Please note the recording was before the new NASEM model was released. However, there is still a lot of good information from Dr. Weiss beyond those recommendations. This Real Science Exchange podcast episode was recorded during a webinar from Balchem’s Real Science Lecture Series. You can find it at balchem.com/realscience.
Please note the recording was before the new NASEM model was released. However, there is still a lot of good information from Dr. Weiss beyond those recommendations. This Real Science Exchange podcast episode was recorded during a webinar from Balchem’s Real Science Lecture Series. You can find it at balchem.com/realscience.
Most ration formulation software uses the 2001 NRC mineral equations. The basic concept of the 2001 NRC mineral requirements is to feed enough absorbable minerals to maintain adequate labile body stores and fluid concentrations. Minerals are lost each day via excretion in feces and urine, milk production, and incorporation into tissues or the fetus in the case of growing or pregnant animals. We have decent data to predict mineral concentrations of milk, growth, and the fetus; however, the endogenous loss in feces is much harder to capture. Absorption coefficients (AC) for most minerals are exceedingly difficult to measure. (0:29)
The NRC requirements are the means of several experiments. Feeding to the mean results in half the cows being fed adequately or in excess, and half are not fed enough. In human nutrition, recommended daily allowances for vitamins and minerals are calculated as the mean plus two standard deviations, which statistically meets the requirement for 97% of the population. Since the standard deviation of the requirement is hard to acquire, human nutrition uses the same standard deviation for energy metabolism, around 20%. Dr. Weiss feels this is a reasonable safety factor for minerals for animals as well. He recommends feeding about 1.2 times the NRC requirement while keeping an eye on the maximum tolerable limit for the mineral in question. (4:59)
How do we measure absorption? We measure the minerals in the diet, we apply AC, and we get grams or milligrams of absorbed minerals available for the animal to use. Dr. Weiss details some of the complex methodology involved in trying to obtain AC. Feces contain not only unabsorbed dietary minerals but also endogenous/metabolic minerals (e.g., intestinal cells, enzymes, etc.) and homeostatic excretion of minerals (e.g., dumping excess minerals). In the 2001 NRC, the endogenous fecal for almost every mineral is a function of body weight, which is incorrect. It should be a function of dry matter intake. (8:40)
Endogenous fecal losses can also be measured using stable or radioactive isotopes. This method is extremely expensive and if radioactive isotopes are used, management of radioactive waste becomes an issue. Thus, most of the AC for trace minerals that used these methods are 50-60 years old. (15:33)
Dr. Weiss details some of the issues with calcium requirements in the 2001 NRC leading to overestimation of calcium absorption for many calcium sources and overestimation of the maintenance requirement due to endogenous fecal being calculated using body weight. Organic and inorganic phosphorus have different AC, so partitioning between organic and inorganic will give a more accurate estimate of the requirement. (16:33)
Potassium has a linear antagonistic effect on magnesium. You can feed more magnesium to overcome this antagonism, but you won’t ever eliminate it. If you feed a few percent added fat as long-chain fatty acids, Dr. Weiss recommends feeding 10-20% more magnesium to account for soap formation in the rumen. (19:17)
It’s much more difficult to measure AC for trace minerals due to multiple antagonists, interactions among different minerals, and regulated absorption. In addition, AC for trace minerals is very low, which means a small change in the AC can have a huge impact on diet formulation. All feeds in the NRC system have the same AC for each trace mineral and we know that’s not right. (25:39)
Dr. Weiss gives an overview of different trace mineral antagonisms and interactions and details his approach to formulation if he has absorption data for a particular ingredient. He also gives his estimates of revised AC for several minerals. (28:07)
In summary, the factorial NRC approach only fits 50% of the population. Feeding an extra 10-20% above the NRC requirement includes about 97% of the population. We need to continue to account for more sources of variation in AC. Interactions need to be top of mind when considering mineral requirements and diet formulation. (37:39)
Dr. Weiss takes a series of questions from the webinar audience. (40:50)
Please subscribe and share with your industry friends to invite more people to join us at the Real Science Exchange virtual pub table.
If you want one of our Real Science Exchange t-shirts, screenshot your rating, review, or subscription, and email a picture to anh.marketing@balchem.com. Include your size and mailing address, and we’ll mail you a shirt.
Moderator (00:00:00):
The following podcast is taken from a webinar titled, “Assessing Mineral Bioavailability in Real World Implications”, presented by Dr. Bill Weiss from The Ohio State University. To view the full webinar and access the slides referenced during this podcast, visit balchem.com/realscience and use the search bar to jump to this webinar from March 2nd, 2021.
Dr. Bill Weiss (00:00:26):
Good morning. From a very sunny, bright Worcester, Ohio. Today's webinar is on minerals, and obviously minerals is a broad topics. I had to be quite selective on what I'm gonna talk about. So I'm, I'm not gonna address every mineral, but I wanna talk about some principles and, and some application, but I will not get into every single mineral. Okay. No matter which software you use to formulate the mineral component is almost sure for certain NRC based, these different models may have different amino acid models, different energy models, but the mineral equations are pretty much right out of NRC. And the basic concept from 2001 NRC was the requirement for a mineral for a given mineral was basically what to meet this in the blue box here. And that was to feed enough absorbable minerals to maintain body stores, body fluid concentrations, and allow the cow to do what we want it to do.
Dr. Bill Weiss (00:01:34):
So to do that, we lose every day. A cow is gonna excrete a certain amount of absorbed mineral via feces a little bit via urine. That's a pretty small loss for most minerals, but this is mineral that was absorbed and now is being sloughed or lost in secretions. And so the cow has to replace that. Or, or body stores drop minerals are in milk, so we have to replace the minerals lost in milk every day. If the animal is growing then this isn't really lost, but it, this mineral has to be deposited into new tissue to maintain body stores. And then lastly, if the cow is pregnant she's accreting mineral in the fetus and fluids, those have to be replaced. So we have to meet all these needs along with without losing body stores, otherwise, we're not meeting the requirement.
