Zinc for Goats

Zinc deficiency is often suspected when a goat is losing hair, but there are other reasons for hair loss, and that is not the only symptom of zinc deficiency. In this episode, we are talking about zinc with Dr. Robert VanSaun from the Department of Veterinary and Biomedical Sciences at Pennsylvania State University. 

First, he talks about how zinc affects 200 different functions in the body, and it is unfortunately deficient in all forage in the U.S. Goats need at least 40 ppm zinc in their diet, but most forage is closer to 25 ppm. 

Then we discuss interactions with other minerals and how too much of some minerals can cause a zinc deficiency.

Full show notes here --- https://thriftyhomesteader.com/zinc-for-goats/

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Transcript

Introduction  0:03 
For the love of goats! We are talking about everything goat. Whether you're a goat owner, a breeder, or just a fan of these wonderful creatures, we've got you covered. And now, here is Deborah Niemann.

Deborah Niemann  0:18 
Hello, everyone, and welcome to today's episode. I am really excited today to be joined once again by Dr. Robert Van Saun from Pennsylvania State University in the Department of Veterinary and Biomedical Sciences. And, the last two times he was on, we talked about selenium and copper. If you missed those episodes, I hope you'll go back and listen to them; we'll put a link in the show notes for you. And today, we are talking about a mineral that gets a lot of attention, also, and that is zinc—zinc deficiency in goats. Welcome to the show, Dr. Van Saun.

Robert Van Saun  0:57 
Thank you very much, Deborah, and glad to be here again!

Deborah Niemann  1:00 
So first of all, just to get started, could you go ahead and just tell us why is zinc important to goats and what can happen if they don't get enough of it?

Robert Van Saun  1:10 
Well, zinc is important to everybody, including goats. And, when we think about our what we call "trace minerals"—so we previously talked about selenium and copper. Zinc is part of the trace mineral package. It's required in milligrams per day, as opposed to, say, calcium or phosphorus that are in grams per day. So, that's 1000-fold difference. What's really important with zinc is that zinc affects over 200 to 300 different proteins and enzymes in our body. It is essential for cell replication, because it is required for the enzymes that replicate DNA and RNA, the two building blocks in genetic codes. And it's also extremely important in our immune response, as evidenced by, you know, many commercial products out there that you buy—throat lozenges and everything—where they highlight extra zinc, or zinc tablets. And zinc also is very important in our taste; one of the first things that disappears in zinc deficiency is your ability to discriminate tastes. And so that results in a decrease in intake, then, of course, that's going to further accelerate, you know, a poor growth rate or anything in a younger animal, a younger goat kid. And lastly, the hair and the skin are very important metabolically active tissues that are constantly growing, and hence very associated with the availability of zinc.

Deborah Niemann  3:07 
That's awesome. And so then, if a goat becomes deficient in zinc, what are some of the symptoms that people will see?

Robert Van Saun  3:15 
Well, what's described in the literature in humans, as well as what's observed in most animals, kind of the first thing is they start to back off their feed. And that's probably associated with this loss of smell and taste ability. And then probably the next thing that we start to see is some scruffiness to the hair coat, some maybe excessive exfoliation or so in the skin, you know, typical patchy skin kind of problems. This may lead to—depending on the severity of the deficiency—to a very unique disease process that is only associated with zinc deficiency. And this is called "parakeratosis." And what this is, is the cornified cells that are the surface of our skin, they normally lose their nucleus as they become cornified cells, and then they slough off over time, you know, and so that's sort of the ongoing flaking part of the skin. And in a healthy animal, that occurs and keeps the skin fairly healthy and pliant. In parakeratosis, what happens is you get a thickening of the keratin layer, and then, if we look at it under the microscope, we can see that the nuclei remain in these keratin cells. And so that's a unique process that is exclusively associated with zinc deficiency, and it was first discovered in pigs and associated with high calcium intakes in pigs.

