the NRC 2001.

They talked about the minimum forage NDF in the diet, the minimum total NDF that would be in the diet, and then the maximum starch that would be in the diet.

So they didn't really think about the interactions and some of the things that the physically effective NDF would, but these are generally decent guidelines to at least get started, Mike Allen sort of added some qualifiers to this.

The forage NDF as a percent of dry matter, he said between 17 and 28, that's kind of high there, but you know if you had higher dry matter intake, you can, you wanna move towards more forage, faster ruminal clearance, you wanna have higher forage intake.

Finally chopped forages, higher forage intake, high diet starch, low non fiber forage sources or forage concentrates.

You wanna push higher starch gradability push greater forage content.

If you're adding extra buffers, you can go to the lower side grain fed separately and infrequently.

You certainly wanna run a higher forage NDF limited bunk space.

You can see, you know all those things, those potential things that could increase the acid load, we wanna push towards higher fiber to compensate.

This is, oops, recommendations that were again, suggested without kind of these interactions, but more from a practical experiential.

There's recommendations on the starch content for closeup early peak and mid and late lactation.

I'm not sure I would go as high as 27% in the early anymore.

The amount of fermentable starch, certainly we want lower fermentable starch and then this would be the actual fermentable starch in the diet, so we would have to measure some ferment ability.

So these were things recommendations based on looking at just the starch side of the equation and then specifically early lactation cows, this is the group that's at greatest risk.

And so some recommendations on total NDF or fermentable NDF, the sugar content, the starch content, the fermentable starch, the soluble fiber, fermentable soluble fiber and the non carbohydrate content.

So this was some of the early development of recommendations on the carbohydrate side.

This is a table from the NASEM publication 2021 where you're looking at the TMR composition.

Now you can see that the amount of forage, the starch content, the NDF and the fermentable NDF and then maintenance of a 6.0 pH.

The amount of material that's on the 19 millimeter sieve, so you have three and then nine and 15.

And then this would be what the minimum percent that needs to be on the eight millimeter sieve for these different diets.

And then if you wanna maintain a better Reuben pH, they have higher amounts here on the screen, so this is really finessing the whole process.

And I'll finish up with this graphic.

This is from a review paper in 2004 by Bill Stone talking about nutritional management to prevent acidosis and again we have recommendations on the NDF.

Here's the risk of SARA is increased with lower NDF in the diet, lower forage NDF, lower physically effective NDF and obviously the rumen pH and then higher non-fire carbohydrates and non-structural carbohydrates.

So the non-fire carbohydrates is gonna include fermentable fiber and the non-structural is your sugars and starches and then he goes on to explain in the lower part of this figure some forage considerations.

So this would be, you know the adaptations.

If you're at higher risk of SARA with your diet, then your forage particle size should be longer.

Your rate of fiber digestion, it should be slower.

All right, so you have more the chewing activity, your concentrate consideration, starch digestibility should be slower.

The use of high fiber byproduct should be increased and the use of buffers should be increased.

And in management, environmental considerations, heat stress, stall bunk overcrowding should be minimalized in a situation of high risk, stall comfort should be excellent.

Feeding systems should be ATMLR foraged dry matter should be consistently accurate and silage obtained for a load of feed should be the entire height or the face.

So in other words, we have to really be careful in doing all the right things.

If we have a diet that has a high risk of SARA, so I'll finish with this, we know cows respond to consistency, they want the same thing day in and day out.

So consistent, high quality forages, a consistent feeding program relative to feed availability and the timing of feeding.

We want lower variability in the bunker.

We wanna minimize sorting.

We want to have correct dry matters for our high moisture feeds.

And consistency in ration preparation, consistency in water quality and availability.

We know that then with these kind of things, our feeding management should focus on eliminating those sources of variation just like what was shown in that previous figure, the things that we need to tighten up on.

And so that's ultimately, it's not just diet, we can't separate the environment, your feeding management practices and the diet into individual entities to say okay, this is how much fiber you need to feed, absolutely or how much starch you need to feed.

And again, we also have the cow that could be variable depending on some of her genetics.

So with that Michael, I hope I've covered some of the questions that we may have and I'll address this, here's a question here.

We use fine ground corn in our partial mixed ration, PMR and I think we have a substantial amount of wheat mids in our robot pellet to help with pellet integrity.

Are wheat mids a good option or is there something that might be better?

No, soy hulls or wheat mids would be great there, Carl, with that fine ground corn, you're gonna have greater ferment ability, that's gonna be a challenge.

But the wheat mids, this is a very nice fermentable fiber source with a little bit of protein in there.

That's nice and that should really work.

I'm really happy using that in robot mixes to try and have that pellet there.

- I would like to have a more comment on the question.

I noticed one thing and perhaps our audience did notice that too, nutrition is important part of keeping production up keeping animal healthy.

But what I noticed during class four or five webinars, whether it was with you or Dr (indistinct) from Minnesota, that management plays quite an important role and that's something that producers can do on their own on daily basis without having any special advice or anything like that.

You know, and I remember we were talking about that one time that researchers in Wisconsin, they were doing survey on their cows regarding subclinical ketosis and they find out that nutrition was a maybe 15 to 20% problem, the rest was actually due to farm management.

- So yeah, I agree and as much as, you know being a nutritionist, I wanna focus on nutrition and nutrition is certainly important, but how that nutrition is provided is such a critical issue and unfortunately many systems people have their management and you know as being humans we don't wanna blame ourselves and so we usually are not willing to address the faults that we may or should recognize.

And so I think it's important for consultants to help guide some of those management decisions.

Some of these things that I talked about in terms of, you know, going out and measuring stalls and looking at the distribution and the consistency of distribution of particle size and the mixer wagon and things like that.

- Alright, since we don't have any more questions, so I would like to thank you for the information.

Oh, we have one here.

Additional popup.

Well that's a large amount of chemistry to digest.

We certainly need to repeat this webinar and look up more information along the way, I'm certainly very interested.

I'm looking at this from a feeding, very good.

- Yeah, that's dairy goats would be another challenge.

We have many of the same circumstances where we feed dairy goats in the milking parlor and they get two very large grain meals.

And so we see a lot of ruminal acidosis and SARA in dairy goats.

Many of the big goat farms that I work with have moved to a TMR feeding system and obviously is not practical in many of our smaller dairy goats.

But the concepts that we've talked about today, spreading your concentrate feeds out, you know addressing the fiber.

But the challenge we have is goats are not cows, goats are not small cows.

They have a faster rate of passage, they have greater chewing ability, so there are some unique aspects that need to be addressed there.

- Okay, unless somebody is typing another question and indeed that haven't, how can access the previous webinar?

I will send you links to all these previous webinars.

This webinar will be probably edited for posting probably in three, four days.

So afterwards I'll be sending all links to all participants.

Can this be added in the future about the goats?

I suppose you mean like a program on the acidosis or nutrition in goats?

I think it can, I don't see any reason.

- Yeah, I've been doing a number of webinars for, matter of fact I just did one for the Ontario Dairy Goat associate or co-op on milking just last Thursday.

So we have the capabilities of doing it through our webinars or through different associations.

I've talked to the Texas Mini Milkers and a number of other sheep and goat groups on this kind of information.

- Alright, well that would conclude our today's session and the last session and thank you Dr. Vanson for your time and for the information.

- All right.

Thank you Michael, for the opportunity to share this information and again, I hope it's of use to the many listeners we have.

- Thank you. - All right, thank you.