Dr. Bill Weiss (00:02:31):
When we break this down, these three here, milk growth and fetus we have decent data on the concentrations on that. It's not especially the, the fetus is kind of old data, but it's reasonable data. So the, the requirements for these, I think, are pretty good maintenance though, which is feces. Inevitable loss in feces in urine is very difficult to measure. And that's, that's I'm gonna talk a bit about that as well. So this is, this requirement here is probably the least well known or the one we have the least amount of confidence in. And for some minerals, it's the biggest, biggest single requirement. So we have some issues here on requirements. We also have to maintain adequate stores. I can have a deficient animal feed enough minerals to do all these things, but she's still deficient. So we have to know when an animal is adequate. We have to feed enough mineral to get up to adequate status and then maintain that for some minerals. We know what is adequate. We have markers for adequacy. Other ones we, we really don't. And then the last part of this is absorbed. And that's what most of this talk is gonna be about, is this is not an easy thing to measure. Absorb me absorption coefficients for most minerals are exceedingly difficult to get.
Commercial (00:04:03):
Welcome to the next generation in chelated minerals. Introducing new KeyShure Plus amino acid chelated minerals from Balchem. KeyShure Plus delivers a higher concentration of mineral with a superior amino acid profile. The higher mineral content adds formulation flexibility opening up space in the ration, and also reduces the carbon footprint. The superior amino acid profile delivers 28% protein from microbial biomass and reduces the amount of supplemental lysine needed in the ration. The KeyShure Plus line also offers a granulated form for improved handling characteristics and reduced dust. Visit balchem.com to see how the new KeyShure Plus can deliver the added benefits you need to improve performance and reduce manufacturing hurdles.
Dr. Bill Weiss (00:04:54):
Okay, another issue with factorial, and I should mention, if you have the handout, I hit a few slides, so just move ahead. I I didn't change the order, but in theory, if we, the requirement we we produce is the mean that we take bunch of different experiments come up with equations from these different experiments, and we're, we're generating requirement for the mean animal of a, a certain animal of certain body weight, certain milk. And with the mean, that means half the cows are fed adequately or excess, half the cows are not fed enough. If we feed strictly to the mean, NRC is the mean. That's, that's their job is to do the mean.
Dr. Bill Weiss (00:05:41):
If you look at the human system or the, the US system for humans, you see a, they have a, they don't call it a requirement, they call it a an RDAA recommended daily allowance. And what the RDA is, it's the, the average requirement plus two standard deviations. And so the RDA for the human system, its goal is to feed essentially a hundred percent of the population, and statistically it's a little more than 97%. So for animal nutrition, we ought do something similar. If we don't wanna feed just the mean, we wanna feed a bigger proportion of the population. The big problem with this, this approach though, is you need a standard deviation on the requirement. And, and for humans, they, for most minerals, they have no idea what the variance is. And so what they do is they use the same standard deviation they get for energy metabolism, and that's the CV for energy metabolism for a specific human population is about 20%.
Dr. Bill Weiss (00:06:48):
And so the RDA for most minerals and vitamins is the mean times 1.2 20% extra. And I, I think that's a very reasonable safety factor for minerals for animals as well. 10 to 20% above what? NRC? And it's not. It, it's not, I don't consider that overfeeding. It's overfeeding an individual, but it's not overfeeding the population. It's feeding most of the population correctly, but it's only 10 or 20%. It's not a hundred percent, which I see too often. So feed excess of about 1.2 times NRC. The other thing I always wanna remind people of is, is there everyone, most nutritionists are more than willing to feed more than requirement. And as I just said, they should. But people forget on the other end of these things, everything is toxic in excess. And for minerals, we start seeing negative signs. Or at the point we start seeing negative things.
Dr. Bill Weiss (00:07:48):
We call that the maximum tolerable level. It could be as little as reduced intake and reduced milk, or it could be something major like a, a very serious i illness or disease. This also has uncertainty. So if you're gonna add 20% to this, maybe you ought to subtract 20% from the MTL. So, for example, copper has a an MTL of about 40 parts per million. You know, you want most animals to be safe, so maybe you ought to reduce that by and, and say, I don't want to feed anything more than 30 or 35 parts per million copper. So just be aware the MTL is also a mean. And so stay, stay away from it. Don't go right up to the edge. Alright what we're gonna talk about mostly is absorption. So the, the basic system is we measure the mineral in the diet, we apply absorption coefficients, and we get grams or milligrams of, of absorbed mineral that are available for use of the animal. We, for most, for most minerals, commercial labs can measure, measure, feed stuff quite accurately. There's a iodine is more difficult to measure. Selenium is more difficult to measure. But most minerals, we have good lab assays, but we have constants. These are almost the absorption coefficients are almost all constants, which we know isn't the way it is. But that's, that's the data we have.
Dr. Bill Weiss (00:09:19):
So how do we get these things? I wanna spend just a little bit of time on, on the methodology. So you appreciate just how difficult it is to get these numbers. One is we could do just mass balance, and that means we, we measure how much is eaten, how much mineral is eaten. We can measure how much is in fecal to get apparent absorption shown down here, just intake minus fecal, we can get apparent balance by also subtracting out milk and also subtracting out urine. This, this apparent absorption is not the availability coefficient. Too many people think that's all, all you have to do, and, and you, you can't do it just collecting fecal samples or fe fecal output and subtracting intake does not yield absorption coefficient.
Dr. Bill Weiss (00:10:11):
And the problem is, is the, in the feces, there is unabsorbed dietary mineral. That's the number we really want. How much of the mineral that you fed was truly not absorbed by the cow. But in fe fecal samples, we also have this stuff called endogenous fecal mineral. This can be sloughed intestinal cells, it can be some fluid secretions it could be some enzymes, but it's, it's stuff that it's minerals that were absorbed once and now are being excreted. You have another fraction, what I call as homeostatic excretion, some minerals for cows to maintain. When you feed excess minerals for them to maintain the proper amounts in their body, they dump excess, they absorb it, but then they dump excess out in feces. Some minerals are excreted, excess in urine, some in feces, manganese, some of the trace minerals go out in feces.
Dr. Bill Weiss (00:11:14):
So what we really to get the true availability, which is the absorption coefficient, it's intake minus feces, but then, or fecal mineral. But then we also have to get rid of metabolic fecal mineral and this homeostatic fecal mineral. These are not easy to measure. They're extremely difficult to measure. The other thing here is we wanna measure true availability. When cows are fed at about the requirement, some minerals, the, the, the absorption is, is regulated. And so I feed a lot of extra minerals. The absorption coefficient would be, would be low because the, the cow downregulates absorption sites. And it's simply not absorbed that it's available to the cow, but the cow just doesn't need it and won't absorb it. So we have to have the, we have to measure these at what we think is about the requirement to get accurate measures of availability coefficients.