Deborah Niemann  5:03 
Wow, that is really interesting! So, I know a lot of people think that, "Oh, if my goat is zinc deficient, I just need to give it more zinc." But I personally am always looking for the cause. And like, let's not just throw something at this, because a lot of times zinc deficiency is actually caused by interactions with other minerals. I know, in my case, quite a long time ago—I think it's been well over 10 years ago now—I could not get any grass hay one year. And all I had was alfalfa hay. And then, in January of that winter, my bucks were losing huge patches of hair, so much so that I put a T-shirt on one of them, because I thought he was gonna freeze to death, because he was missing, like, six-inch-wide patches of hair. And then one day I walked out there, and everybody was foaming at the mouth; it looked like somebody had sprayed whipped cream all over the stall, and I put the feed—the alfalfa—in the hay feeder. And they all just looked at me. Like, nobody even took a step towards it. And I was like, "Oh my gosh, my hay is bad. They've all been poisoned." And this was back in the days when I was still really new. I loaded up all these bucks in my little minivan, which was quite a stinky experience, to drive them two hours to the university, to find out why they were all refusing to eat. And I was told that they were zinc deficient, because they had been getting a diet of 100% alfalfa for over two months at that point. And so it was an interaction with the high calcium in their diet, and that I just needed to somehow find some grass hay for them to help them with that problem.

Robert Van Saun  6:55 
Yeah, so of course, the first thing we do need to think about when we start to see hair coat problems is external parasites—so lice and things like that—especially during the winter months, and so on. But most certainly, the hair coat and the skin are very much affected by nutrition in many different ways. We could go on for many, many hours in discussing what factors... I mean, of course, protein can have an effect. But the key ones—you know, copper, zinc, vitamin A, vitamin E—these are all major players of our kind of lesser-looked-at minerals and vitamins that could impact hair coat and skin quality. But certainly zinc would be high on the list. And, as you mentioned, zinc does have a fair number of interactions that can result in problems.

Robert Van Saun  8:00 
And there's another unique interaction, probably beyond our discussion for today. But zinc is very important in vitamin A function. Zinc is required for the liver to produce a protein that carries vitamin A through the body, and vitamin A is very important for skin health and hair coat. So, there could be a secondary interaction. We haven't talked too much about this, but vitamin A is one of the challenge vitamins in our ruminant species, because vitamin A can be broken down in the rumen to quite an extent. So, even with supplementation, depending on how much grain you're feeding in your diet, you could actually see a significant degradation of vitamin A. And any stored forage is going to be very low in vitamin A. And, on top of that, zinc is actually the single most important deficiency in all our forages; all our forages are, for the most part, right at or below basic requirements of maintenance for most species. And so, zinc is the one trace element that we absolutely need to have some kind of supplementation on top of a forage diet to ensure adequate zinc intake.

Deborah Niemann  9:32 
Wow, that is really good to know, because a lot of minerals are actually quite low in zinc, unfortunately.

Robert Van Saun  9:40 
Yeah. You know, again, the surveys that have been done, and looking at the forage libraries—the Dairy One lab in Ithaca, New York, or the Cumberland Valley lab down in Waynesboro, Pennsylvania—have zinc in grasses, usually will run somewhere in the range of 15 to 25 parts per million on a dry weight basis. And in alfalfa, it might be slightly higher, up to about 25 or 30 parts per million. But, in many cases, we're looking at a requirement that's about 40 parts per million.

Deborah Niemann  10:20 
Wow, okay.

Robert Van Saun  10:21 
So, a forage-only diet is not going to be zinc adequate.

Deborah Niemann  10:25 
That is an excellent point to make. Because I think a lot of people, if they have goats that are just pets, or raising meat goats that are out on pasture all the time, they may not understand that it's still really important for them to have a mineral that has a good amount of zinc in it.

Robert Van Saun  10:43 
That's correct.

Deborah Niemann  10:43 
I definitely want to talk about the zinc in minerals in a minute. But, let's finish talking about the possible antagonists for zinc in a goat's diet. So, high alfalfa—because bucks don't need calcium like milkers and pregnant does and stuff. So, that can be a problem in dry does and bucks. But what are some of the other minerals that can cause an antagonist issue?