Dr. Bill Weiss (00:12:17):
Now for some minerals, we can actually use fecal excretion almost exclusively. And this is an example with potassium. This is called a Lucas plot. It's been around for a very long time. It's used for a lot of nutrients. And what we do is we plot the intake or concentration, but the intake of, of, in this example, it's potassium versus the intake of absorbed fos absorbed calcium, absorbed potassium. I'll get it right here. So it's what they ate versus what they ate, minus what goes out in feces. No adjustments, just total fecal loss. And we plot these two, and it if for some minerals, we get a nice straight line, good fit. And for this plot to work the intercept, oops, sorry, the intercept has to be negative or zero, but it, it cannot be positive. And the slope has to be equal to or less than one, statistically equal to or less than one.
Dr. Bill Weiss (00:13:21):
The slope is the absorption coefficient. And what this is saying is potassium is absorbed with a hundred percent efficiency. The absorption coefficiency is 100% because this is not statistically different from one. The intercept is the endogenous fecal loss. So this is saying these cows lose 2.5 grams of pot of potassium for every kilogram of intake. So this would be the fecal maintenance requirement. This is the absorption coefficient, and it works well for electrolytes. This method works well for electrolytes. A point I wanna make here is with this, with the old NRC endogenous fecal for almost every mineral was a function of body weight, weight. And that's incorrect. That it should not be a function of body weight. It should be a function of dry matter intake. And you're gonna say, well, does that really matter? And I, it matters a lot. You can have a dry count of lactating count that weigh the same with the old system.
Dr. Bill Weiss (00:14:27):
They'd all have the same maintenance requirement for minerals. That's not correct. A lactating cow is going to eat two or three times more than a dry cow. Her endogenous fecal loss should be two or three times what a dry cow is. So one thing we we need to do is switch on our requirement end is switch endogenous fecal or maintenance to make it a function of intake. And that should help us quite a bit on, on comparing dry cows and lactating cows. Okay. This approach here, as I mentioned, works for the str strong ions. You can read this yourself, but potassium, sodium, and chloride. This is the method we should use to get absorption coefficients and metabolic fecal requirement. We can also use it with magnesium, but there's some adjustments for magnesium. It's because of different sources and antagonists, but we can use it for magnesium.
Dr. Bill Weiss (00:15:28):
Another a, a way to measure endogenous fecal losses is that the standard way is using isotopes. We feed stable or radioactive is soaps of the minerals. And then we measure excretion in the feces. The isotopes come from the endogenous and the non, non labeled as diet. It works very good. This is how human we, we determine it. For humans, it's very expensive. And for cows it's very, very expensive. 'cause They're so big. If we use radioactive iso, which is almost impossible to use now we have the waste problem. And because of this difficulty, most of the, for especially the trace minerals, most of the absorption coefficients are 50, 60 years old. They were determined back when they could feed radioactive manganese and radioactive calcium. We can't do that now. So just be aware of these absorption coefficients we use are are quite old.
Dr. Bill Weiss (00:16:27):
Some of 'em are quite old, okay, on macros the acs I think are getting quite good. On average, we've gotten more data. We've got better ways to analyze the old data. A couple issues here from NRC 2001, they gave a calcium chloride an absorption coefficient of 95% that was based on calf data. Calves are better absorbers of minerals and ruminants functioning ruminants. If you look at the, the data for older cattle, it's only about 60%. And you're gonna say, well, that's just one feed. What's the big deal? Well, the problem is, and for a lot of these minerals, we will have an absorption co fisher for one or two sources. And we, everything is relative to that one or two source. And calcium chloride was one of those reference sources. So that means a lot of minerals, a lot of sources of calcium were overestimated. The absorption was overestimated for almost all, all all calcium sources.
Dr. Bill Weiss (00:17:36):
Also, when we start using endo, ef, I'm just is endogenous fecal. But when we start applying endogenous fecal as a function of intake rather than body weight, we get more accurate estimates. And the nr, the old NRC requirement too high. So some of this error will cancel out. We overestimated absorption, we overestimated maintenance requirement. So even if we correct for absorption coefficient, it's not gonna have a huge effect on the average diet. It's gonna have effects on certain diets, but not on the average diet phosphorus. The ONRC gave feeds not, not supplements, but feeds absorption coefficients of I think 64 and 70%. 70% for concentrates, 60 or 64. For, for forages, there's been a lot of work on phosphorus. And, and one thing we can do is partition phosphorus into inorganic In organic, these have different absorption coefficients. So we could, you could send a feed in, it gets a assay for organic and inorganic, and we can just apply, apply math here.
Dr. Bill Weiss (00:18:50):
See grass hay with two thirds or inorganic. One third organic would have an absorption coefficient of 79 bean meal would have an absorption coefficient of 69. So with, with this system, we're now starting to make absorption coefficients, not constants. We're, we're putting variation into them. Like we know they're, they have magnesium. It's a, it's a tricky one because there's so many antagonists. Most, for most macro minerals antagonists aren't an issue except for magnesium. There's a linear effect or linear, linear antagonist of potassium. You feed more K cows absorb less magnesium, linear function, long chain fatty acids. This isn't, we don't know how this relates whether it's a, a linear or whatever, but if you're feeding a few percent added fat I would feed 10 to 20% more magnesium to account for what's for soap formation in the rumen. The endogenous fecal now is a percent, or as, as a unit of intake is about 0.3 milligrams per kilogram.
Dr. Bill Weiss (00:20:00):
DMI. And this is a good number. So we can use this to, to come up with a ACS by using apparent absorption. These are two studies here. One we did a long time ago, and this one's outta Europe. It just shows the linear relationship or the linear antagonism of dietary potassium versus magnesium absorption. But you'll notice though, is in, in our study, and this is actually a meta-analysis, we got a negative coefficient of 7.5 units of absorption for every 1% increase in k. The study here outta Europe only got a 3.1 unit decrease. And you're gonna say, well, my god, what's, why, why are these so different? This was also a meta-analysis, this mostly dry cows, all lactating cows. So that might have some effect. But the biggest thing is, is the amount of magnesium in the diets. And the blue line here outta Europe, they fed very high magnesium. The average for these studies was 45.45. We only fed 0.25. So what this is saying is you can overcome this antagonism. You, you won't ever eliminate it, but you can reduce the antagonism by just feeding more and more magnesium. But, but we have equations. So you know, the dietary k, you know, the dietary magnesium, we can estimate absorption.
Dr. Bill Weiss (00:21:30):
This is more recent data from Alex Tevy out of our, out of our lab, looking at the effects of monensin. We fed high K, we wanted antagonism. We, we fed some high mag to counteract some of the antagonism. Two sources of magnesium, good, very high quality mags or mag sulfate with, or without, or 14 milligrams per kilogram dry matter monensin. We did not balance for sulfur on purpose. So sulfur may be very much involved here, but if you just look over at the scarlet bars, mag sulfate is more available than mag oxide, which we all knew. It's not that much more though this is much less than people think. It is better without monensin. When I feed monensin with mag ox absorption, increase by by more than 25%. Huge increase. When I fed monensin with meg sulfate, it decreased by a third. I, I, I think this involves the, the, the sulfur more than anything else. But for on a practical basis, we don't feed meg sulfate to lactating cows, or you really shouldn't. There's no reason to. We do feed it to dry cows and we do feed monensin to dry cows. This is a lactation diet, so I want to be careful on extrapolation, but this is suggesting if you're feeding mag sulfate and monensin to dry cows, you need to feed more magnesium to counteract this diff this drop in absorption.
Dr. Bill Weiss (00:23:07):
So with all this this new knowledge and, and different endogenous vehicles and all that, we've come up with new absorption coefficients from magnesium. These are what was in NRC. You can see diet actually is, is substantially higher, twice as high. And I should mention these numbers here are all assuming 1.2% K in the diets. So I've corrected for K this very huge variance here on absorption is because of K. So if, if you're worried about K, you might want to stick with this old, old NRC number minus one standard deviation. But you'll notice here that the, the supplements are much, much lower than old NRC, much, much lower. You're gonna say, why is that? Well, this is a mathematical thing. Remember, we can't feed magnesium free diets. So if we over, if we underestimate the availability of, of the basal, then that error has to be ec corrected for. So this is really be just because we use the wrong coefficient for diets, these I think are much more much more accurate. So Mag ox, even good Mag ox is only 25% available. Meg sulfate is only 35% available.
Dr. Bill Weiss (00:24:31):
And I, I won't go into this a lot, but we're all aware of the high variation in Mex quality. These are relative availabilities. And it went from, you know, the, the best was given a hundred percent. The worst was 10% of the best. So huge variation. This is old data, but I think this amount of variation likely still exists. There's still a lot of crappy mags out there. I get a lot of questions. Can, is there lab test? And there's the, the vinegar test, I think that might be able to rank these. I don't know if it could separate the blue from the red or the green from the purple, but it could probably definitely separate, separate the purple from the blue. But that's ranking it, it cannot quantify, it cannot say this mag is 30% available or 20%. So it might be able, this, that lab test or that vinegar test might be able to throw out these really bad ones, but it's not gonna be able to give you an absorption number. Okay, trace minerals, all I'm gonna say here is it is extremely difficult, much more difficult to measure ACS for GMs because of lots of antagonism, lots of interactions and regulated absorption. So these, these numbers are very, very have a high degree of uncertainty.
Dr. Bill Weiss (00:25:56):
The other problem with for, for trace minerals is these absorption coefficients are really low. So copper is, is somewhere between three and 5% available. And when you have a really small number in the denominator, a a a small error really adds up. And I just made an example here. I said we can have basal at 3% available, or five, we can have copper sulfate at four or six. So I'm not changing these very much. If I assume high for basil, high for copper sulfate. I only need to feed in this example about 50 milligrams of copper sulfate a day to meet requirement. If I assume low and low, I have to feed 10 times as much. So, so the these, these errors are, are, these numbers are very, are not very different. The errors are high. So just be aware that that, that a small change in these absorption coefficients for trace minerals have a huge effect on diet formulation.
Dr. Bill Weiss (00:26:59):
The other issue here is all feeds right now and the NRC system, all, all basil feeds, feed stuffs, not supplements have the same coefficient for all the trace minerals or the, the, the trace minerals would differ, but within a trace mineral, all feeds have the same absorption coefficient. We know that's not right. Here's corn silage. We know if you have corn silage with really high coppers, a lot of that copper is soil. Soil copper has almost no availability. So the absorption coefficient for this corn silage will be quite low or it's low anyway, but really low compared to this number. And we, we don't have ways to quantify that. All I can tell you is that if you have feeds and especially forages with high ash, your absorption coefficients for your tri trace minerals are likely higher than are lower than what you expect. That's all I can tell you. I can't be any more accurate than that.
Dr. Bill Weiss (00:28:02):
Antagonists, this is a list of the, the four me four main trace minerals we're worried about. The ones in red here are known antagonist. If it's red in two, two different colors, it's maybe, so sulfur is a clear antagonist for every trace mineral. Every single one single iron is kind of a, a antagonist for copper and manganese. But I'm saying it's kind of because it has to be really, really high and, and it's getting to the point where the diets we feed would not be that high. And also iron and forage is, is is not very absorbable. It's, it's almost inert, so it doesn't antagonize very much. You can see the other ones here. If, if on phosphorus, it's high phosphorus is, is affects manganese and it's by high the, the requirement actually antagonizes. If you feed the phosphorus to requirement, you are antagonizing manga, manganese. So one reason we have to feed so much manganese is because we have to meet the phosphorus requirement. So just be aware of, of these things, if you have especially red ones, increase the amounts in your diets relative availability. That's what we, we can measure that you might be able to get that number from, from companies. And it's just everything is relative though. We feed two, we measure something for coppers liver of, of the standard copper sulfate and of the product and it's the, the ratio.