Robert Van Saun  11:09 
Right, so we do need to remember in bucks and wethers, we do want to maintain at least a 2:1 calcium to phosphorus ratio. So, you know, we don't want to go below that, otherwise we're going to have urinary calculi problems that we don't want. But, if we feed too much calcium, we can also see, you know, calcium carbonate crystals and so on. But yes, calcium will interfere. Now, zinc. As an atom, zinc has what we call a "+2 charge." And I bring that up not to try and be scientific, but just for people to appreciate how sophisticated the body and the absorption process is, and how specific it is. Zinc has to be in the +2 valence—as we call it—to be absorbed. If it's not, if it's elemental zinc, a 0 valence, or something else—something altered—it can't be absorbed by the transporters. So, all of our trace elements are absorbed in the small intestine; they're not absorbed in the rumen, or even in the abomasum. And depending on the form of zinc, it can be altered in the rumen by the bugs, where some negative charges can be added to it, making it less soluble, less available, or it can be altered in the abomasum, with the low pH, and that could again alter charges. So for zinc, like any trace element, to be absorbed, it's got to be in the right balance, and it's got to be soluble in water.

Robert Van Saun  12:49 
So that's another important point is right above the, what we call the "brush border," on the cells that line our intestine, there's a water or aqueous layer, and the zinc has to be solubilized in that water later for it to be connected to the transporter that'll pull it into the cell. And so, zinc has two different types of transporters. There is a fairly zinc-specific transporter, and then there's what's called a divalent cation transporter. So that's where zinc can compete with copper, iron, and some other elements for transport. So, what we need to be thinking about is we need to keep everything in balance. If we respond, as we talked about, right at the very beginning, "Oh, we see hair problems, let's throw a lot more zinc into the issue." That could upset the balance in the gut in terms of absorption, because if you feed too much zinc, the cells actually produce a protein within the cell body—it's the cell cytoplasm—that binds zinc, making it unavailable to be transported into the blood. So, if we have high levels of zinc, zinc stimulates protein to be synthesized in this, in the intestinal cells, called "metallothioneins." This binds the zinc, doesn't let it go, and these cells get sloughed off every two to three days. And so, if we feed really high levels of zinc, we actually are inducing a reduction in the absorption efficiency of zinc. Now, the problem is, is other elements, like copper and iron, can also stimulate production of this metallothionein. So, if we have copper in excess in the diet relative to zinc, or high iron from water, or something like that, this could stimulate the production of this protein that will then bind zinc, even if it's in low quantities, making it unavailable to be transported into the blood, or there's competition for those transporters to bring zinc into the cell. So, iron and copper would be my two biggest concerns beyond calcium. There is some indication that aluminum, and maybe even phosphorus, can interfere with zinc availability, depending on their levels in the respective diet.

Deborah Niemann  15:33 
It's interesting, I had not heard about aluminum and phosphorus before. How would a goat get too much of that in their diet?

Robert Van Saun  15:41 
Well, in terms of the aluminum, this would be associated with aluminum contamination of soils and ultimately high aluminum that might be in plant tissue.

Deborah Niemann  15:51 
Okay.

Robert Van Saun  15:51 
And in terms of phosphorus, that would be excess phosphorus supplementation in the diet, you know, through excessive use of byproduct feeds, like wheat mids and things like that. So like, one of the concerns that we look at when I look at labels and reading labels of various concentrate or grain products or mineral products, is I do look at that phosphorus and calcium-phosphorus and look at the ingredient list and if wheat mids, as well as—

Deborah Niemann  16:24 
So you're saying "wheat middlings"?

Robert Van Saun  16:26 
Yeah, wheat middlings, wheat mids, wheat bran, soy, soy hulls, distillers' grains—all of those things have very high phosphorus. So, those are the first, like, three ingredients. You may see that there's a fairly narrow calcium-phosphorus ratio in that product, and the phosphorus may be much higher than what we would want to see. I mean, typically, we don't need much more than 0.3% phosphorus in the diet, and some of these products can be as high as 0.6 and 0.7 and 0.8% phosphorus.

Deborah Niemann  17:03 
Oh, wow. So, I know one of the things that people ask me about quite a lot is, like, brewers' grain, because there's a lot of local breweries now, and they are happy to give you the grain for free if you just pick it up, because it saves them on disposal costs. And, based on everything you said, sounds like brewers' grain would also be high in phosphorus, too.

Robert Van Saun  17:24 
Not as much, but it is up there. But, because of the, you know, the other advantages of one, of free food—you never want to turn down a free food. But if you do use something like that, then you got to be more conscious about where the other phosphorus sources might be and not, you know, complement that with a high-phosphorus mineral product or a high-phosphorus grain product.

Deborah Niemann  17:51 
Okay, that's really great to know. I've always just kind of said, "We've got free brewers' grain, and we feed it to our pigs and chickens, but I won't give it to my goats," because I just hadn't seen anything—I haven't seen any research on it being fed to goats. And you know, if it's not broke, don't fix it. My goats are doing well. And so, I'm really afraid to upset the applecart.

Robert Van Saun  18:13 
Well, I don't blame you there. I, as I tell my students, you know, the first rule of nutrition is never fix anything that isn't broke. And so, that's where, I think, many people get themselves into trouble, is they get caught up in some new product being marketed that touts all kinds of things. And then they add that to their diet and not, you know, appreciating what imbalances might be induced through these things. That all being said, brewers' grains is a very, very good food resource for our ruminant animals. It's got very good fermentable fiber in it; it's got what we call "bypass proteins," so it provides good amino acids to the gut for the goat or the animal to absorb. And that can complement a very soluble protein that might be in pasture or something like that, in terms of meeting the absolute amino acid or protein requirements of say, a late pregnant animal or a lactating animal.

Deborah Niemann  19:19 
So, as with all the other minerals, the number one most important first step is to make sure that you have a really high-quality goat mineral that has the zinc in it and everything else that they need. So, I know this varies based upon the amount of salt—we've talked about that before—because when we're talking about ppm and percentages, those are concentrations. And so, if you've got 20% salt in something, you're going to need a lot less of a mineral than if it's 90% salt, because the goats are going to eat a lot less of it if there's 90% salt than if there's only 20% salt. And an awful lot of minerals are, like, in that 15 to 20% number. So, if somebody's got about a 20% salt in their mineral, is there a minimum level of zinc that people should not go below?

Robert Van Saun  20:14 
I would be hesitant to go below about 1,000 parts per million.

Deborah Niemann  20:20 
Okay. And one of the things that I think can confuse people if they are trying to be conscientious and reading the labels is that some labels... Well, for zinc, some of them will have a percentage and some will have "ppm." And so, can you talk about that mathematical formula there?

Robert Van Saun  20:41 
Yeah. So, that's really a big challenge. And again, one of the issues in nutrition that sort of turns people off about understanding nutrition is there's too much math involved. So, a part per million, or ppm, is a concentration, you know, just like a percent is a concentration. A percent is 1 in 100, and a part per million is, as the name implies, 1 in a million. To convert those two, the easiest way to remember is, when you compare a percent to a part per million, the actual number should be larger on a part per million basis. So, in other words, let's say 1%. To change that to parts per million, you would move the decimal point. So you have 1.0; you move the decimal point four spots to the right. So, from a percentage, to convert that to a part per million, you need to make it a larger number. So 1%, if you add four 0s to that, becomes 10,000 parts per million. So that's a fairly large number for zinc, 1%. Now again, the animals don't eat percentages, they don't eat parts per million, they they eat amounts—milligrams per day. And so, it all comes back down to how much grams or milligrams of salt product or other product it has. If we go the other way... So, let's say we have 1,000 parts per million of zinc; we want to convert that to a percent. Now we have to move it four decimal places to the left, so we have to make it a smaller number. So that becomes 0.1%.

Deborah Niemann  22:50 
Thank you. Hopefully, that will help people a lot. I know, I must have Googled that conversion a dozen times before it finally stuck in my head. And I like the way that you explained it. If somebody had explained it to me like that in the beginning, I think I would've—I don't think I would have had to Google that so many times.

Robert Van Saun  23:08 
No, and it is a challenge, and just remembering which direction you go and things like that. But it's just a matter of moving the decimal point four places.