Dr. Bill Weiss (00:29:42):
But I wanna emphasize the, the interactions here. This is with triassic chloride with antagonist, it was almost twice as good as copper sulfate. And in deficient animals they were the same. So you, you maybe with antagonists you see this as good higher availability, but in deficient animals just just feed copper. So be aware of all these interactions, okay? Be aware of what you're measuring. If I use colostrum as my measurement, selenium yeast is twice as good, twice as available as selenite. If I use mastitis, this is the reduction. Selenite and yeast are the same. They both reduce mastitis 10%. So be aware of the response factor.
Dr. Bill Weiss (00:30:36):
So what do you do if a company shows you data? I, my product has twice the bioavailability of copper sulfate. What do you do with copper? I adjust for availability. Just so if if their product is twice as high, I'm gonna feed half as much. Selenium, selenium yeast, it don't make any adjustment. I feed the maximum legal amount. Manganese is so poorly absorbed, I don't think it matters. And zinc, I don't a adjust if in other words, if I'm gonna feed some organic zinc, I feed the same dietary concentration, total concentration as I would with inorganic. You know, I'll explain why I do that in a little bit. This is just for your, your information. The ones in red, these are to me, these are my best guesses on revised or ingredient absorption coefficients. The ones in red are noticed, notably different from old NRC.
Dr. Bill Weiss (00:31:38):
I didn't get into manganese. I i you could, we can dig up more old data and that's why the, that's, the old, old one was about 2% and now it's down to less than 1%. So this is just for your own information. So what would you do with that, those new coefficients? Well, if you're feeding a lot of supplemental magnesium, your, your diets are gonna be higher in magnesium because the, the availability of that, that magnesium is much worse than we thought. If you're feeding a lot of supplemental calcium, for example, corn silage based diets, you're gonna probably gonna increase the calcium in your diets phosphorus, depending on, on inorganic and organic. And you're gonna feed more compared to the old NRC, you're gonna feed substantially more manganese.
Dr. Bill Weiss (00:32:28):
Okay, organic trace minerals. Are they more available? Well, I'm gonna say look at this study and the answer is yes for copper. Liver copper is a great indicator of, of status. And in this study, organic trace metal is 1.5 times as available as the inorganic. If you are using liver zinc, which is not a good status indicator, but if you use it, you're gonna assume inorganic, inorganic was the same and the same for manganese. They may or may not be, it's just that man liver manganese and liver zinc are not good status indicators. This study says organic, at least this specific organic was better. This study says just the opposite. This is liver copper. This is beef cattle. In this study the inorganic was 25% better than the organic. And all I'm gonna say is don't make these blanket assumptions that organic is always better. It depends on the product, obviously it depends on the diet, it depends on the mineral status of the cow. And you have all these interactions. So a a certain organic trace mineral might be great in this condition or this situation, but not in another one. Just, just don't think everything's the same. 'cause It's not.
Dr. Bill Weiss (00:33:49):
And this is a, a study Matt Faulkner did a couple years ago, again, showing interactions. This was hydroxy versus sulfate in a forage based diet. The hydroxy gave higher apparent copper absorption sorry, copper avail, copper balance. But when we've fed a ton of byproducts, we see just the opposite. The sulfate was superior. So again, it it depends on the product, the product, the, the value of a product depends on how you're feeding it. Do not assume everything is, is the same regardless of diets. And what I wanna finish up on is this question is absorption everything. Well, a a mineral, if it's gonna maintain body stores obviously has to be absorbed. If it's gonna go out and milk and fetus and so on, it has to be absorbed. But to maintain good health, does it have to be absorbed? And the answer is no, it does not. Some of it has to be, but not all of it. And does it, what about gut function, GI function? Does it have to be absorbed? The answer is no. There's a lot of effects of gut inside the intestine, especially on, on health.
Dr. Bill Weiss (00:35:04):
This is a summary of a lot of data here looking at sulfates versus inorganics and the hydroxy. I've combined all the data here and it's usually in these studies are feeding multiple trace minerals, copper, zinc, manganese, and, and there's five different studies here. If we look at NDF digestibility in almost every study, the sulfate was significantly or almost significantly lower. Cause lower fiber digestion, dry matter digestibility was also down in most studies with sulfate largely because of, of the drop in NDF digestion. This is likely, I think it's the sulfate is inhibiting rather than the organics. And hydroxy stimulating, I think is an inhibition. And I think it's probably mostly due to copper, but I don't know that for sure. So just be aware that of feeding high amounts of sulfates might affect energy availability of these diets.
Dr. Bill Weiss (00:36:10):
Okay, this is a study Matt did again, several years ago, or not, I guess several, but a few years ago where he fed organic zinc, inorganic zinc, same concentrations. And he, he collected fecal samples and he did this, I don't understand all this molecular biology stuff, but he did these, these things looking at for certain species of bacteria and you, you identify a gazillion different bacteria. And what he found is that the pathogen associated with digital dermatitis, and it's a tricanomis, I think when we fed the, the inner, the organic zinc, the concentration of that pathogen in the feces was lower. And so this is suggesting to us that the, the, the form of mineral that gets to the intestine is gonna affect the bacterial population in that intestine. And that that can have effects on the health. The gut is an a an extremely important immune organ. It can affect immunity not because of effects on neutrophil and and lymphocytes, but it might be in effect on, on the gut. So we, we've, and this is a, a very active area of research now, is looking at how minerals affect the microbiome in the rumen and in the intestine. So this would be totally independent of absorption.
Dr. Bill Weiss (00:37:34):
So to wrap up here remember the factorial approach only fits 50% of the population. And if you increase the 10 to 20% above the, the NRC mean, you're gonna get about 97% of the population. So feed extra 10 to 20%. We're getting better on absorption coefficients, accounting for more sources of variation, but there's still a lot of constants, which, you know, you're gonna argue why even if everything is the constant, why don't we just use diet concentrations? Well, that's a legitimate point, but it's, it's at least some, some feeds will have different AC’s. The, the supplemental sources of mineral will have a different AC than than corn or sowing. There's a ton of interactions, and this would be, this is diet and the cow, you know, the status of the cow affects absorption. Cows in generally poor status deficient animals tend to absorb more efficiently than cows in excess antagonist will affect different sources of minerals differently.