Deborah Niemann  23:18 
Excellent. So, once somebody realizes that they have a zinc deficiency problem... Well, the first thing I tell people is, "If you know that... Like, if you've got a buck that you're feeding alfalfa to, just stop feeding the alfalfa. Like, I've noticed that with my bucks; I really do my best to get as much grass hay for them now as I can. And if I can't get enough, I stretch it using grass hay pellets for them during the winter. But I also know that, you know, if they start to show some symptoms, like, in March, I don't worry about it too much, because I know that within two weeks of putting them on pasture in April that it's all going to clear up once that gets balanced again.

Robert Van Saun  24:02 
Another thing, Deborah, in terms of the alfalfa that I want to bring out, but alfalfa contains a fair amount of what we call "oxalates." And there's also another compound in many plants called "phytate." Now, the rumen has microbial enzymes that can break these things down most of the time, but it's not 100% efficient, but oxalate and phytates are very strong binders—or what we call "chelaters"—of divalent cations. So zinc is very much absorbed into oxalates and phytates. So, this is a big problem in our nonruminant species, but it may account for some of the alfalfa issues. It may not necessarily only be calcium, but it may also be the presence of oxalates. And so, we need to think about that. There's many plants out there, as goats go out and graze in pastures—unless you've got a pure grass pasture and they're not getting into other plants—there's a lot of weeds out there that contain a fair amount of oxalates, and there's potential phytates in almost any plant source that we have. So, there's those issues that we need to think about, also, that could affect zinc absorption and zinc availability to the goat.

Deborah Niemann  25:36 
Oh, that is really fascinating. Thank you for sharing that.

Robert Van Saun  25:40 
And the other thing: I know many goat people are so focused, as appropriately, on parasite control. And I know there's a lot of interest in the use of copper wire particle boluses, not only to provide copper to the goat, but to also provide an effect against the Haemonchus parasite in the abomasum. The problem there is, you know, the copper oxide wire particles, they produce a massive amount of copper ions that compete with zinc for absorption. So, if you're using these copper wire particle boluses either for some copper supplementation and/or worm control, you better be cognizant of what impact it's having on on zinc.

Deborah Niemann  26:37 
That's a great point. In fact, one of the things that I see so much with wethers is people will contact me about their wether that just looks horrible, is in terrible shape, and I find... I'm like, "Okay, well what are you feeding them, and what mineral do they have available?" And they send me a list of, like, six or seven things that they're giving this wether. And it's like, wethers are, like, the easiest keepers in the world. And they are literally killing them with kindness. And my first recommendation is like, "Okay, just stop all of it."

Robert Van Saun  27:13  
Back off.

Deborah Niemann  27:15  
Like, okay, this one mineral is good, like, just leave that one mineral out there, stop everything else. And let's see how they look—like, you've got pictures here—let's see how they look in a couple months, when they are just getting this one goat mineral in addition to their forage. And it's amazing how many people send me pictures, and send back in a couple months, and say, "Oh my gosh, they are in great shape. Now they look beautiful. Their hair is beautiful. They're doing great." Because they were just overdoing it. 

Robert Van Saun  27:47  
Well, that's my point, you know, everything in nutrition needs to be in balance. Every nutrient, every essential nutrient for our body, potentially could induce a deficiency disease or toxicity disease. And that toxicity disease could be a direct toxicity, like we talked about previously with copper, or with selenium, or it could be a secondary intoxication, like we talked about when we discussed copper, where molybdenum—high molybdenum—could induce, you know, copper deficiency. So that's kind of a secondary toxicity type issue, molybdenum toxicity. So, we just need to remember that everything should be in balance, and a good guideline—although there's a fair amount of what I'll call "wiggle room" around it—but I usually try to keep my zinc-to-copper ratio at about 4:1 in the diet. Now, again, that could be plus or minus, you know, one, one and a half, or so. But if I start to see zinc, you know, where people are really supplementing really, really high levels of zinc, that's going to have a negative effect on copper availability, and it's going to decrease zinc absorption efficiency, so you're spending a lot of money on this, you know, special zinc supplement and not getting the benefit out of it. And then vice versa, if we're feeling a little more copper, especially through these boluses, and not accounting for that in our diet relative to the zinc, that could be suppressing zinc availability, leading to zinc deficiency. And then, you know, we've talked about iron, we talked about, you know, manganese, calcium, oxalates, phytates. They all can be additive in the diet. So, it may not be one big thing, but it could be a combination of those things. And that's where nutrition gets a little more complicated is we need to look at everything and look at it all in balance rather than, you know, focusing on one thing.