Dr. Bill Weiss (00:38:45):
A a big practical thing here is the magnesium source. The supplemental source of magnesium have extremely different availability coefficients than 2001. This was in 2001. They had, they did not have enough data to do it correctly. And so they grossly overestimated the availability. So if you're feeding a lot of supplemental magnesium because of low basal concentrations you you need to feed a lot just 'cause it's, it's so poorly absorbed for trace minerals. These are still poorly defined, but I think they are better than just using concentrations because they're at least some variation accounted for. Copper sulfate has a different absorption coefficient than corn. So that's going in the right direction. But we still have a very, very long way to go on this. And then lastly this is is the new, I'm gonna say the new frontier in mineral research is looking at the effect of minerals on gut microbiome. So just because something isn't absorbed doesn't mean it won't have some effect on that animal either positive or negative. And with that, I think I stayed pretty close to beyond time. So thank you for your attention and I'll turn it back to whoever is moderating.
Scott Sorrell (00:40:09):
All right, thank you Bill. Before we get started answering questions, we'd like to share a brief video and then we'll, we'll be right back to answer the questions submitted during today's presentation.
Commercial (00:40:19):
Our last call question is sponsored by AminoShure XM Precision Release Methionine, the next generation in amino acid balancing with AminoShure XM. You can save up to 5 cents per cal per day on your methionine investment. Try it today and receive an additional 2.50 cents per cal per day savings with Balchem’s limited time rebate offer. Contact your Balchem representative to learn more.
Scott Sorrell (00:40:44):
Dr. Weiss your first question is, how can I assess magnesium by availability in the field?
Dr. Bill Weiss (00:40:52):
One test in the field is the, the vinegar test. And, and Jesse Goff has procedures written on that. I don't remember exactly how to do it, but it's a pH putting bag s in in vinegar and looking at pH change. I'm not as big a fan of this as he is. I I I think it lacks sensitivity and it doesn't give you a number, it's just gonna say, this is good or this is higher than this. If you're really concerned, the, the, I think a, a a an application would be, or an approach would be you, you feed your diet and you collect some urine samples. And the first thing would be just to have it measured. Measure magnesium. If there's magnesium in the urine, that's telling you they're absorbing more than they need. 'cause The, the cow absorbs magnesium and then it urinates out the excess. So if you've got magnesium in the urine, it's probably saying you've got enough. But you can also, you can quantify this by you, you collect urine samples from several cows and have a lab measure urine magnesium and creatinine and, and there's equations. I I don't have it memorized, but there's equations. You look at that ratio and it's gonna tell you the apparent absorption is probably this. So we, we can actually measure that in the field with, with urine samples.
Scott Sorrell (00:42:16):
All right, our next question comes from Glen, from Wisconsin. What accounts for the large differences among Mag Ox sources?
Dr. Bill Weiss (00:42:24):
Well, ma Mag os is not a mine mineral. It's a manufactured, they, they, I don't know what the starting product is, they used to know, but they take this product and they cook it at very, very high temperatures, a thousand degrees. And that's a process called calcination. And if they cook it for too hot or too long, you get very poor abor availability. Or if they cook it at too low and too short, you get poor availability. So it's the, the temperature of the calcination, you can tell a little bit by color. If it's got a lot of burnt dark colors, it's been overcooked, but a lot of stuff looks fine, it's still not good. So calcination and, and obviously particle size. Magnesium has to be soluble to be absorbed and has to be solubilized in the rumen, which is a, you know, fairly neutral pH. So big particles are less soluble than little particles. So finer finer grind should increase availability as well. So particle size, which you can measure, and calcination, which you can't measure, are the two primary factors affecting varia affecting absorption coefficients for mag?
Scott Sorrell (00:43:44):
This is a similar question, maybe it's same answer, but coming from Jim, would, would you comment on relative magnesium availability from dolomitic limestone?
Dr. Bill Weiss (00:43:55):
The, the old data says it's, it's not very good. There's been some newer processes, so I don't know. I've seen at least I'm testimonial type things that it's better than it. We, we used to think, but the old data says it's very poor. So I'm just gonna say, I'd say in general, I would probably discount that compared to, to high quality mags. There's probably mags that's no better than that, but I good mags is likely better than, than, than Dome gly.
Scott Sorrell (00:44:32):
All right, the next one comes from Lucas. How do you pick a best mineral source when formulating a diet? For instance, magnesium sulfate or magnesium oxide? Would it be only based on price and availability?
Dr. Bill Weiss (00:44:47):
For, for the macro minerals, I, I tend to price it on cost of available mineral. Sorry. so, you know, if, if limestone one is, is has an availability of coefficient of 50 and limestone two is 40, and to do the math, but, you know, I I base it on a price available mineral, but I also base it on, on this intangible quality thing. You know, if, if there's certain mags out there and I won't go into it, you'll read my papers, you'll, you'll find what source we use. But it's consistently very good. So look for, look for just quality in, in it. And because you, you don't want something that's good, this batch is good and next batch isn't. So, so look for, look, but I think availability, quality and, and price for that, for trace minerals, it's still, it, it is still availability.
Dr. Bill Weiss (00:45:50):
But again, the, the, the inorganics will always be cheaper than the organics always. It, it, that's just the, the nature of the beast. But we've seen enough things that there's something to a lot of these organics that they do something the, the, the sulfates might be negative. So the organics, I, I base it on the literature and the literature basically says diets with organics or are these hydroxys at least with a portion of the minerals as these are worth more. So you can't just price it on, on availability coefficients for the trace minerals because you look at, you know I'm making this number up, but if you feed half, half your diet is organic trace minerals and you get a, a reduction in lameness by 10%, that's, that has huge value. So for trace minerals, I base it very heavy on what the, the research says. And, and you try and give it value to, to these, these things in addition to absorption coefficient.
Scott Sorrell (00:46:57):
Alright, thank you. Our next question comes from Fernando, how should you formulate minerals in the diet to reduce environmental pollution without losing high yields of production? What is the best way to do this?
Dr. Bill Weiss (00:47:10):
Well, you want you know, good for the macro minerals, you know, high, high availability coefficients mean you can feed less. So you would wanna pick minerals or minerals that have high avail or sources that have high availability coefficients. But when you really look at this a lot with, with a few exceptions, there's the availability coefficients vary, but the biggest impact you're gonna have is how much total mineral is in the diet. So feed this, keep your, your overfeeding, and I do, I'm a proponent of overfeeding. I don't think you should just feed the requirement, but keep the overfeeding reasonable. And 10 or 20% to me is a reasonable overfeeding. Don't feed 50% or a hundred percent over get your feeds analyzed in, include the, the minerals in the basal ingredients in your formulation. Those are available to cows. And so those, those things feed their reasonable overfeeding and, and high availability, especially for the macros.