Deborah Niemann  29:56  
Right. So like, for example, on our farm, we've got high iron and sulfur in our well water, which causes a problem with copper absorption, so we give copper oxide, which, if you give too much of that... And I think that's where it can wind up—it can become additive for our bucks. It's, like, the combination of the extra copper, along with the calcium and oxalates in the alfalfa, so it's a cumulative thing where the bucks... It's only our bucks that show symptoms of zinc deficiency, in the winter, if they happen to be getting too much alfalfa.

Robert Van Saun  30:32  
And you mentioned sulfur, and we didn't bring that up, but one of the things that happens is sulfates in the water, once they get into the rumen, the rumen bugs can make things like copper sulfide, and zinc sulfide. Those two compounds are completely nonsoluble. And so, basically, they'll just flow on out through the feces and never be absorbed. So, you think you're feeding the zinc, but you can make zinc sulfide that, in the rumen, under the environment of the rumen, and the microbes, under the right conditions, we can actually increase the zinc sulfide, resulting in insoluble—and remember I said the zinc's got to be soluble. And zinc sulfide doesn't break apart.

Deborah Niemann  31:22  
That is really good to know. Thank you. Alright, so somebody, their animals are showing symptoms of zinc deficiency; they've looked at, like, the other minerals in the diet to see if they can eliminate anything that might be causing an antagonist situation. They can't find anything. So, they want to add some extra zinc to the diet. What's the best way to do that?

Robert Van Saun  31:47  
So, the challenge would be, we can add inorganic zinc sources; the best are zinc oxide or zinc sulfate. Problem is, is those things are so concentrated that you would need to add such a miniscule amount that, you know, you would either end up over-supplementing in some way. And it's just challenging to add just mineral on top of, you know, forage or something like that. So, one option would be to look at labels and try and find something that is a little higher in zinc. And then, I would also encourage people to read the ingredient list and see what kind of form that the zinc is in within the product. So, when we talk about minerals, we talk about inorganic minerals, which is basically rock. Of course, animals don't like eating rocks, necessarily. And so those are typically our sulphate forms, our oxide forms, our carbonate forms, okay? So those are inorganic mineral sources. So, typically on the label, you're going to see "zinc oxide" or "zinc sulfate." Might occasionally see "zinc carbonate." Those inorganic forms are highly susceptible to these interactions that we talked about, especially in the rumen. So, even if you do go and get some inorganic and add it, you know, you may have to add more than what you think you need to, just because of some of its going to get altered in the rumen. Yeah, this rumen is a wonderful system for our animals to make them, you know, sustainably productive for us in our environment; they can survive on things that we can't eat, and live in regions that we can't grow. But it does provide some challenges from a nutritional standpoint and how these microbes can alter. 

Robert Van Saun  33:54  
So this gets us into a new area. We talked about this, I think, a little bit with selenium—is organic forms of minerals. Right? So organic forms is where the metal ion is linked in some way to another compound, whether that be an amino acid, or a partial protein, or a carbohydrate, or something along those lines. One of the long-standing products that has been out here, and very well studied over the years, is the line of products that comes from a company in Minnesota called Zinpro: Z-I-N-P-R-O. They produce amino acid chelate. So, they have zinc that's bound to the compound methionine, which is an essential amino acid. Now, what typically is promoted by the companies that make these organic minerals is that they have, or they cite, higher bioavailability, and they usually suggest that, for example, methionine being an amino acid, there's an active transporter for that, the zinc comes along. That's not the case. Again, zinc has to be separated from the methionine to be absorbed, unlike what we talked about with selenium, where the selenium was actually incorporated into the methionine compound and replaced the sulfur. What I do think is beneficial from organic minerals is they're more protected in the rumen. By having that methionine wrapped around the zinc and bound to the zinc, it's less available to be acted upon by the environment of the rumen to form zinc sulfides or be bound by oxalates and stuff. So then, once this compound comes down to the abomasum, the low pH usually separates the compound, and then that makes free zinc ion available. 