Scott Sorrell (00:48:18):
Alright, very well. Next question comes from Jose from Florida. Why would responses to sources of trace minerals inorganics versus organics vary with the type of diet in your example, high forage versus high byproduct diets? If in general trace minerals are absorbed by metal carrier proteins, so once these trace minerals get to the small intestine, the transport system should be the same. Whether copper was original in originally in the sulfate form or associated with an organic compound.
Dr. Bill Weiss (00:48:55):
Well, the, the transport is the same, but, and the, but the mineral can be associated with something else that prevents it from being absorbed. Say copper, for example molybdenum and sulfur does not antagonize copper in, in a pig. It antagonize, its in the rumen even though the transport is the same. So you get these compounds or the substances, I don't know if they're compounds forming likely mostly in the rumen. That means that mineral, when it gets to the, the, the binding sites to the absorption sites is not available. One, one potential thing is in, in non ruminants fiber, these, these fiber tends to be negatively charged. Trace metals are positively charged. You get these associations so that the, the mineral can't, can't, isn't soluble in the, in the small intestine, it's bound to these fiber particles. So a lot of it is the, the, I'm gonna say the form of mineral that actually gets to the small intestine.
Dr. Bill Weiss (00:49:57):
And that's where these antagonists come in and where the form, the source of the mineral affects it. So it's, it's if, if the mineral soluble and the intestine and available, it doesn't matter. Well, I should, I'm gonna back up a minute. It mostly doesn't matter. But there's also data, and this is with pigs or with actually with cells pig cells showing that some of these transporters in the intestine actually absorb the, they don't absorb the metal, they absorb the complex. The, in this case it was zinc methionine and zinc glycinate, I think. And we always thought that it was the, the, just the metal they were absorbing. But anyway, the cell culture data saying that in some situations it's actually absorbing the, the complex and that complex once in the cell is handled differently than the, than the bare metal. So it has to do with the, the form or the, the association of the mineral with other compounds in the, in the intestine or in the digesta. And then it might be the me the formin is absorbed and may may matter more than we thought.
Scott Sorrell (00:51:11):
Alright, very well Jim is asking, do you believe the ratio of potassium to magnesium is a significant metric in lactating rations over and above the concentration of each individual mineral?
Dr. Bill Weiss (00:51:25):
No, I'm, I'm not a big fan of ratios. Because both the, the numerator, you can change a ratio by changing the numerator and or the denominator. And those should have very different effects. We, we know high K means you have to feed more magnesium, we know that, but I don't know if it's a certain ratio. We have equations too. So I'd say, you know, you, you feed, if you, you, the way i I do typical diets is, you know, the for for not for lactating cows is I decide do I wanna supplement K for, for added milk fat? If I don't, then you know, our diets are gonna be 1.4% K typically 1.2, 1.4% K I use the, this equation we have and I've come up with the absorption coefficient for magnesium. If I want to supplement K and get these diet Ks up to 2% or so, two and a half percent for milk fat, then, then I again use this equation. The ratio is different, I is different. So I'd say those equations I showed you are, are the better approach than, than a ratio. But realize that as K goes up, you always have to feed more magnesium. The antagonism of of magnesium with potassium starts below the potassium requirement. So you don't have, you could feed a diet that's deficient in potassium and it will still antagonize magnesium absorption.
Scott Sorrell (00:53:00):
Alright. All right. Next question comes from Bill. Why do you think Monin has such an apparent effect on magnesium absorption based on magnesium source?
Dr. Bill Weiss (00:53:11):
Well, likely has a lot to do with potassium. And then the source one, like I said, that was a big, we actually thought we'd get the exact, our hypothesis was exactly opposite of what we, what we found. 'cause We th we know magnesium sulfate is more soluble in the rumen, solubility drives drives absorption. So we thought with scent is, is likely a, again, this pa this potassium effect because to absorb magnesium in the room and K is K is involved and k is also affects monensin and affects K. So the this this high sulfur thing is, like I said, I think if, and I, if I stand around, I do this experiment, but it's, I don't think it's magnesium sulfate. I think I could have got the same thing if I would've fed mag ox and sodium sulfate, just elevate the sulfur. And again, I think it has to do with potassium interactions now with sulfur. It, it's, there's other people with, especially with sheep have shown mega with, with rumensin mag absorption is increased magnesium absorption from mags is increased. That's been shown with, with sheep and feedlot cattle. So that was kind of expected, but this, this, this high sulfur thing wa was not, and again, I think it's not a mag sulfate thing. I think it's a sulfate thing.
Scott Sorrell (00:54:45):
Alright. Mike from Wisconsin is asking, does NRC values have a 10 or 20% over requirement? And do you add to these base values?
Dr. Bill Weiss (00:54:56):
In, in theory NRC is averaged it's, there's no safety factor whatsoever. You know, some averages are better than other averages. You know, some averages might be two studies, but the NRC numbers are, would, would fit the average cal at least, again, realizing the limitation of the data. But there is no, no safety factor in NRC
Scott Sorrell (00:55:26):
One is asking what is the best form of potassium in case of heat stress?
Dr. Bill Weiss (00:55:32):
Well, you might get different answers, but, but you know, if, if for heat stress, I think K chloride or K carbonate K carbonate is probably a little better because of some buffering issues. But it, it's in my opinion, one of the biggest reasons you should feed high K in heat stress is not to cover the, the sweat loss, which is there, but I don't think that's that big. But one thing pot potassium does is it makes cows pee a lot. They urinate a lot and if they urinate a lot, that means they have to drink a lot. And it, it's a heat flux. You know, you drink cold water, you urinate out hot water, so you can remove a lot of water, a lot of heat out of a cow by really stimulating urination. And again, potassium is very, very good at doing it. Sodium is two, but potassium is really good at that. And to increase urination, it doesn't matter, the source does not matter. K carbonate has the, the benefits of, of higher milk fat, et cetera. KK chloride, you don't usually see that. So I'd say for heat stress, if all, if all you really want is, is the heat stress and because of cost, I'd probably go with K chloride. But I realize K carbonate has some added benefits on milk fat and room and buffering.
Scott Sorrell (00:56:57):
Dr. Weiss, I see that we're at the top of the hour right now, but we have a lot of questions. In fact we're, we're not gonna get to all of 'em today. Just wondering if you have a few more minutes for a, a few more questions. Yep.
Dr. Bill Weiss (00:57:08):
Yeah, I can take a few more minutes.
Scott Sorrell (00:57:10):
Alright. Very well. Ruby is asking does ration software count in the magnesium availability in this C-N-C-P-S model?
Dr. Bill Weiss (00:57:22):
I'm gonna have say, I don't know. My guess is probably not, I'm not aware of, of too many models that incorporate antagonism and they need to, and we, again, we've gotten much better on this. So I, I might, you'd have to check with someone at, at, at Cornell or read the book, but I doubt it does NRC does not. Spartan does not. So I I doubt it does. But there the, you, there's equations that could be incorporated into it. Or you can incorporate, you know, do the calculations yourself, but I, my guess is it does not. But if someone knows, please correct me
Scott Sorrell (00:58:00):
Very well. Next one comes from Michael. What are your views on importance of calcium bioavailability and what is the best methods for measuring availability?
Dr. Bill Weiss (00:58:13):
Well, for a lactating cow within reason, you know, I'm not gonna get too excited about calcium availability 'cause limestone's cheap and, you know, you can feed a little bit extra dry, dry cows and fresh cows. It's a different situation, but I don't get too excited about about it. You, you don't want something so poor where you have to feed a bunch of it and it's a nerd and takes up, takes up space. We don't have a good way to measure availability of calcium. You know, because, you know, if we can measure fecal calcium, but calcium absorption is regulated and so you feed a whole high calcium diets apparent absorption is gonna be low. You feed low calcium diets, apparent absorption is gonna be high. So I really don't think there's a, a way to assess actual availability in the past. And I don't know if, if anybody even does this anymore.
Dr. Bill Weiss (00:59:08):
There was this pH for limestone anyway, looking at, at how, how the limestone would affect pH in a lab and that had to do with then if it, if it really altered the pH it was a, an active limestone and was was a better maybe buffer, but I think on just bioavailability of, of calcium, I don't know of a, of a field test and even measuring it in a research situation is very poor or very difficult. But again, I think if you just buy good limestone, good particle size, you probably are gonna be okay for lactating cows.
Scott Sorrell (00:59:49):
Alright, thank you. Two more because of an antagonism. Should I alter trace mineral supplementation when feeding sulfate based ionic salts to prefetch cows?
Dr. Bill Weiss (01:00:02):
That's a good question. And we know that, you know, if you're using, using anion salts and sulfates, we know you're gonna be getting up to 0.4% sulfur and at 0.4 sulfur, I guarantee you are reduced copper absorption, you have reduced selenium absorption. You guarantee it. The question is, is does it matter for two or three weeks? And for selenium, there actually was a study quite a while ago where they, they had a, the prefs was only two weeks and it, and they were looking at, at selenium status of the cow and, and, and of the newborn calf. And it didn't, the, the two week high sulfur diet did not affect measures of selenium status. So I think, and, and for copper, you know, we feed so much copper and livers are, and most of these cows have more than adequate copper. So even if you've reduced copper absorption by 50% for three weeks, I don't think it's a big deal.
Dr. Bill Weiss (01:01:06):
If you were feeding anion salts the entire dry period, that's a, that's a different issue then I would be concerned, especially with selenium. But for a two or three week free refresh at 0.4 sulfur, make sure that all the cows are fed adequate all the time. But I don't think I'd worry too much about increasing concentrations for that short presh period. You might think about for selenium, you and i, I do this anyway, but you might think about putting at least half or so a a good, a goodly portion of the selenium from yeast rather than all selenite if you're feeding the, the sulfate.
Scott Sorrell (01:01:48):
Alright, and I think this is a good one to end on. Having served on the last two dairy NRC committees, what are the top two to three research studies that are needed relative to mineral requirements in dairy cattle?
Dr. Bill Weiss (01:02:03):
Well, I said I think we're getting on, on, on the macros. I think we're getting pretty good on those and I think the requirements, and they, they're, they, if you look over time, they, they're pretty much on the tweaking side. Trace minerals are, is, is more difficult. I'm just gonna say I'd like we clearly need, if we're gonna go to absorb minerals, which I should, we need studies looking at availability from ingredients, not not supplements. Manganese concentrations of ingredients vary widely. Is the availability coefficients of corn different from alfalfa or whatever? We have no idea. None, none whatsoever. So a few studies like that would be useful. And then the problem with the NRC approach is it's, it's this factorial thing and you, you look at, okay, we're replacing everything that the cow loses every day, but is that really, you know, if, if we're having these effects in the gut, if you feed just to meet the requirement, is that enough to see these microbiome effects?
Dr. Bill Weiss (01:03:15):
So there's a lot, a lot we still don't know about non, what I'm gonna say, non factorial effects of minerals like, like this, this this effects of on fiber digestion, what are these different minerals doing for the rumen we have with molecular biology techniques now we can do so much more than we could 10 or 20 years ago. And I know people are looking at this, so I think to look at things other than milk repro or fetal growth growth, you know, look at what else do minerals do that we do not account for in, in the factorial system.
Scott Sorrell (01:03:59):
All right. On behalf of Balchem and Dr. Weiss, thank you for joining us today.
Commercial (01:04:05):
We'd love to hear your comments or ideas for topics and guests. So please reach out via email@anh.marketing at balchem.com with any suggestions and we'll work hard to add them to the schedule. Don't forget to leave a five star rating on your way out. You can request your Real Science Exchange t-shirt in just a few easy steps, just like or subscribe to the Real Science Exchange. And send us a screenshot along with your address and t-shirt size to anh.marketing at balchem.com. Balchem’s Real Science Lecture series of webinars takes place on the first Tuesday of every month with the top research and nutrition topics that will impact your business. We also include small ruminant, monogastric, and companion animal focused topics throughout the year. Visit balchem.com/realscience to see the upcoming topics and to register for future webinars. You can also access Past webinars and search for the topics most important to you.