Robert Van Saun  36:12  
So, given what we talked about relative to trying to keep things in balance, and if we feed too much zinc to try and make up for deficiency, I might think about, in these cases, top dressing, or adding a little bit of zinc methionine—or a similar product. There's hydroxylated zinc, and there's some others. And you could do this through a treat, you know, you can mix it in some applesauce, or you could just mix it in with the grain or something like that. And we're only talking about a fairly small amount, you know, a gram and a half, two grams, three grams, depending on the product. And I think having some organic form, in a situation where you're seeing the zinc deficiency signs, most likely, you're not going to get to the bottom of what all the interactions are, because, as we said, there may be multiple interactions. And so most of these take place in the rumen. And if we can bypass that rumen, so to speak, with a protected zinc form, I think we would have a much better effect.

Deborah Niemann  37:23  
Wow, this is also fascinating. And, as usual, I really appreciate this. I love how you explain everything so fully, because I really like to know, like, the why behind everything, you know, and like, I know that loss of appetite is a symptom of zinc deficiency, but I didn't know it was because they lose their sense of taste and smell. I mean, that totally makes sense. 

Deborah Niemann  37:45  
Is there anything else that you want to add that people need to know about zinc before we wrap up for today?

Robert Van Saun  37:51  
I think those were really the key points. So, you know, what I would look at in labels is, as we said, if you're looking at a mineral product, you know, I certainly would not want to see anything less than 1,000 parts per million zinc; I would certainly be much higher. Most of them are usually in the 5,000 or 5,500 range. And again, the amount of zinc is going to depend on the animal; a growing animal needs more zinc, and a lactating animal needs more zinc because her metabolism is higher, than a wether, or, you know, kind of a maintenance animal. We've got to think about the interactions. And we need to remember that zinc is so interconnected with so many of the other elements; we don't want to get into this "if a little is good, a lot is better" kind of approach to supplementing zinc in the diet. And, we need to remember this very important calcium and copper interaction with zinc. Think about that 4:1 ratio—in the total diet, that is—and then consider the use of organic forms of zinc, like zinc methionine, or zinc proteinate, or zinc hydroxylase, or something like that, that protects it a bit in the rumen. Especially if you're feeding a higher grain diet. You're feeding those animals for growth, or for a late pregnancy lactation. You know, I would certainly want to add a bypass organic mineral source rather than just throwing more and more zinc in. 

Robert Van Saun  39:36  
The only other thing to talk about with this is we know from clinical signs, with hair changes and so on, about zinc concerns. The question, and something that I've emphasized in my previous talks, is we need to also have a little more science behind this. And so we've talked about measuring copper or selenium in blood or in liver. Zinc is a little bit of a challenge here. We can measure zinc in blood and interpret those values. We can measure zinc in liver tissue and interpret those values. But it's not as sensitive to the diet as what we would like to see. So, if a herd is having ongoing problems with hair coat and so on, I would advocate that I would probably want to get some blood samples and measure zinc concentrations and see if they're really low. But, we also know that zinc in the blood, or even in the liver, isn't near as diagnostic as our other trace elements. So we are a little handicapped from that perspective.

Deborah Niemann  40:50  
Oh, that is really good to know, because now that you've mentioned it, I've never heard anybody talk about doing any kind of testing to see if an animal is zinc deficient. So, it's good to know that it's not that great of an indicator of whether or not you have a problem. And your summary of everything was excellent! So thank you for that. 

Robert Van Saun  41:09  
All right. 

Deborah Niemann  41:10  
This has been a really great conversation. I think it's going to be really helpful to a lot of people, and hopefully it clears up a lot of misconceptions about zinc. Thanks for joining us today. 

Robert Van Saun  41:20  
Thank you so much. 

Deborah Niemann  41:22  
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